* [PATCH v6 00/17] Improve generic string routines
@ 2023-01-10 21:00 Adhemerval Zanella
2023-01-10 21:00 ` [PATCH v6 01/17] Parameterize op_t from memcopy.h Adhemerval Zanella
` (16 more replies)
0 siblings, 17 replies; 26+ messages in thread
From: Adhemerval Zanella @ 2023-01-10 21:00 UTC (permalink / raw)
To: libc-alpha, Noah Goldstein, Richard Henderson
It is done by:
1. parametrizing the internal routines (for instance the find zero
in a word) so each architecture can reimplement without the need
to reimplement the whole routine.
2. vectorizing more string implementations (for instance strcpy
and strcmp).
3. Change some implementations to use already possible optimized
ones (for instance strnlen). It makes new ports to focus on
only provide optimized implementation of a hardful symbols
(for instance memchr) and make its improvement to be used in
a larger set of routines.
For the rest of #5806 I think we can handle them later and if
performance of generic implementation is closer I think it is better
to just remove old assembly implementations.
I also checked on x86_64-linux-gnu, i686-linux-gnu, powerpc-linux-gnu,
and powerpc64-linux-gnu by removing the arch-specific assembly
implementation and disabling multiarch (it covers both LE and BE
for 64 and 32 bits). I also checked the string routines on alpha, hppa,
and sh.
Changes since v5:
* Replace 'inline' with '__always_inline' macros.
* Replace strchr implementation with a simpler one that call
strchrnul.
* Add strchrnul suggested changes.
* Add memchr suggested changes.
* Added check_mask on string-maskoff.h.
* Rebase and update Copyright years.
Changes since v4:
* Removed __clz and __ctz in favor of count_leading_zero and
count_trailing_zeros from longlong.h.
* Use repeat_bytes more often.
* Added a comment on strcmp final_cmp on why index_first_zero_ne can
not be used.
Changes since v3:
* Rebased against master.
* Dropped strcpy optimization.
* Refactor strcmp implementation.
* Some minor changes in comments.
Changes since v2:
* Move string-fz{a,b,i} to its own patch.
* Add a inline implementation for __builtin_c{l,t}z to avoid using
compiler provided symbols.
* Add a new header, string-maskoff.h, to handle unaligned accesses
on some implementation.
* Fixed strcmp on LE machines.
* Added a unaligned strcpy variant for architecture that define
_STRING_ARCH_unaligned.
* Add SH string-fzb.h (which uses cmp/str instruction to find
a zero in word).
Changes since v1:
* Marked ChangeLog entries with [BZ #5806], as appropriate.
* Reorganized the headers, so that armv6t2 and power6 need override
as little as possible to use their (integer) zero detection insns.
* Hopefully fixed all of the coding style issues.
* Adjusted the memrchr algorithm as discussed.
* Replaced the #ifdef STRRCHR etc that are used by the multiarch
* files.
* Tested on i386, i686, x86_64 (verified this is unused), ppc64,
ppc64le --with-cpu=power8 (to use power6 in multiarch), armv7,
aarch64, alpha (qemu) and hppa (qemu).
Adhemerval Zanella (1):
Parameterize op_t from memcopy.h
Adhemerval Zanella Netto (10):
Add string-maskoff.h generic header
Add string vectorized find and detection functions
string: Improve generic strlen
string: Improve generic strnlen
string: Improve generic strchr
string: Improve generic strchrnul
string: Improve generic strcmp
string: Improve generic memchr
string: Improve generic memrchr
sh: Add string-fzb.h
Richard Henderson (6):
Parameterize OP_T_THRES from memcopy.h
hppa: Add memcopy.h
hppa: Add string-fzb.h and string-fzi.h
alpha: Add string-fzb.h and string-fzi.h
arm: Add string-fza.h
powerpc: Add string-fza.h
string/memchr.c | 171 +++++-----------
string/memcmp.c | 4 -
string/memrchr.c | 189 +++---------------
string/strchr.c | 159 +--------------
string/strchrnul.c | 153 ++------------
string/strcmp.c | 119 +++++++++--
string/strlen.c | 90 ++-------
string/strnlen.c | 137 +------------
sysdeps/alpha/string-fzb.h | 52 +++++
sysdeps/alpha/string-fzi.h | 113 +++++++++++
sysdeps/arm/armv6t2/string-fza.h | 70 +++++++
sysdeps/generic/memcopy.h | 10 +-
sysdeps/generic/string-extbyte.h | 37 ++++
sysdeps/generic/string-fza.h | 102 ++++++++++
sysdeps/generic/string-fzb.h | 49 +++++
sysdeps/generic/string-fzi.h | 135 +++++++++++++
sysdeps/generic/string-maskoff.h | 84 ++++++++
sysdeps/generic/string-opthr.h | 25 +++
sysdeps/generic/string-optype.h | 24 +++
sysdeps/hppa/memcopy.h | 42 ++++
sysdeps/hppa/string-fzb.h | 70 +++++++
sysdeps/hppa/string-fzi.h | 139 +++++++++++++
sysdeps/i386/i686/multiarch/strnlen-c.c | 14 +-
sysdeps/i386/memcopy.h | 3 -
sysdeps/i386/string-opthr.h | 25 +++
sysdeps/m68k/memcopy.h | 3 -
sysdeps/powerpc/powerpc32/power4/memcopy.h | 5 -
.../powerpc32/power4/multiarch/memchr-ppc32.c | 14 +-
.../power4/multiarch/strchrnul-ppc32.c | 4 -
.../power4/multiarch/strnlen-ppc32.c | 14 +-
.../powerpc64/multiarch/memchr-ppc64.c | 9 +-
sysdeps/powerpc/string-fza.h | 70 +++++++
sysdeps/s390/strchr-c.c | 11 +-
sysdeps/s390/strchrnul-c.c | 2 -
sysdeps/s390/strlen-c.c | 10 +-
sysdeps/s390/strnlen-c.c | 14 +-
sysdeps/sh/string-fzb.h | 54 +++++
sysdeps/x86_64/x32/string-optype.h | 24 +++
38 files changed, 1397 insertions(+), 853 deletions(-)
create mode 100644 sysdeps/alpha/string-fzb.h
create mode 100644 sysdeps/alpha/string-fzi.h
create mode 100644 sysdeps/arm/armv6t2/string-fza.h
create mode 100644 sysdeps/generic/string-extbyte.h
create mode 100644 sysdeps/generic/string-fza.h
create mode 100644 sysdeps/generic/string-fzb.h
create mode 100644 sysdeps/generic/string-fzi.h
create mode 100644 sysdeps/generic/string-maskoff.h
create mode 100644 sysdeps/generic/string-opthr.h
create mode 100644 sysdeps/generic/string-optype.h
create mode 100644 sysdeps/hppa/memcopy.h
create mode 100644 sysdeps/hppa/string-fzb.h
create mode 100644 sysdeps/hppa/string-fzi.h
create mode 100644 sysdeps/i386/string-opthr.h
create mode 100644 sysdeps/powerpc/string-fza.h
create mode 100644 sysdeps/sh/string-fzb.h
create mode 100644 sysdeps/x86_64/x32/string-optype.h
--
2.34.1
^ permalink raw reply [flat|nested] 26+ messages in thread
* [PATCH v6 01/17] Parameterize op_t from memcopy.h
2023-01-10 21:00 [PATCH v6 00/17] Improve generic string routines Adhemerval Zanella
@ 2023-01-10 21:00 ` Adhemerval Zanella
2023-01-10 21:00 ` [PATCH v6 02/17] Parameterize OP_T_THRES " Adhemerval Zanella
` (15 subsequent siblings)
16 siblings, 0 replies; 26+ messages in thread
From: Adhemerval Zanella @ 2023-01-10 21:00 UTC (permalink / raw)
To: libc-alpha, Noah Goldstein, Richard Henderson
It moves the op_t definition out to an specific header, adds
the attribute 'may-alias', and cleanup its duplicated definitions.
Checked with a build and check with run-built-tests=no for all major
Linux ABIs.
---
string/memcmp.c | 1 -
sysdeps/generic/memcopy.h | 6 ++----
sysdeps/generic/string-optype.h | 24 ++++++++++++++++++++++++
sysdeps/x86_64/x32/string-optype.h | 24 ++++++++++++++++++++++++
4 files changed, 50 insertions(+), 5 deletions(-)
create mode 100644 sysdeps/generic/string-optype.h
create mode 100644 sysdeps/x86_64/x32/string-optype.h
diff --git a/string/memcmp.c b/string/memcmp.c
index 067b2e6a42..ea0fa03e1c 100644
--- a/string/memcmp.c
+++ b/string/memcmp.c
@@ -46,7 +46,6 @@
/* Type to use for aligned memory operations.
This should normally be the biggest type supported by a single load
and store. Must be an unsigned type. */
-# define op_t unsigned long int
# define OPSIZ (sizeof (op_t))
/* Threshold value for when to enter the unrolled loops. */
diff --git a/sysdeps/generic/memcopy.h b/sysdeps/generic/memcopy.h
index 9f3ffb5d30..b5ffa4d114 100644
--- a/sysdeps/generic/memcopy.h
+++ b/sysdeps/generic/memcopy.h
@@ -55,10 +55,8 @@
[I fail to understand. I feel stupid. --roland]
*/
-/* Type to use for aligned memory operations.
- This should normally be the biggest type supported by a single load
- and store. */
-#define op_t unsigned long int
+/* Type to use for aligned memory operations. */
+#include <string-optype.h>
#define OPSIZ (sizeof (op_t))
/* Type to use for unaligned operations. */
diff --git a/sysdeps/generic/string-optype.h b/sysdeps/generic/string-optype.h
new file mode 100644
index 0000000000..42bdd2a145
--- /dev/null
+++ b/sysdeps/generic/string-optype.h
@@ -0,0 +1,24 @@
+/* Define a type to use for word access. Generic version.
+ Copyright (C) 2023 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#ifndef _STRING_OPTYPE_H
+#define _STRING_OPTYPE_H 1
+
+typedef unsigned long int __attribute__ ((__may_alias__)) op_t;
+
+#endif /* string-optype.h */
diff --git a/sysdeps/x86_64/x32/string-optype.h b/sysdeps/x86_64/x32/string-optype.h
new file mode 100644
index 0000000000..e7679f934f
--- /dev/null
+++ b/sysdeps/x86_64/x32/string-optype.h
@@ -0,0 +1,24 @@
+/* Define a type to use for word access. Generic version.
+ Copyright (C) 2023 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#ifndef _STRING_OPTYPE_H
+#define _STRING_OPTYPE_H 1
+
+typedef unsigned long long int __attribute__ ((__may_alias__)) op_t;
+
+#endif /* string-optype.h */
--
2.34.1
^ permalink raw reply [flat|nested] 26+ messages in thread
* [PATCH v6 02/17] Parameterize OP_T_THRES from memcopy.h
2023-01-10 21:00 [PATCH v6 00/17] Improve generic string routines Adhemerval Zanella
2023-01-10 21:00 ` [PATCH v6 01/17] Parameterize op_t from memcopy.h Adhemerval Zanella
@ 2023-01-10 21:00 ` Adhemerval Zanella
2023-01-10 21:00 ` [PATCH v6 03/17] Add string-maskoff.h generic header Adhemerval Zanella
` (14 subsequent siblings)
16 siblings, 0 replies; 26+ messages in thread
From: Adhemerval Zanella @ 2023-01-10 21:00 UTC (permalink / raw)
To: libc-alpha, Noah Goldstein, Richard Henderson; +Cc: Carlos O'Donell
From: Richard Henderson <richard.henderson@linaro.org>
It moves OP_T_THRES out of memcopy.h to its own header and adjust
each architecture that redefines it.
Checked with a build and check with run-built-tests=no for all major
Linux ABIs.
Co-authored-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
---
string/memcmp.c | 3 ---
sysdeps/generic/memcopy.h | 4 +---
sysdeps/generic/string-opthr.h | 25 ++++++++++++++++++++++
sysdeps/i386/memcopy.h | 3 ---
sysdeps/i386/string-opthr.h | 25 ++++++++++++++++++++++
sysdeps/m68k/memcopy.h | 3 ---
sysdeps/powerpc/powerpc32/power4/memcopy.h | 5 -----
7 files changed, 51 insertions(+), 17 deletions(-)
create mode 100644 sysdeps/generic/string-opthr.h
create mode 100644 sysdeps/i386/string-opthr.h
diff --git a/string/memcmp.c b/string/memcmp.c
index ea0fa03e1c..047ca4f98e 100644
--- a/string/memcmp.c
+++ b/string/memcmp.c
@@ -48,9 +48,6 @@
and store. Must be an unsigned type. */
# define OPSIZ (sizeof (op_t))
-/* Threshold value for when to enter the unrolled loops. */
-# define OP_T_THRES 16
-
/* Type to use for unaligned operations. */
typedef unsigned char byte;
diff --git a/sysdeps/generic/memcopy.h b/sysdeps/generic/memcopy.h
index b5ffa4d114..e9b3f227b2 100644
--- a/sysdeps/generic/memcopy.h
+++ b/sysdeps/generic/memcopy.h
@@ -57,6 +57,7 @@
/* Type to use for aligned memory operations. */
#include <string-optype.h>
+#include <string-opthr.h>
#define OPSIZ (sizeof (op_t))
/* Type to use for unaligned operations. */
@@ -188,9 +189,6 @@ extern void _wordcopy_bwd_dest_aligned (long int, long int, size_t)
#endif
-/* Threshold value for when to enter the unrolled loops. */
-#define OP_T_THRES 16
-
/* Set to 1 if memcpy is safe to use for forward-copying memmove with
overlapping addresses. This is 0 by default because memcpy implementations
are generally not safe for overlapping addresses. */
diff --git a/sysdeps/generic/string-opthr.h b/sysdeps/generic/string-opthr.h
new file mode 100644
index 0000000000..6f10a98edd
--- /dev/null
+++ b/sysdeps/generic/string-opthr.h
@@ -0,0 +1,25 @@
+/* Define a threshold for word access. Generic version.
+ Copyright (C) 2023 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#ifndef _STRING_OPTHR_H
+#define _STRING_OPTHR_H 1
+
+/* Threshold value for when to enter the unrolled loops. */
+#define OP_T_THRES 16
+
+#endif /* string-opthr.h */
diff --git a/sysdeps/i386/memcopy.h b/sysdeps/i386/memcopy.h
index 4f82689b84..1aa7c3a850 100644
--- a/sysdeps/i386/memcopy.h
+++ b/sysdeps/i386/memcopy.h
@@ -18,9 +18,6 @@
#include <sysdeps/generic/memcopy.h>
-#undef OP_T_THRES
-#define OP_T_THRES 8
-
#undef BYTE_COPY_FWD
#define BYTE_COPY_FWD(dst_bp, src_bp, nbytes) \
do { \
diff --git a/sysdeps/i386/string-opthr.h b/sysdeps/i386/string-opthr.h
new file mode 100644
index 0000000000..ed3e4b2ddb
--- /dev/null
+++ b/sysdeps/i386/string-opthr.h
@@ -0,0 +1,25 @@
+/* Define a threshold for word access. i386 version.
+ Copyright (C) 2018 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#ifndef I386_STRING_OPTHR_H
+#define I386_STRING_OPTHR_H 1
+
+/* Threshold value for when to enter the unrolled loops. */
+#define OP_T_THRES 8
+
+#endif /* I386_STRING_OPTHR_H */
diff --git a/sysdeps/m68k/memcopy.h b/sysdeps/m68k/memcopy.h
index accd81c1c3..610577071d 100644
--- a/sysdeps/m68k/memcopy.h
+++ b/sysdeps/m68k/memcopy.h
@@ -20,9 +20,6 @@
#if defined(__mc68020__) || defined(mc68020)
-#undef OP_T_THRES
-#define OP_T_THRES 16
-
/* WORD_COPY_FWD and WORD_COPY_BWD are not symmetric on the 68020,
because of its weird instruction overlap characteristics. */
diff --git a/sysdeps/powerpc/powerpc32/power4/memcopy.h b/sysdeps/powerpc/powerpc32/power4/memcopy.h
index 384f33b029..872157e485 100644
--- a/sysdeps/powerpc/powerpc32/power4/memcopy.h
+++ b/sysdeps/powerpc/powerpc32/power4/memcopy.h
@@ -50,11 +50,6 @@
[I fail to understand. I feel stupid. --roland]
*/
-
-/* Threshold value for when to enter the unrolled loops. */
-#undef OP_T_THRES
-#define OP_T_THRES 16
-
/* Copy exactly NBYTES bytes from SRC_BP to DST_BP,
without any assumptions about alignment of the pointers. */
#undef BYTE_COPY_FWD
--
2.34.1
^ permalink raw reply [flat|nested] 26+ messages in thread
* [PATCH v6 03/17] Add string-maskoff.h generic header
2023-01-10 21:00 [PATCH v6 00/17] Improve generic string routines Adhemerval Zanella
2023-01-10 21:00 ` [PATCH v6 01/17] Parameterize op_t from memcopy.h Adhemerval Zanella
2023-01-10 21:00 ` [PATCH v6 02/17] Parameterize OP_T_THRES " Adhemerval Zanella
@ 2023-01-10 21:00 ` Adhemerval Zanella
2023-01-11 1:58 ` Richard Henderson
2023-01-10 21:00 ` [PATCH v6 04/17] Add string vectorized find and detection functions Adhemerval Zanella
` (13 subsequent siblings)
16 siblings, 1 reply; 26+ messages in thread
From: Adhemerval Zanella @ 2023-01-10 21:00 UTC (permalink / raw)
To: libc-alpha, Noah Goldstein, Richard Henderson; +Cc: Adhemerval Zanella Netto
From: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
Macros to operate on unaligned access for string operations:
- create_mask: create a mask based on pointer alignment to sets up
non-zero bytes before the beginning of the word so a following
operation (such as find zero) might ignore these bytes.
- check_mask: eturn the mask WORD shifted based on S_INT address
value, to ignore values not presented in the aligned word read.
- repeat_bytes: setup an word with each byte being c_in.
- highbit_mask: create a mask with high bit of each byte being 1,
and the low 7 bits being all the opposite of the input.
- word_containing: return the address of the op_t word containing the
addres.
These macros are meant to be used on optimized vectorized string
implementations.
---
sysdeps/generic/string-maskoff.h | 85 ++++++++++++++++++++++++++++++++
1 file changed, 85 insertions(+)
create mode 100644 sysdeps/generic/string-maskoff.h
diff --git a/sysdeps/generic/string-maskoff.h b/sysdeps/generic/string-maskoff.h
new file mode 100644
index 0000000000..6ad4e0b6f9
--- /dev/null
+++ b/sysdeps/generic/string-maskoff.h
@@ -0,0 +1,85 @@
+/* Mask off bits. Generic C version.
+ Copyright (C) 2023 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#ifndef _STRING_MASKOFF_H
+#define _STRING_MASKOFF_H 1
+
+#include <endian.h>
+#include <limits.h>
+#include <stdint.h>
+#include <string-optype.h>
+#include <string-fza.h>
+
+/* Provide a mask based on the pointer alignment that sets up non-zero
+ bytes before the beginning of the word. It is used to mask off
+ undesirable bits from an aligned read from an unaligned pointer.
+ For instance, on a 64 bits machine with a pointer alignment of
+ 3 the function returns 0x0000000000ffffff for LE and 0xffffff0000000000
+ (meaning to mask off the initial 3 bytes). */
+static __always_inline op_t
+create_mask (uintptr_t i)
+{
+ i = i % sizeof (op_t);
+ if (__BYTE_ORDER == __LITTLE_ENDIAN)
+ return ~(((op_t)-1) << (i * CHAR_BIT));
+ else
+ return ~(((op_t)-1) >> (i * CHAR_BIT));
+}
+
+/* Return the mask WORD shifted based on S_INT address value, to ignore
+ values not presented in the aligned word read. */
+static __always_inline op_t
+check_mask (op_t word, uintptr_t s_int)
+{
+ if (__BYTE_ORDER == __LITTLE_ENDIAN)
+ return word >> (CHAR_BIT * (s_int % sizeof (s_int)));
+ else
+ return word << (CHAR_BIT * (s_int % sizeof (s_int)));
+}
+
+/* Setup an word with each byte being c_in. For instance, on a 64 bits
+ machine with input as 0xce the functions returns 0xcececececececece. */
+static __always_inline op_t
+repeat_bytes (unsigned char c_in)
+{
+ return ((op_t)-1 / 0xff) * c_in;
+}
+
+/* Based on mask created by 'create_mask', mask off the high bit of each
+ byte in the mask. It is used to mask off undesirable bits from an
+ aligned read from an unaligned pointer, and also taking care to avoid
+ match possible bytes meant to be matched. For instance, on a 64 bits
+ machine with a mask created from a pointer with an alignment of 3
+ (0x0000000000ffffff) the function returns 0x7f7f7f0000000000 for BE
+ and 0x00000000007f7f7f for LE. */
+static __always_inline op_t
+highbit_mask (op_t m)
+{
+ return m & repeat_bytes (0x7f);
+}
+
+/* Return the address of the op_t word containing the address P. For
+ instance on address 0x0011223344556677 and op_t with size of 8,
+ it returns 0x0011223344556670. */
+static __always_inline op_t *
+word_containing (char const *p)
+{
+ return (op_t *) ((uintptr_t) p & -sizeof(p));
+}
+
+#endif /* _STRING_MASKOFF_H */
--
2.34.1
^ permalink raw reply [flat|nested] 26+ messages in thread
* [PATCH v6 04/17] Add string vectorized find and detection functions
2023-01-10 21:00 [PATCH v6 00/17] Improve generic string routines Adhemerval Zanella
` (2 preceding siblings ...)
2023-01-10 21:00 ` [PATCH v6 03/17] Add string-maskoff.h generic header Adhemerval Zanella
@ 2023-01-10 21:00 ` Adhemerval Zanella
2023-01-11 2:25 ` Richard Henderson
2023-01-10 21:00 ` [PATCH v6 05/17] string: Improve generic strlen Adhemerval Zanella
` (12 subsequent siblings)
16 siblings, 1 reply; 26+ messages in thread
From: Adhemerval Zanella @ 2023-01-10 21:00 UTC (permalink / raw)
To: libc-alpha, Noah Goldstein, Richard Henderson; +Cc: Adhemerval Zanella Netto
From: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
This patch adds generic string find and detection meant to be used in
generic vectorized string implementation. The idea is to decompose the
basic string operation so each architecture can reimplement if it
provides any specialized hardware instruction.
The 'string-fza.h' provides zero byte detection functions (find_zero_low,
find_zero_all, find_eq_low, find_eq_all, find_zero_eq_low, find_zero_eq_all,
find_zero_ne_low, and find_zero_ne_all). They are used on both functions
provided by 'string-fzb.h' and 'string-fzi'.
The 'string-fzb.h' provides boolean zero byte detection with the
functions:
- has_zero: determine if any byte within a word is zero.
- has_eq: determine byte equality between two words.
- has_zero_eq: determine if any byte within a word is zero along with
byte equality between two words.
The 'string-fzi.h' provides zero byte detection along with its positions:
- index_first_zero: return index of first zero byte within a word.
- index_first_eq: return index of first byte different between two words.
- index_first_zero_eq: return index of first zero byte within a word or
first byte different between two words.
- index_first_zero_ne: return index of first zero byte within a word or
first byte equal between two words.
- index_last_zero: return index of last zero byte within a word.
- index_last_eq: return index of last byte different between two words.
Co-authored-by: Richard Henderson <richard.henderson@linaro.org>
---
sysdeps/generic/string-extbyte.h | 37 +++++++++
sysdeps/generic/string-fza.h | 102 +++++++++++++++++++++++
sysdeps/generic/string-fzb.h | 49 +++++++++++
sysdeps/generic/string-fzi.h | 135 +++++++++++++++++++++++++++++++
sysdeps/generic/string-maskoff.h | 9 +--
5 files changed, 327 insertions(+), 5 deletions(-)
create mode 100644 sysdeps/generic/string-extbyte.h
create mode 100644 sysdeps/generic/string-fza.h
create mode 100644 sysdeps/generic/string-fzb.h
create mode 100644 sysdeps/generic/string-fzi.h
diff --git a/sysdeps/generic/string-extbyte.h b/sysdeps/generic/string-extbyte.h
new file mode 100644
index 0000000000..38b4674dca
--- /dev/null
+++ b/sysdeps/generic/string-extbyte.h
@@ -0,0 +1,37 @@
+/* Extract by from memory word. Generic C version.
+ Copyright (C) 2023 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#ifndef _STRING_EXTBYTE_H
+#define _STRING_EXTBYTE_H 1
+
+#include <limits.h>
+#include <endian.h>
+#include <string-optype.h>
+
+/* Extract the byte at index IDX from word X, with index 0 being the
+ least significant byte. */
+static __always_inline unsigned char
+extractbyte (op_t x, unsigned int idx)
+{
+ if (__BYTE_ORDER == __LITTLE_ENDIAN)
+ return x >> (idx * CHAR_BIT);
+ else
+ return x >> (sizeof (x) - 1 - idx) * CHAR_BIT;
+}
+
+#endif /* _STRING_EXTBYTE_H */
diff --git a/sysdeps/generic/string-fza.h b/sysdeps/generic/string-fza.h
new file mode 100644
index 0000000000..1ec51f7f3c
--- /dev/null
+++ b/sysdeps/generic/string-fza.h
@@ -0,0 +1,102 @@
+/* Basic zero byte detection. Generic C version.
+ Copyright (C) 2023 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#ifndef _STRING_FZA_H
+#define _STRING_FZA_H 1
+
+#include <limits.h>
+#include <string-optype.h>
+#include <string-maskoff.h>
+
+/* This function returns non-zero if any byte in X is zero.
+ More specifically, at least one bit set within the least significant
+ byte that was zero; other bytes within the word are indeterminate. */
+static __always_inline op_t
+find_zero_low (op_t x)
+{
+ /* This expression comes from
+ https://graphics.stanford.edu/~seander/bithacks.html#ZeroInWord
+ Subtracting 1 sets 0x80 in a byte that was 0; anding ~x clears
+ 0x80 in a byte that was >= 128; anding 0x80 isolates that test bit. */
+ op_t lsb = repeat_bytes (0x01);
+ op_t msb = repeat_bytes (0x80);
+ return (x - lsb) & ~x & msb;
+}
+
+/* This function returns at least one bit set within every byte of X that
+ is zero. The result is exact in that, unlike find_zero_low, all bytes
+ are determinate. This is usually used for finding the index of the
+ most significant byte that was zero. */
+static __always_inline op_t
+find_zero_all (op_t x)
+{
+ /* For each byte, find not-zero by
+ (0) And 0x7f so that we cannot carry between bytes,
+ (1) Add 0x7f so that non-zero carries into 0x80,
+ (2) Or in the original byte (which might have had 0x80 set).
+ Then invert and mask such that 0x80 is set iff that byte was zero. */
+ op_t m = repeat_bytes (0x7f);
+ return ~(((x & m) + m) | x | m);
+}
+
+/* With similar caveats, identify bytes that are equal between X1 and X2. */
+static __always_inline op_t
+find_eq_low (op_t x1, op_t x2)
+{
+ return find_zero_low (x1 ^ x2);
+}
+
+static __always_inline op_t
+find_eq_all (op_t x1, op_t x2)
+{
+ return find_zero_all (x1 ^ x2);
+}
+
+/* With similar caveats, identify zero bytes in X1 and bytes that are
+ equal between in X1 and X2. */
+static __always_inline op_t
+find_zero_eq_low (op_t x1, op_t x2)
+{
+ return find_zero_low (x1) | find_zero_low (x1 ^ x2);
+}
+
+static __always_inline op_t
+find_zero_eq_all (op_t x1, op_t x2)
+{
+ return find_zero_all (x1) | find_zero_all (x1 ^ x2);
+}
+
+/* With similar caveats, identify zero bytes in X1 and bytes that are
+ not equal between in X1 and X2. */
+static __always_inline op_t
+find_zero_ne_low (op_t x1, op_t x2)
+{
+ return (~find_zero_eq_low (x1, x2)) + 1;
+}
+
+static __always_inline op_t
+find_zero_ne_all (op_t x1, op_t x2)
+{
+ op_t m = repeat_bytes (0x7f);
+ op_t eq = x1 ^ x2;
+ op_t nz1 = ((x1 & m) + m) | x1;
+ op_t ne2 = ((eq & m) + m) | eq;
+ return (ne2 | ~nz1) & ~m;
+}
+
+#endif /* _STRING_FZA_H */
diff --git a/sysdeps/generic/string-fzb.h b/sysdeps/generic/string-fzb.h
new file mode 100644
index 0000000000..42de500d67
--- /dev/null
+++ b/sysdeps/generic/string-fzb.h
@@ -0,0 +1,49 @@
+/* Zero byte detection, boolean. Generic C version.
+ Copyright (C) 2023 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#ifndef _STRING_FZB_H
+#define _STRING_FZB_H 1
+
+#include <endian.h>
+#include <string-fza.h>
+
+/* Determine if any byte within X is zero. This is a pure boolean test. */
+
+static __always_inline _Bool
+has_zero (op_t x)
+{
+ return find_zero_low (x) != 0;
+}
+
+/* Likewise, but for byte equality between X1 and X2. */
+
+static __always_inline _Bool
+has_eq (op_t x1, op_t x2)
+{
+ return find_eq_low (x1, x2) != 0;
+}
+
+/* Likewise, but for zeros in X1 and equal bytes between X1 and X2. */
+
+static __always_inline _Bool
+has_zero_eq (op_t x1, op_t x2)
+{
+ return find_zero_eq_low (x1, x2);
+}
+
+#endif /* _STRING_FZB_H */
diff --git a/sysdeps/generic/string-fzi.h b/sysdeps/generic/string-fzi.h
new file mode 100644
index 0000000000..b1fd4d34b3
--- /dev/null
+++ b/sysdeps/generic/string-fzi.h
@@ -0,0 +1,135 @@
+/* Zero byte detection; indexes. Generic C version.
+ Copyright (C) 2023 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#ifndef _STRING_FZI_H
+#define _STRING_FZI_H 1
+
+#include <limits.h>
+#include <endian.h>
+#include <string-fza.h>
+
+static __always_inline int
+clz (op_t c)
+{
+ if (sizeof (op_t) == sizeof (unsigned long))
+ return __builtin_clzl (c);
+ else
+ return __builtin_clzll (c);
+}
+
+static __always_inline int
+ctz (op_t c)
+{
+ if (sizeof (op_t) == sizeof (unsigned long))
+ return __builtin_ctzl (c);
+ else
+ return __builtin_ctzll (c);
+}
+
+/* A subroutine for the index_zero functions. Given a test word C, return
+ the (memory order) index of the first byte (in memory order) that is
+ non-zero. */
+static __always_inline unsigned int
+index_first (op_t c)
+{
+ int r;
+ if (__BYTE_ORDER == __LITTLE_ENDIAN)
+ r = ctz (c);
+ else
+ r = clz (c);
+ return r / CHAR_BIT;
+}
+
+/* Similarly, but return the (memory order) index of the last byte that is
+ non-zero. */
+static __always_inline unsigned int
+index_last (op_t c)
+{
+ int r;
+ if (__BYTE_ORDER == __LITTLE_ENDIAN)
+ r = clz (c);
+ else
+ r = ctz (c);
+ return sizeof (op_t) - 1 - (r / CHAR_BIT);
+}
+
+/* Given a word X that is known to contain a zero byte, return the index of
+ the first such within the word in memory order. */
+static __always_inline unsigned int
+index_first_zero (op_t x)
+{
+ if (__BYTE_ORDER == __LITTLE_ENDIAN)
+ x = find_zero_low (x);
+ else
+ x = find_zero_all (x);
+ return index_first (x);
+}
+
+/* Similarly, but perform the search for byte equality between X1 and X2. */
+static __always_inline unsigned int
+index_first_eq (op_t x1, op_t x2)
+{
+ if (__BYTE_ORDER == __LITTLE_ENDIAN)
+ x1 = find_eq_low (x1, x2);
+ else
+ x1 = find_eq_all (x1, x2);
+ return index_first (x1);
+}
+
+/* Similarly, but perform the search for zero within X1 or equality between
+ X1 and X2. */
+static __always_inline unsigned int
+index_first_zero_eq (op_t x1, op_t x2)
+{
+ if (__BYTE_ORDER == __LITTLE_ENDIAN)
+ x1 = find_zero_eq_low (x1, x2);
+ else
+ x1 = find_zero_eq_all (x1, x2);
+ return index_first (x1);
+}
+
+/* Similarly, but perform the search for zero within X1 or inequality between
+ X1 and X2. */
+static __always_inline unsigned int
+index_first_zero_ne (op_t x1, op_t x2)
+{
+ if (__BYTE_ORDER == __LITTLE_ENDIAN)
+ x1 = find_zero_ne_low (x1, x2);
+ else
+ x1 = find_zero_ne_all (x1, x2);
+ return index_first (x1);
+}
+
+/* Similarly, but search for the last zero within X. */
+static __always_inline unsigned int
+index_last_zero (op_t x)
+{
+ if (__BYTE_ORDER == __LITTLE_ENDIAN)
+ x = find_zero_all (x);
+ else
+ x = find_zero_low (x);
+ return index_last (x);
+}
+
+static __always_inline unsigned int
+index_last_eq (op_t x1, op_t x2)
+{
+ return index_last_zero (x1 ^ x2);
+}
+
+#endif /* STRING_FZI_H */
diff --git a/sysdeps/generic/string-maskoff.h b/sysdeps/generic/string-maskoff.h
index 6ad4e0b6f9..16d3cc2ddb 100644
--- a/sysdeps/generic/string-maskoff.h
+++ b/sysdeps/generic/string-maskoff.h
@@ -23,7 +23,6 @@
#include <limits.h>
#include <stdint.h>
#include <string-optype.h>
-#include <string-fza.h>
/* Provide a mask based on the pointer alignment that sets up non-zero
bytes before the beginning of the word. It is used to mask off
@@ -44,12 +43,12 @@ create_mask (uintptr_t i)
/* Return the mask WORD shifted based on S_INT address value, to ignore
values not presented in the aligned word read. */
static __always_inline op_t
-check_mask (op_t word, uintptr_t s_int)
+check_mask (op_t word, uintptr_t s)
{
if (__BYTE_ORDER == __LITTLE_ENDIAN)
- return word >> (CHAR_BIT * (s_int % sizeof (s_int)));
+ return word >> (CHAR_BIT * (s % sizeof (op_t)));
else
- return word << (CHAR_BIT * (s_int % sizeof (s_int)));
+ return word << (CHAR_BIT * (s % sizeof (op_t)));
}
/* Setup an word with each byte being c_in. For instance, on a 64 bits
@@ -79,7 +78,7 @@ highbit_mask (op_t m)
static __always_inline op_t *
word_containing (char const *p)
{
- return (op_t *) ((uintptr_t) p & -sizeof(p));
+ return (op_t *) ((op_t) p & -sizeof(p));
}
#endif /* _STRING_MASKOFF_H */
--
2.34.1
^ permalink raw reply [flat|nested] 26+ messages in thread
* [PATCH v6 05/17] string: Improve generic strlen
2023-01-10 21:00 [PATCH v6 00/17] Improve generic string routines Adhemerval Zanella
` (3 preceding siblings ...)
2023-01-10 21:00 ` [PATCH v6 04/17] Add string vectorized find and detection functions Adhemerval Zanella
@ 2023-01-10 21:00 ` Adhemerval Zanella
2023-01-10 21:00 ` [PATCH v6 06/17] string: Improve generic strnlen Adhemerval Zanella
` (11 subsequent siblings)
16 siblings, 0 replies; 26+ messages in thread
From: Adhemerval Zanella @ 2023-01-10 21:00 UTC (permalink / raw)
To: libc-alpha, Noah Goldstein, Richard Henderson; +Cc: Adhemerval Zanella Netto
From: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
New algorithm have the following key differences:
- Reads first word unaligned and use string-maskoff functions to
remove unwanted data. This strategy follow arch-specific
optimization used on powerpc, sparc, and SH.
- Use of has_zero and index_first_zero parametrized functions.
Checked on x86_64-linux-gnu, i686-linux-gnu, powerpc-linux-gnu,
and powercp64-linux-gnu by removing the arch-specific assembly
implementation and disabling multi-arch (it covers both LE and BE
for 64 and 32 bits).
Co-authored-by: Richard Henderson <richard.henderson@linaro.org>
---
string/strlen.c | 90 +++++++++--------------------------------
sysdeps/s390/strlen-c.c | 10 +++--
2 files changed, 26 insertions(+), 74 deletions(-)
diff --git a/string/strlen.c b/string/strlen.c
index ee1aae0fff..a69f3343ef 100644
--- a/string/strlen.c
+++ b/string/strlen.c
@@ -17,84 +17,34 @@
#include <string.h>
#include <stdlib.h>
-
-#undef strlen
-
-#ifndef STRLEN
-# define STRLEN strlen
+#include <stdint.h>
+#include <string-fza.h>
+#include <string-fzb.h>
+#include <string-fzi.h>
+#include <string-maskoff.h>
+
+#ifdef STRLEN
+# define __strlen STRLEN
#endif
/* Return the length of the null-terminated string STR. Scan for
the null terminator quickly by testing four bytes at a time. */
size_t
-STRLEN (const char *str)
+__strlen (const char *str)
{
- const char *char_ptr;
- const unsigned long int *longword_ptr;
- unsigned long int longword, himagic, lomagic;
-
- /* Handle the first few characters by reading one character at a time.
- Do this until CHAR_PTR is aligned on a longword boundary. */
- for (char_ptr = str; ((unsigned long int) char_ptr
- & (sizeof (longword) - 1)) != 0;
- ++char_ptr)
- if (*char_ptr == '\0')
- return char_ptr - str;
-
- /* All these elucidatory comments refer to 4-byte longwords,
- but the theory applies equally well to 8-byte longwords. */
+ /* Align pointer to sizeof op_t. */
+ const uintptr_t s_int = (uintptr_t) str;
+ const op_t *word_ptr = word_containing (str);
- longword_ptr = (unsigned long int *) char_ptr;
+ /* Read and MASK the first word. */
+ op_t word = *word_ptr | create_mask (s_int);
- /* Computing (longword - lomagic) sets the high bit of any corresponding
- byte that is either zero or greater than 0x80. The latter case can be
- filtered out by computing (~longword & himagic). The final result
- will always be non-zero if one of the bytes of longword is zero. */
- himagic = 0x80808080L;
- lomagic = 0x01010101L;
- if (sizeof (longword) > 4)
- {
- /* 64-bit version of the magic. */
- /* Do the shift in two steps to avoid a warning if long has 32 bits. */
- himagic = ((himagic << 16) << 16) | himagic;
- lomagic = ((lomagic << 16) << 16) | lomagic;
- }
- if (sizeof (longword) > 8)
- abort ();
+ while (! has_zero (word))
+ word = *++word_ptr;
- /* Instead of the traditional loop which tests each character,
- we will test a longword at a time. The tricky part is testing
- if *any of the four* bytes in the longword in question are zero. */
- for (;;)
- {
- longword = *longword_ptr++;
-
- if (((longword - lomagic) & ~longword & himagic) != 0)
- {
- /* Which of the bytes was the zero? */
-
- const char *cp = (const char *) (longword_ptr - 1);
-
- if (cp[0] == 0)
- return cp - str;
- if (cp[1] == 0)
- return cp - str + 1;
- if (cp[2] == 0)
- return cp - str + 2;
- if (cp[3] == 0)
- return cp - str + 3;
- if (sizeof (longword) > 4)
- {
- if (cp[4] == 0)
- return cp - str + 4;
- if (cp[5] == 0)
- return cp - str + 5;
- if (cp[6] == 0)
- return cp - str + 6;
- if (cp[7] == 0)
- return cp - str + 7;
- }
- }
- }
+ return ((const char *) word_ptr) + index_first_zero (word) - str;
}
+#ifndef STRLEN
+weak_alias (__strlen, strlen)
libc_hidden_builtin_def (strlen)
+#endif
diff --git a/sysdeps/s390/strlen-c.c b/sysdeps/s390/strlen-c.c
index b829ef2452..0a33a6f8e5 100644
--- a/sysdeps/s390/strlen-c.c
+++ b/sysdeps/s390/strlen-c.c
@@ -21,12 +21,14 @@
#if HAVE_STRLEN_C
# if HAVE_STRLEN_IFUNC
# define STRLEN STRLEN_C
+# endif
+
+# include <string/strlen.c>
+
+# if HAVE_STRLEN_IFUNC
# if defined SHARED && IS_IN (libc)
-# undef libc_hidden_builtin_def
-# define libc_hidden_builtin_def(name) \
- __hidden_ver1 (__strlen_c, __GI_strlen, __strlen_c);
+__hidden_ver1 (__strlen_c, __GI_strlen, __strlen_c);
# endif
# endif
-# include <string/strlen.c>
#endif
--
2.34.1
^ permalink raw reply [flat|nested] 26+ messages in thread
* [PATCH v6 06/17] string: Improve generic strnlen
2023-01-10 21:00 [PATCH v6 00/17] Improve generic string routines Adhemerval Zanella
` (4 preceding siblings ...)
2023-01-10 21:00 ` [PATCH v6 05/17] string: Improve generic strlen Adhemerval Zanella
@ 2023-01-10 21:00 ` Adhemerval Zanella
2023-01-10 21:00 ` [PATCH v6 07/17] string: Improve generic strchr Adhemerval Zanella
` (10 subsequent siblings)
16 siblings, 0 replies; 26+ messages in thread
From: Adhemerval Zanella @ 2023-01-10 21:00 UTC (permalink / raw)
To: libc-alpha, Noah Goldstein, Richard Henderson; +Cc: Adhemerval Zanella Netto
From: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
With an optimized memchr, new strnlen implementation basically calls
memchr and adjust the result pointer value.
It also cleanups the multiple inclusion by leaving the ifunc
implementation to undef the weak_alias and libc_hidden_def.
Co-authored-by: Richard Henderson <richard.henderson@linaro.org>
---
string/strnlen.c | 137 +-----------------
sysdeps/i386/i686/multiarch/strnlen-c.c | 14 +-
.../power4/multiarch/strnlen-ppc32.c | 14 +-
sysdeps/s390/strnlen-c.c | 14 +-
4 files changed, 27 insertions(+), 152 deletions(-)
diff --git a/string/strnlen.c b/string/strnlen.c
index 6ff294eab1..dc23354ec8 100644
--- a/string/strnlen.c
+++ b/string/strnlen.c
@@ -1,10 +1,6 @@
/* Find the length of STRING, but scan at most MAXLEN characters.
Copyright (C) 1991-2023 Free Software Foundation, Inc.
- Based on strlen written by Torbjorn Granlund (tege@sics.se),
- with help from Dan Sahlin (dan@sics.se);
- commentary by Jim Blandy (jimb@ai.mit.edu).
-
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation; either version 2.1 of the
@@ -20,7 +16,6 @@
not, see <https://www.gnu.org/licenses/>. */
#include <string.h>
-#include <stdlib.h>
/* Find the length of S, but scan at most MAXLEN characters. If no
'\0' terminator is found in that many characters, return MAXLEN. */
@@ -32,134 +27,12 @@
size_t
__strnlen (const char *str, size_t maxlen)
{
- const char *char_ptr, *end_ptr = str + maxlen;
- const unsigned long int *longword_ptr;
- unsigned long int longword, himagic, lomagic;
-
- if (maxlen == 0)
- return 0;
-
- if (__glibc_unlikely (end_ptr < str))
- end_ptr = (const char *) ~0UL;
-
- /* Handle the first few characters by reading one character at a time.
- Do this until CHAR_PTR is aligned on a longword boundary. */
- for (char_ptr = str; ((unsigned long int) char_ptr
- & (sizeof (longword) - 1)) != 0;
- ++char_ptr)
- if (*char_ptr == '\0')
- {
- if (char_ptr > end_ptr)
- char_ptr = end_ptr;
- return char_ptr - str;
- }
-
- /* All these elucidatory comments refer to 4-byte longwords,
- but the theory applies equally well to 8-byte longwords. */
-
- longword_ptr = (unsigned long int *) char_ptr;
-
- /* Bits 31, 24, 16, and 8 of this number are zero. Call these bits
- the "holes." Note that there is a hole just to the left of
- each byte, with an extra at the end:
-
- bits: 01111110 11111110 11111110 11111111
- bytes: AAAAAAAA BBBBBBBB CCCCCCCC DDDDDDDD
-
- The 1-bits make sure that carries propagate to the next 0-bit.
- The 0-bits provide holes for carries to fall into. */
- himagic = 0x80808080L;
- lomagic = 0x01010101L;
- if (sizeof (longword) > 4)
- {
- /* 64-bit version of the magic. */
- /* Do the shift in two steps to avoid a warning if long has 32 bits. */
- himagic = ((himagic << 16) << 16) | himagic;
- lomagic = ((lomagic << 16) << 16) | lomagic;
- }
- if (sizeof (longword) > 8)
- abort ();
-
- /* Instead of the traditional loop which tests each character,
- we will test a longword at a time. The tricky part is testing
- if *any of the four* bytes in the longword in question are zero. */
- while (longword_ptr < (unsigned long int *) end_ptr)
- {
- /* We tentatively exit the loop if adding MAGIC_BITS to
- LONGWORD fails to change any of the hole bits of LONGWORD.
-
- 1) Is this safe? Will it catch all the zero bytes?
- Suppose there is a byte with all zeros. Any carry bits
- propagating from its left will fall into the hole at its
- least significant bit and stop. Since there will be no
- carry from its most significant bit, the LSB of the
- byte to the left will be unchanged, and the zero will be
- detected.
-
- 2) Is this worthwhile? Will it ignore everything except
- zero bytes? Suppose every byte of LONGWORD has a bit set
- somewhere. There will be a carry into bit 8. If bit 8
- is set, this will carry into bit 16. If bit 8 is clear,
- one of bits 9-15 must be set, so there will be a carry
- into bit 16. Similarly, there will be a carry into bit
- 24. If one of bits 24-30 is set, there will be a carry
- into bit 31, so all of the hole bits will be changed.
-
- The one misfire occurs when bits 24-30 are clear and bit
- 31 is set; in this case, the hole at bit 31 is not
- changed. If we had access to the processor carry flag,
- we could close this loophole by putting the fourth hole
- at bit 32!
-
- So it ignores everything except 128's, when they're aligned
- properly. */
-
- longword = *longword_ptr++;
-
- if ((longword - lomagic) & himagic)
- {
- /* Which of the bytes was the zero? If none of them were, it was
- a misfire; continue the search. */
-
- const char *cp = (const char *) (longword_ptr - 1);
-
- char_ptr = cp;
- if (cp[0] == 0)
- break;
- char_ptr = cp + 1;
- if (cp[1] == 0)
- break;
- char_ptr = cp + 2;
- if (cp[2] == 0)
- break;
- char_ptr = cp + 3;
- if (cp[3] == 0)
- break;
- if (sizeof (longword) > 4)
- {
- char_ptr = cp + 4;
- if (cp[4] == 0)
- break;
- char_ptr = cp + 5;
- if (cp[5] == 0)
- break;
- char_ptr = cp + 6;
- if (cp[6] == 0)
- break;
- char_ptr = cp + 7;
- if (cp[7] == 0)
- break;
- }
- }
- char_ptr = end_ptr;
- }
-
- if (char_ptr > end_ptr)
- char_ptr = end_ptr;
- return char_ptr - str;
+ const char *found = memchr (str, '\0', maxlen);
+ return found ? found - str : maxlen;
}
+
#ifndef STRNLEN
-libc_hidden_def (__strnlen)
weak_alias (__strnlen, strnlen)
-#endif
+libc_hidden_def (__strnlen)
libc_hidden_def (strnlen)
+#endif
diff --git a/sysdeps/i386/i686/multiarch/strnlen-c.c b/sysdeps/i386/i686/multiarch/strnlen-c.c
index 351e939a93..beb0350d53 100644
--- a/sysdeps/i386/i686/multiarch/strnlen-c.c
+++ b/sysdeps/i386/i686/multiarch/strnlen-c.c
@@ -1,10 +1,10 @@
#define STRNLEN __strnlen_ia32
+#include <string/strnlen.c>
+
#ifdef SHARED
-# undef libc_hidden_def
-# define libc_hidden_def(name) \
- __hidden_ver1 (__strnlen_ia32, __GI_strnlen, __strnlen_ia32); \
- strong_alias (__strnlen_ia32, __strnlen_ia32_1); \
- __hidden_ver1 (__strnlen_ia32_1, __GI___strnlen, __strnlen_ia32_1);
+/* Alias for internal symbol to avoid PLT generation, it redirects the
+ libc_hidden_def (__strnlen/strlen) to default implementation. */
+__hidden_ver1 (__strnlen_ia32, __GI_strnlen, __strnlen_ia32);
+strong_alias (__strnlen_ia32, __strnlen_ia32_1);
+__hidden_ver1 (__strnlen_ia32_1, __GI___strnlen, __strnlen_ia32_1);
#endif
-
-#include "string/strnlen.c"
diff --git a/sysdeps/powerpc/powerpc32/power4/multiarch/strnlen-ppc32.c b/sysdeps/powerpc/powerpc32/power4/multiarch/strnlen-ppc32.c
index 957b9b99e8..2ca1cd7181 100644
--- a/sysdeps/powerpc/powerpc32/power4/multiarch/strnlen-ppc32.c
+++ b/sysdeps/powerpc/powerpc32/power4/multiarch/strnlen-ppc32.c
@@ -17,12 +17,12 @@
<https://www.gnu.org/licenses/>. */
#define STRNLEN __strnlen_ppc
+#include <string/strnlen.c>
+
#ifdef SHARED
-# undef libc_hidden_def
-# define libc_hidden_def(name) \
- __hidden_ver1 (__strnlen_ppc, __GI_strnlen, __strnlen_ppc); \
- strong_alias (__strnlen_ppc, __strnlen_ppc_1); \
- __hidden_ver1 (__strnlen_ppc_1, __GI___strnlen, __strnlen_ppc_1);
+/* Alias for internal symbol to avoid PLT generation, it redirects the
+ libc_hidden_def (__strnlen/strlen) to default implementation. */
+__hidden_ver1 (__strnlen_ppc, __GI_strnlen, __strnlen_ppc); \
+strong_alias (__strnlen_ppc, __strnlen_ppc_1); \
+__hidden_ver1 (__strnlen_ppc_1, __GI___strnlen, __strnlen_ppc_1);
#endif
-
-#include <string/strnlen.c>
diff --git a/sysdeps/s390/strnlen-c.c b/sysdeps/s390/strnlen-c.c
index 172fcc7caa..95156a0ff5 100644
--- a/sysdeps/s390/strnlen-c.c
+++ b/sysdeps/s390/strnlen-c.c
@@ -21,14 +21,16 @@
#if HAVE_STRNLEN_C
# if HAVE_STRNLEN_IFUNC
# define STRNLEN STRNLEN_C
+# endif
+
+# include <string/strnlen.c>
+
+# if HAVE_STRNLEN_IFUNC
# if defined SHARED && IS_IN (libc)
-# undef libc_hidden_def
-# define libc_hidden_def(name) \
- __hidden_ver1 (__strnlen_c, __GI_strnlen, __strnlen_c); \
- strong_alias (__strnlen_c, __strnlen_c_1); \
- __hidden_ver1 (__strnlen_c_1, __GI___strnlen, __strnlen_c_1);
+__hidden_ver1 (__strnlen_c, __GI_strnlen, __strnlen_c);
+strong_alias (__strnlen_c, __strnlen_c_1);
+__hidden_ver1 (__strnlen_c_1, __GI___strnlen, __strnlen_c_1);
# endif
# endif
-# include <string/strnlen.c>
#endif
--
2.34.1
^ permalink raw reply [flat|nested] 26+ messages in thread
* [PATCH v6 07/17] string: Improve generic strchr
2023-01-10 21:00 [PATCH v6 00/17] Improve generic string routines Adhemerval Zanella
` (5 preceding siblings ...)
2023-01-10 21:00 ` [PATCH v6 06/17] string: Improve generic strnlen Adhemerval Zanella
@ 2023-01-10 21:00 ` Adhemerval Zanella
2023-01-10 21:00 ` [PATCH v6 08/17] string: Improve generic strchrnul Adhemerval Zanella
` (9 subsequent siblings)
16 siblings, 0 replies; 26+ messages in thread
From: Adhemerval Zanella @ 2023-01-10 21:00 UTC (permalink / raw)
To: libc-alpha, Noah Goldstein, Richard Henderson; +Cc: Adhemerval Zanella Netto
From: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
New algorithm now calls strchrnul.
Checked on x86_64-linux-gnu, i686-linux-gnu, powerpc-linux-gnu,
and powerpc64-linux-gnu by removing the arch-specific assembly
implementation and disabling multi-arch (it covers both LE and BE
for 64 and 32 bits).
---
string/strchr.c | 159 ++--------------------------------------
sysdeps/s390/strchr-c.c | 11 +--
2 files changed, 14 insertions(+), 156 deletions(-)
diff --git a/string/strchr.c b/string/strchr.c
index 1572b8b42e..30c3eb10f2 100644
--- a/string/strchr.c
+++ b/string/strchr.c
@@ -21,165 +21,22 @@
<https://www.gnu.org/licenses/>. */
#include <string.h>
-#include <stdlib.h>
#undef strchr
+#undef index
-#ifndef STRCHR
-# define STRCHR strchr
+#ifdef STRCHR
+# define strchr STRCHR
#endif
/* Find the first occurrence of C in S. */
char *
-STRCHR (const char *s, int c_in)
+strchr (const char *s, int c_in)
{
- const unsigned char *char_ptr;
- const unsigned long int *longword_ptr;
- unsigned long int longword, magic_bits, charmask;
- unsigned char c;
-
- c = (unsigned char) c_in;
-
- /* Handle the first few characters by reading one character at a time.
- Do this until CHAR_PTR is aligned on a longword boundary. */
- for (char_ptr = (const unsigned char *) s;
- ((unsigned long int) char_ptr & (sizeof (longword) - 1)) != 0;
- ++char_ptr)
- if (*char_ptr == c)
- return (void *) char_ptr;
- else if (*char_ptr == '\0')
- return NULL;
-
- /* All these elucidatory comments refer to 4-byte longwords,
- but the theory applies equally well to 8-byte longwords. */
-
- longword_ptr = (unsigned long int *) char_ptr;
-
- /* Bits 31, 24, 16, and 8 of this number are zero. Call these bits
- the "holes." Note that there is a hole just to the left of
- each byte, with an extra at the end:
-
- bits: 01111110 11111110 11111110 11111111
- bytes: AAAAAAAA BBBBBBBB CCCCCCCC DDDDDDDD
-
- The 1-bits make sure that carries propagate to the next 0-bit.
- The 0-bits provide holes for carries to fall into. */
- magic_bits = -1;
- magic_bits = magic_bits / 0xff * 0xfe << 1 >> 1 | 1;
-
- /* Set up a longword, each of whose bytes is C. */
- charmask = c | (c << 8);
- charmask |= charmask << 16;
- if (sizeof (longword) > 4)
- /* Do the shift in two steps to avoid a warning if long has 32 bits. */
- charmask |= (charmask << 16) << 16;
- if (sizeof (longword) > 8)
- abort ();
-
- /* Instead of the traditional loop which tests each character,
- we will test a longword at a time. The tricky part is testing
- if *any of the four* bytes in the longword in question are zero. */
- for (;;)
- {
- /* We tentatively exit the loop if adding MAGIC_BITS to
- LONGWORD fails to change any of the hole bits of LONGWORD.
-
- 1) Is this safe? Will it catch all the zero bytes?
- Suppose there is a byte with all zeros. Any carry bits
- propagating from its left will fall into the hole at its
- least significant bit and stop. Since there will be no
- carry from its most significant bit, the LSB of the
- byte to the left will be unchanged, and the zero will be
- detected.
-
- 2) Is this worthwhile? Will it ignore everything except
- zero bytes? Suppose every byte of LONGWORD has a bit set
- somewhere. There will be a carry into bit 8. If bit 8
- is set, this will carry into bit 16. If bit 8 is clear,
- one of bits 9-15 must be set, so there will be a carry
- into bit 16. Similarly, there will be a carry into bit
- 24. If one of bits 24-30 is set, there will be a carry
- into bit 31, so all of the hole bits will be changed.
-
- The one misfire occurs when bits 24-30 are clear and bit
- 31 is set; in this case, the hole at bit 31 is not
- changed. If we had access to the processor carry flag,
- we could close this loophole by putting the fourth hole
- at bit 32!
-
- So it ignores everything except 128's, when they're aligned
- properly.
-
- 3) But wait! Aren't we looking for C as well as zero?
- Good point. So what we do is XOR LONGWORD with a longword,
- each of whose bytes is C. This turns each byte that is C
- into a zero. */
-
- longword = *longword_ptr++;
-
- /* Add MAGIC_BITS to LONGWORD. */
- if ((((longword + magic_bits)
-
- /* Set those bits that were unchanged by the addition. */
- ^ ~longword)
-
- /* Look at only the hole bits. If any of the hole bits
- are unchanged, most likely one of the bytes was a
- zero. */
- & ~magic_bits) != 0
-
- /* That caught zeroes. Now test for C. */
- || ((((longword ^ charmask) + magic_bits) ^ ~(longword ^ charmask))
- & ~magic_bits) != 0)
- {
- /* Which of the bytes was C or zero?
- If none of them were, it was a misfire; continue the search. */
-
- const unsigned char *cp = (const unsigned char *) (longword_ptr - 1);
-
- if (*cp == c)
- return (char *) cp;
- else if (*cp == '\0')
- return NULL;
- if (*++cp == c)
- return (char *) cp;
- else if (*cp == '\0')
- return NULL;
- if (*++cp == c)
- return (char *) cp;
- else if (*cp == '\0')
- return NULL;
- if (*++cp == c)
- return (char *) cp;
- else if (*cp == '\0')
- return NULL;
- if (sizeof (longword) > 4)
- {
- if (*++cp == c)
- return (char *) cp;
- else if (*cp == '\0')
- return NULL;
- if (*++cp == c)
- return (char *) cp;
- else if (*cp == '\0')
- return NULL;
- if (*++cp == c)
- return (char *) cp;
- else if (*cp == '\0')
- return NULL;
- if (*++cp == c)
- return (char *) cp;
- else if (*cp == '\0')
- return NULL;
- }
- }
- }
-
- return NULL;
+ char *r = __strchrnul (s, c_in);
+ return (*(unsigned char *)r == (unsigned char)c_in) ? r : NULL;
}
-
-#ifdef weak_alias
-# undef index
+#ifndef STRCHR
weak_alias (strchr, index)
-#endif
libc_hidden_builtin_def (strchr)
+#endif
diff --git a/sysdeps/s390/strchr-c.c b/sysdeps/s390/strchr-c.c
index c00f2cceea..90822ae0f4 100644
--- a/sysdeps/s390/strchr-c.c
+++ b/sysdeps/s390/strchr-c.c
@@ -21,13 +21,14 @@
#if HAVE_STRCHR_C
# if HAVE_STRCHR_IFUNC
# define STRCHR STRCHR_C
-# undef weak_alias
+# endif
+
+# include <string/strchr.c>
+
+# if HAVE_STRCHR_IFUNC
# if defined SHARED && IS_IN (libc)
-# undef libc_hidden_builtin_def
-# define libc_hidden_builtin_def(name) \
- __hidden_ver1 (__strchr_c, __GI_strchr, __strchr_c);
+__hidden_ver1 (__strchr_c, __GI_strchr, __strchr_c);
# endif
# endif
-# include <string/strchr.c>
#endif
--
2.34.1
^ permalink raw reply [flat|nested] 26+ messages in thread
* [PATCH v6 08/17] string: Improve generic strchrnul
2023-01-10 21:00 [PATCH v6 00/17] Improve generic string routines Adhemerval Zanella
` (6 preceding siblings ...)
2023-01-10 21:00 ` [PATCH v6 07/17] string: Improve generic strchr Adhemerval Zanella
@ 2023-01-10 21:00 ` Adhemerval Zanella
2023-01-10 21:00 ` [PATCH v6 09/17] string: Improve generic strcmp Adhemerval Zanella
` (8 subsequent siblings)
16 siblings, 0 replies; 26+ messages in thread
From: Adhemerval Zanella @ 2023-01-10 21:00 UTC (permalink / raw)
To: libc-alpha, Noah Goldstein, Richard Henderson; +Cc: Adhemerval Zanella Netto
From: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
New algorithm have the following key differences:
- Reads first word unaligned and use string-maskoff function to
remove unwanted data. This strategy follow arch-specific
optimization used on aarch64 and powerpc.
- Use string-fz{b,i} functions.
Checked on x86_64-linux-gnu, i686-linux-gnu, powerpc64-linux-gnu,
and powerpc-linux-gnu by removing the arch-specific assembly
implementation and disabling multi-arch (it covers both LE and BE
for 64 and 32 bits).
Co-authored-by: Richard Henderson <richard.henderson@linaro.org>
---
string/strchrnul.c | 153 +++---------------
.../power4/multiarch/strchrnul-ppc32.c | 4 -
sysdeps/s390/strchrnul-c.c | 2 -
3 files changed, 22 insertions(+), 137 deletions(-)
diff --git a/string/strchrnul.c b/string/strchrnul.c
index fa2db4b417..4a34a1be6e 100644
--- a/string/strchrnul.c
+++ b/string/strchrnul.c
@@ -1,10 +1,5 @@
/* Copyright (C) 1991-2023 Free Software Foundation, Inc.
This file is part of the GNU C Library.
- Based on strlen implementation by Torbjorn Granlund (tege@sics.se),
- with help from Dan Sahlin (dan@sics.se) and
- bug fix and commentary by Jim Blandy (jimb@ai.mit.edu);
- adaptation to strchr suggested by Dick Karpinski (dick@cca.ucsf.edu),
- and implemented by Roland McGrath (roland@ai.mit.edu).
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
@@ -21,146 +16,42 @@
<https://www.gnu.org/licenses/>. */
#include <string.h>
-#include <memcopy.h>
#include <stdlib.h>
+#include <stdint.h>
+#include <string-fza.h>
+#include <string-fzb.h>
+#include <string-fzi.h>
+#include <string-maskoff.h>
#undef __strchrnul
#undef strchrnul
-#ifndef STRCHRNUL
-# define STRCHRNUL __strchrnul
+#ifdef STRCHRNUL
+# define __strchrnul STRCHRNUL
#endif
/* Find the first occurrence of C in S or the final NUL byte. */
char *
-STRCHRNUL (const char *s, int c_in)
+__strchrnul (const char *str, int c_in)
{
- const unsigned char *char_ptr;
- const unsigned long int *longword_ptr;
- unsigned long int longword, magic_bits, charmask;
- unsigned char c;
-
- c = (unsigned char) c_in;
-
- /* Handle the first few characters by reading one character at a time.
- Do this until CHAR_PTR is aligned on a longword boundary. */
- for (char_ptr = (const unsigned char *) s;
- ((unsigned long int) char_ptr & (sizeof (longword) - 1)) != 0;
- ++char_ptr)
- if (*char_ptr == c || *char_ptr == '\0')
- return (void *) char_ptr;
-
- /* All these elucidatory comments refer to 4-byte longwords,
- but the theory applies equally well to 8-byte longwords. */
-
- longword_ptr = (unsigned long int *) char_ptr;
-
- /* Bits 31, 24, 16, and 8 of this number are zero. Call these bits
- the "holes." Note that there is a hole just to the left of
- each byte, with an extra at the end:
-
- bits: 01111110 11111110 11111110 11111111
- bytes: AAAAAAAA BBBBBBBB CCCCCCCC DDDDDDDD
-
- The 1-bits make sure that carries propagate to the next 0-bit.
- The 0-bits provide holes for carries to fall into. */
- magic_bits = -1;
- magic_bits = magic_bits / 0xff * 0xfe << 1 >> 1 | 1;
-
- /* Set up a longword, each of whose bytes is C. */
- charmask = c | (c << 8);
- charmask |= charmask << 16;
- if (sizeof (longword) > 4)
- /* Do the shift in two steps to avoid a warning if long has 32 bits. */
- charmask |= (charmask << 16) << 16;
- if (sizeof (longword) > 8)
- abort ();
-
- /* Instead of the traditional loop which tests each character,
- we will test a longword at a time. The tricky part is testing
- if *any of the four* bytes in the longword in question are zero. */
- for (;;)
- {
- /* We tentatively exit the loop if adding MAGIC_BITS to
- LONGWORD fails to change any of the hole bits of LONGWORD.
-
- 1) Is this safe? Will it catch all the zero bytes?
- Suppose there is a byte with all zeros. Any carry bits
- propagating from its left will fall into the hole at its
- least significant bit and stop. Since there will be no
- carry from its most significant bit, the LSB of the
- byte to the left will be unchanged, and the zero will be
- detected.
+ op_t repeated_c = repeat_bytes (c_in);
- 2) Is this worthwhile? Will it ignore everything except
- zero bytes? Suppose every byte of LONGWORD has a bit set
- somewhere. There will be a carry into bit 8. If bit 8
- is set, this will carry into bit 16. If bit 8 is clear,
- one of bits 9-15 must be set, so there will be a carry
- into bit 16. Similarly, there will be a carry into bit
- 24. If one of bits 24-30 is set, there will be a carry
- into bit 31, so all of the hole bits will be changed.
+ uintptr_t s_int = (uintptr_t) str;
+ const op_t *word_ptr = word_containing (str);
- The one misfire occurs when bits 24-30 are clear and bit
- 31 is set; in this case, the hole at bit 31 is not
- changed. If we had access to the processor carry flag,
- we could close this loophole by putting the fourth hole
- at bit 32!
+ op_t word = *word_ptr;
- So it ignores everything except 128's, when they're aligned
- properly.
+ op_t mask = check_mask (find_zero_eq_all (word, repeated_c), s_int);
+ if (mask != 0)
+ return (char *) str + index_first (mask);
- 3) But wait! Aren't we looking for C as well as zero?
- Good point. So what we do is XOR LONGWORD with a longword,
- each of whose bytes is C. This turns each byte that is C
- into a zero. */
+ do
+ word = *++word_ptr;
+ while (! has_zero_eq (word, repeated_c));
- longword = *longword_ptr++;
-
- /* Add MAGIC_BITS to LONGWORD. */
- if ((((longword + magic_bits)
-
- /* Set those bits that were unchanged by the addition. */
- ^ ~longword)
-
- /* Look at only the hole bits. If any of the hole bits
- are unchanged, most likely one of the bytes was a
- zero. */
- & ~magic_bits) != 0
-
- /* That caught zeroes. Now test for C. */
- || ((((longword ^ charmask) + magic_bits) ^ ~(longword ^ charmask))
- & ~magic_bits) != 0)
- {
- /* Which of the bytes was C or zero?
- If none of them were, it was a misfire; continue the search. */
-
- const unsigned char *cp = (const unsigned char *) (longword_ptr - 1);
-
- if (*cp == c || *cp == '\0')
- return (char *) cp;
- if (*++cp == c || *cp == '\0')
- return (char *) cp;
- if (*++cp == c || *cp == '\0')
- return (char *) cp;
- if (*++cp == c || *cp == '\0')
- return (char *) cp;
- if (sizeof (longword) > 4)
- {
- if (*++cp == c || *cp == '\0')
- return (char *) cp;
- if (*++cp == c || *cp == '\0')
- return (char *) cp;
- if (*++cp == c || *cp == '\0')
- return (char *) cp;
- if (*++cp == c || *cp == '\0')
- return (char *) cp;
- }
- }
- }
-
- /* This should never happen. */
- return NULL;
+ op_t found = index_first_zero_eq (word, repeated_c);
+ return (char *) word_ptr + found;
}
-
+#ifndef STRCHRNUL
weak_alias (__strchrnul, strchrnul)
+#endif
diff --git a/sysdeps/powerpc/powerpc32/power4/multiarch/strchrnul-ppc32.c b/sysdeps/powerpc/powerpc32/power4/multiarch/strchrnul-ppc32.c
index 88ce5dfffa..da03ac7c04 100644
--- a/sysdeps/powerpc/powerpc32/power4/multiarch/strchrnul-ppc32.c
+++ b/sysdeps/powerpc/powerpc32/power4/multiarch/strchrnul-ppc32.c
@@ -19,10 +19,6 @@
#include <string.h>
#define STRCHRNUL __strchrnul_ppc
-
-#undef weak_alias
-#define weak_alias(a,b )
-
extern __typeof (strchrnul) __strchrnul_ppc attribute_hidden;
#include <string/strchrnul.c>
diff --git a/sysdeps/s390/strchrnul-c.c b/sysdeps/s390/strchrnul-c.c
index e1248d1dbf..ff6aa38d4f 100644
--- a/sysdeps/s390/strchrnul-c.c
+++ b/sysdeps/s390/strchrnul-c.c
@@ -22,8 +22,6 @@
# if HAVE_STRCHRNUL_IFUNC
# define STRCHRNUL STRCHRNUL_C
# define __strchrnul STRCHRNUL
-# undef weak_alias
-# define weak_alias(name, alias)
# endif
# include <string/strchrnul.c>
--
2.34.1
^ permalink raw reply [flat|nested] 26+ messages in thread
* [PATCH v6 09/17] string: Improve generic strcmp
2023-01-10 21:00 [PATCH v6 00/17] Improve generic string routines Adhemerval Zanella
` (7 preceding siblings ...)
2023-01-10 21:00 ` [PATCH v6 08/17] string: Improve generic strchrnul Adhemerval Zanella
@ 2023-01-10 21:00 ` Adhemerval Zanella
2023-01-10 21:00 ` [PATCH v6 10/17] string: Improve generic memchr Adhemerval Zanella
` (7 subsequent siblings)
16 siblings, 0 replies; 26+ messages in thread
From: Adhemerval Zanella @ 2023-01-10 21:00 UTC (permalink / raw)
To: libc-alpha, Noah Goldstein, Richard Henderson; +Cc: Adhemerval Zanella Netto
From: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
New generic implementation tries to use word operations along with
the new string-fz{b,i} functions even for inputs with different
alignments (with still uses aligned access plus merge operation
to get a correct word by word comparison).
Checked on x86_64-linux-gnu, i686-linux-gnu, powerpc64-linux-gnu,
and powerpc-linux-gnu by removing the arch-specific assembly
implementation and disabling multi-arch (it covers both LE and BE
for 64 and 32 bits).
Co-authored-by: Richard Henderson <richard.henderson@linaro.org>
---
string/strcmp.c | 119 +++++++++++++++++++++++++++++++++++++++++-------
1 file changed, 103 insertions(+), 16 deletions(-)
diff --git a/string/strcmp.c b/string/strcmp.c
index 053f5a8d2b..fafd967567 100644
--- a/string/strcmp.c
+++ b/string/strcmp.c
@@ -15,33 +15,120 @@
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
+#include <stdint.h>
+#include <string-extbyte.h>
+#include <string-fzb.h>
+#include <string-fzi.h>
#include <string.h>
+#include <memcopy.h>
-#undef strcmp
-
-#ifndef STRCMP
-# define STRCMP strcmp
+#ifdef STRCMP
+# define strcmp STRCMP
#endif
+static inline int
+final_cmp (const op_t w1, const op_t w2)
+{
+ /* It can not use index_first_zero_ne because it must not compare past the
+ final '/0' is present (and final_cmp is called before has_zero check).
+ */
+ for (size_t i = 0; i < sizeof (op_t); i++)
+ {
+ unsigned char c1 = extractbyte (w1, i);
+ unsigned char c2 = extractbyte (w2, i);
+ if (c1 == '\0' || c1 != c2)
+ return c1 - c2;
+ }
+ return 0;
+}
+
+/* Aligned loop: if a difference is found, exit to compare the bytes. Else
+ if a zero is found we have equal strings. */
+static inline int
+strcmp_aligned_loop (const op_t *x1, const op_t *x2, op_t w1)
+{
+ op_t w2 = *x2++;
+
+ while (w1 == w2)
+ {
+ if (has_zero (w1))
+ return 0;
+ w1 = *x1++;
+ w2 = *x2++;
+ }
+
+ return final_cmp (w1, w2);
+}
+
+/* Unaligned loop: align the first partial of P2, with 0xff for the rest of
+ the bytes so that we can also apply the has_zero test to see if we have
+ already reached EOS. If we have, then we can simply fall through to the
+ final comparison. */
+static inline int
+strcmp_unaligned_loop (const op_t *x1, const op_t *x2, op_t w1, uintptr_t ofs)
+{
+ op_t w2a = *x2++;
+ uintptr_t sh_1 = ofs * CHAR_BIT;
+ uintptr_t sh_2 = sizeof(op_t) * CHAR_BIT - sh_1;
+
+ op_t w2 = MERGE (w2a, sh_1, (op_t)-1, sh_2);
+ if (!has_zero (w2))
+ {
+ op_t w2b;
+
+ /* Unaligned loop. The invariant is that W2B, which is "ahead" of W1,
+ does not contain end-of-string. Therefore it is safe (and necessary)
+ to read another word from each while we do not have a difference. */
+ while (1)
+ {
+ w2b = *x2++;
+ w2 = MERGE (w2a, sh_1, w2b, sh_2);
+ if (w1 != w2)
+ return final_cmp (w1, w2);
+ if (has_zero (w2b))
+ break;
+ w1 = *x1++;
+ w2a = w2b;
+ }
+
+ /* Zero found in the second partial of P2. If we had EOS in the aligned
+ word, we have equality. */
+ if (has_zero (w1))
+ return 0;
+
+ /* Load the final word of P1 and align the final partial of P2. */
+ w1 = *x1++;
+ w2 = MERGE (w2b, sh_1, 0, sh_2);
+ }
+
+ return final_cmp (w1, w2);
+}
+
/* Compare S1 and S2, returning less than, equal to or
greater than zero if S1 is lexicographically less than,
equal to or greater than S2. */
int
-STRCMP (const char *p1, const char *p2)
+strcmp (const char *p1, const char *p2)
{
- const unsigned char *s1 = (const unsigned char *) p1;
- const unsigned char *s2 = (const unsigned char *) p2;
- unsigned char c1, c2;
-
- do
+ /* Handle the unaligned bytes of p1 first. */
+ uintptr_t n = -(uintptr_t)p1 % sizeof(op_t);
+ for (int i = 0; i < n; ++i)
{
- c1 = (unsigned char) *s1++;
- c2 = (unsigned char) *s2++;
- if (c1 == '\0')
- return c1 - c2;
+ unsigned char c1 = *p1++;
+ unsigned char c2 = *p2++;
+ int diff = c1 - c2;
+ if (c1 == '\0' || diff != 0)
+ return diff;
}
- while (c1 == c2);
- return c1 - c2;
+ /* P1 is now aligned to unsigned long. P2 may or may not be. */
+ const op_t *x1 = (const op_t *) p1;
+ op_t w1 = *x1++;
+ uintptr_t ofs = (uintptr_t) p2 % sizeof(op_t);
+ return ofs == 0
+ ? strcmp_aligned_loop (x1, (const op_t *)p2, w1)
+ : strcmp_unaligned_loop (x1, (const op_t *)(p2 - ofs), w1, ofs);
}
+#ifndef STRCMP
libc_hidden_builtin_def (strcmp)
+#endif
--
2.34.1
^ permalink raw reply [flat|nested] 26+ messages in thread
* [PATCH v6 10/17] string: Improve generic memchr
2023-01-10 21:00 [PATCH v6 00/17] Improve generic string routines Adhemerval Zanella
` (8 preceding siblings ...)
2023-01-10 21:00 ` [PATCH v6 09/17] string: Improve generic strcmp Adhemerval Zanella
@ 2023-01-10 21:00 ` Adhemerval Zanella
2023-01-10 21:01 ` [PATCH v6 11/17] string: Improve generic memrchr Adhemerval Zanella
` (6 subsequent siblings)
16 siblings, 0 replies; 26+ messages in thread
From: Adhemerval Zanella @ 2023-01-10 21:00 UTC (permalink / raw)
To: libc-alpha, Noah Goldstein, Richard Henderson; +Cc: Adhemerval Zanella Netto
From: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
New algorithm have the following key differences:
- Reads first word unaligned and use string-maskoff function to
remove unwanted data. This strategy follow arch-specific
optimization used on aarch64 and powerpc.
- Use string-fz{b,i} and string-opthr functions.
Checked on x86_64-linux-gnu, i686-linux-gnu, powerpc-linux-gnu,
and powerpc64-linux-gnu by removing the arch-specific assembly
implementation and disabling multi-arch (it covers both LE and BE
for 64 and 32 bits).
Co-authored-by: Richard Henderson <richard.henderson@linaro.org>
---
string/memchr.c | 171 +++++-------------
.../powerpc32/power4/multiarch/memchr-ppc32.c | 14 +-
.../powerpc64/multiarch/memchr-ppc64.c | 9 +-
3 files changed, 55 insertions(+), 139 deletions(-)
diff --git a/string/memchr.c b/string/memchr.c
index f800d47dce..90ef314372 100644
--- a/string/memchr.c
+++ b/string/memchr.c
@@ -1,10 +1,6 @@
-/* Copyright (C) 1991-2023 Free Software Foundation, Inc.
+/* Scan memory for a character. Generic version
+ Copyright (C) 1991-2023 Free Software Foundation, Inc.
This file is part of the GNU C Library.
- Based on strlen implementation by Torbjorn Granlund (tege@sics.se),
- with help from Dan Sahlin (dan@sics.se) and
- commentary by Jim Blandy (jimb@ai.mit.edu);
- adaptation to memchr suggested by Dick Karpinski (dick@cca.ucsf.edu),
- and implemented by Roland McGrath (roland@ai.mit.edu).
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
@@ -20,143 +16,76 @@
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
-#ifndef _LIBC
-# include <config.h>
-#endif
-
+#include <intprops.h>
+#include <string-fza.h>
+#include <string-fzb.h>
+#include <string-fzi.h>
+#include <string-maskoff.h>
+#include <string-opthr.h>
#include <string.h>
-#include <stddef.h>
-
-#include <limits.h>
+#undef memchr
-#undef __memchr
-#ifdef _LIBC
-# undef memchr
+#ifdef MEMCHR
+# define __memchr MEMCHR
#endif
-#ifndef weak_alias
-# define __memchr memchr
-#endif
-
-#ifndef MEMCHR
-# define MEMCHR __memchr
-#endif
+static inline const char *
+sadd (uintptr_t x, uintptr_t y)
+{
+ uintptr_t ret = INT_ADD_OVERFLOW (x, y) ? (uintptr_t)-1 : x + y;
+ return (const char *)ret;
+}
/* Search no more than N bytes of S for C. */
void *
-MEMCHR (void const *s, int c_in, size_t n)
+__memchr (void const *s, int c_in, size_t n)
{
- /* On 32-bit hardware, choosing longword to be a 32-bit unsigned
- long instead of a 64-bit uintmax_t tends to give better
- performance. On 64-bit hardware, unsigned long is generally 64
- bits already. Change this typedef to experiment with
- performance. */
- typedef unsigned long int longword;
-
- const unsigned char *char_ptr;
- const longword *longword_ptr;
- longword repeated_one;
- longword repeated_c;
- unsigned char c;
-
- c = (unsigned char) c_in;
+ if (__glibc_unlikely (n == 0))
+ return NULL;
- /* Handle the first few bytes by reading one byte at a time.
- Do this until CHAR_PTR is aligned on a longword boundary. */
- for (char_ptr = (const unsigned char *) s;
- n > 0 && (size_t) char_ptr % sizeof (longword) != 0;
- --n, ++char_ptr)
- if (*char_ptr == c)
- return (void *) char_ptr;
+ /* Read the first word, but munge it so that bytes before the array
+ will not match goal. */
+ const op_t *word_ptr = word_containing (s);
+ uintptr_t s_int = (uintptr_t) s;
- longword_ptr = (const longword *) char_ptr;
+ op_t word = *word_ptr;
+ op_t repeated_c = repeat_bytes (c_in);
+ op_t mask = check_mask (find_eq_all (word, repeated_c), s_int);
- /* All these elucidatory comments refer to 4-byte longwords,
- but the theory applies equally well to any size longwords. */
+ /* Compute the address of the last byte taking in consideration possible
+ overflow. */
+ const char *lbyte = sadd (s_int, n - 1);
+ /* And also the address of the word containing the last byte. */
+ const op_t *lword = word_containing (lbyte);
- /* Compute auxiliary longword values:
- repeated_one is a value which has a 1 in every byte.
- repeated_c has c in every byte. */
- repeated_one = 0x01010101;
- repeated_c = c | (c << 8);
- repeated_c |= repeated_c << 16;
- if (0xffffffffU < (longword) -1)
+ if (mask != 0)
{
- repeated_one |= repeated_one << 31 << 1;
- repeated_c |= repeated_c << 31 << 1;
- if (8 < sizeof (longword))
- {
- size_t i;
-
- for (i = 64; i < sizeof (longword) * 8; i *= 2)
- {
- repeated_one |= repeated_one << i;
- repeated_c |= repeated_c << i;
- }
- }
+ char *ret = (char *) s + index_first (mask);
+ return (ret <= lbyte) ? ret : NULL;
}
+ if (word_ptr == lword)
+ return NULL;
- /* Instead of the traditional loop which tests each byte, we will test a
- longword at a time. The tricky part is testing if *any of the four*
- bytes in the longword in question are equal to c. We first use an xor
- with repeated_c. This reduces the task to testing whether *any of the
- four* bytes in longword1 is zero.
-
- We compute tmp =
- ((longword1 - repeated_one) & ~longword1) & (repeated_one << 7).
- That is, we perform the following operations:
- 1. Subtract repeated_one.
- 2. & ~longword1.
- 3. & a mask consisting of 0x80 in every byte.
- Consider what happens in each byte:
- - If a byte of longword1 is zero, step 1 and 2 transform it into 0xff,
- and step 3 transforms it into 0x80. A carry can also be propagated
- to more significant bytes.
- - If a byte of longword1 is nonzero, let its lowest 1 bit be at
- position k (0 <= k <= 7); so the lowest k bits are 0. After step 1,
- the byte ends in a single bit of value 0 and k bits of value 1.
- After step 2, the result is just k bits of value 1: 2^k - 1. After
- step 3, the result is 0. And no carry is produced.
- So, if longword1 has only non-zero bytes, tmp is zero.
- Whereas if longword1 has a zero byte, call j the position of the least
- significant zero byte. Then the result has a zero at positions 0, ...,
- j-1 and a 0x80 at position j. We cannot predict the result at the more
- significant bytes (positions j+1..3), but it does not matter since we
- already have a non-zero bit at position 8*j+7.
-
- So, the test whether any byte in longword1 is zero is equivalent to
- testing whether tmp is nonzero. */
-
- while (n >= sizeof (longword))
+ word = *++word_ptr;
+ while (word_ptr != lword)
{
- longword longword1 = *longword_ptr ^ repeated_c;
-
- if ((((longword1 - repeated_one) & ~longword1)
- & (repeated_one << 7)) != 0)
- break;
- longword_ptr++;
- n -= sizeof (longword);
+ if (has_eq (word, repeated_c))
+ return (char *) word_ptr + index_first_eq (word, repeated_c);
+ word = *++word_ptr;
}
- char_ptr = (const unsigned char *) longword_ptr;
-
- /* At this point, we know that either n < sizeof (longword), or one of the
- sizeof (longword) bytes starting at char_ptr is == c. On little-endian
- machines, we could determine the first such byte without any further
- memory accesses, just by looking at the tmp result from the last loop
- iteration. But this does not work on big-endian machines. Choose code
- that works in both cases. */
-
- for (; n > 0; --n, ++char_ptr)
+ if (has_eq (word, repeated_c))
{
- if (*char_ptr == c)
- return (void *) char_ptr;
+ /* We found a match, but it might be in a byte past the end of the
+ array. */
+ char *ret = (char *) word_ptr + index_first_eq (word, repeated_c);
+ if (ret <= lbyte)
+ return ret;
}
-
return NULL;
}
-#ifdef weak_alias
+#ifndef MEMCHR
weak_alias (__memchr, memchr)
-#endif
libc_hidden_builtin_def (memchr)
+#endif
diff --git a/sysdeps/powerpc/powerpc32/power4/multiarch/memchr-ppc32.c b/sysdeps/powerpc/powerpc32/power4/multiarch/memchr-ppc32.c
index 39ff84f3f3..a78585650f 100644
--- a/sysdeps/powerpc/powerpc32/power4/multiarch/memchr-ppc32.c
+++ b/sysdeps/powerpc/powerpc32/power4/multiarch/memchr-ppc32.c
@@ -18,17 +18,11 @@
#include <string.h>
-#define MEMCHR __memchr_ppc
+extern __typeof (memchr) __memchr_ppc attribute_hidden;
-#undef weak_alias
-#define weak_alias(a, b)
+#define MEMCHR __memchr_ppc
+#include <string/memchr.c>
#ifdef SHARED
-# undef libc_hidden_builtin_def
-# define libc_hidden_builtin_def(name) \
- __hidden_ver1(__memchr_ppc, __GI_memchr, __memchr_ppc);
+__hidden_ver1(__memchr_ppc, __GI_memchr, __memchr_ppc);
#endif
-
-extern __typeof (memchr) __memchr_ppc attribute_hidden;
-
-#include <string/memchr.c>
diff --git a/sysdeps/powerpc/powerpc64/multiarch/memchr-ppc64.c b/sysdeps/powerpc/powerpc64/multiarch/memchr-ppc64.c
index 8097df709c..49ba5521fe 100644
--- a/sysdeps/powerpc/powerpc64/multiarch/memchr-ppc64.c
+++ b/sysdeps/powerpc/powerpc64/multiarch/memchr-ppc64.c
@@ -18,14 +18,7 @@
#include <string.h>
-#define MEMCHR __memchr_ppc
-
-#undef weak_alias
-#define weak_alias(a, b)
-
-# undef libc_hidden_builtin_def
-# define libc_hidden_builtin_def(name)
-
extern __typeof (memchr) __memchr_ppc attribute_hidden;
+#define MEMCHR __memchr_ppc
#include <string/memchr.c>
--
2.34.1
^ permalink raw reply [flat|nested] 26+ messages in thread
* [PATCH v6 11/17] string: Improve generic memrchr
2023-01-10 21:00 [PATCH v6 00/17] Improve generic string routines Adhemerval Zanella
` (9 preceding siblings ...)
2023-01-10 21:00 ` [PATCH v6 10/17] string: Improve generic memchr Adhemerval Zanella
@ 2023-01-10 21:01 ` Adhemerval Zanella
2023-01-10 21:01 ` [PATCH v6 12/17] hppa: Add memcopy.h Adhemerval Zanella
` (5 subsequent siblings)
16 siblings, 0 replies; 26+ messages in thread
From: Adhemerval Zanella @ 2023-01-10 21:01 UTC (permalink / raw)
To: libc-alpha, Noah Goldstein, Richard Henderson; +Cc: Adhemerval Zanella Netto
From: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
New algorithm have the following key differences:
- Use string-fz{b,i} functions.
Checked on x86_64-linux-gnu, i686-linux-gnu, powerpc-linux-gnu,
and powerpc64-linux-gnu by removing the arch-specific assembly
implementation and disabling multi-arch (it covers both LE and BE
for 64 and 32 bits).
Co-authored-by: Richard Henderson <richard.henderson@linaro.org>
---
string/memrchr.c | 189 ++++++++---------------------------------------
1 file changed, 32 insertions(+), 157 deletions(-)
diff --git a/string/memrchr.c b/string/memrchr.c
index 18b20ff76a..cc8cfda3ae 100644
--- a/string/memrchr.c
+++ b/string/memrchr.c
@@ -1,11 +1,6 @@
/* memrchr -- find the last occurrence of a byte in a memory block
Copyright (C) 1991-2023 Free Software Foundation, Inc.
This file is part of the GNU C Library.
- Based on strlen implementation by Torbjorn Granlund (tege@sics.se),
- with help from Dan Sahlin (dan@sics.se) and
- commentary by Jim Blandy (jimb@ai.mit.edu);
- adaptation to memchr suggested by Dick Karpinski (dick@cca.ucsf.edu),
- and implemented by Roland McGrath (roland@ai.mit.edu).
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
@@ -21,177 +16,57 @@
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
-#include <stdlib.h>
-
-#ifdef HAVE_CONFIG_H
-# include <config.h>
-#endif
-
-#if defined _LIBC
-# include <string.h>
-# include <memcopy.h>
-#endif
-
-#if defined HAVE_LIMITS_H || defined _LIBC
-# include <limits.h>
-#endif
-
-#define LONG_MAX_32_BITS 2147483647
-
-#ifndef LONG_MAX
-# define LONG_MAX LONG_MAX_32_BITS
-#endif
-
-#include <sys/types.h>
+#include <string-fzb.h>
+#include <string-fzi.h>
+#include <string-maskoff.h>
+#include <string-opthr.h>
+#include <string.h>
#undef __memrchr
#undef memrchr
-#ifndef weak_alias
-# define __memrchr memrchr
+#ifdef MEMRCHR
+# define __memrchr MEMRCHR
#endif
-/* Search no more than N bytes of S for C. */
void *
-#ifndef MEMRCHR
-__memrchr
-#else
-MEMRCHR
-#endif
- (const void *s, int c_in, size_t n)
+__memrchr (const void *s, int c_in, size_t n)
{
- const unsigned char *char_ptr;
- const unsigned long int *longword_ptr;
- unsigned long int longword, magic_bits, charmask;
- unsigned char c;
-
- c = (unsigned char) c_in;
-
/* Handle the last few characters by reading one character at a time.
- Do this until CHAR_PTR is aligned on a longword boundary. */
- for (char_ptr = (const unsigned char *) s + n;
- n > 0 && ((unsigned long int) char_ptr
- & (sizeof (longword) - 1)) != 0;
- --n)
- if (*--char_ptr == c)
+ Do this until CHAR_PTR is aligned on a word boundary, or
+ the entirety of small inputs. */
+ const unsigned char *char_ptr = (const unsigned char *) (s + n);
+ size_t align = (uintptr_t) char_ptr % sizeof (op_t);
+ if (n < OP_T_THRES || align > n)
+ align = n;
+ for (size_t i = 0; i < align; ++i)
+ if (*--char_ptr == c_in)
return (void *) char_ptr;
- /* All these elucidatory comments refer to 4-byte longwords,
- but the theory applies equally well to 8-byte longwords. */
+ const op_t *word_ptr = (const op_t *) char_ptr;
+ n -= align;
+ if (__glibc_unlikely (n == 0))
+ return NULL;
- longword_ptr = (const unsigned long int *) char_ptr;
+ /* Compute the address of the word containing the initial byte. */
+ const op_t *lword = word_containing (s);
- /* Bits 31, 24, 16, and 8 of this number are zero. Call these bits
- the "holes." Note that there is a hole just to the left of
- each byte, with an extra at the end:
-
- bits: 01111110 11111110 11111110 11111111
- bytes: AAAAAAAA BBBBBBBB CCCCCCCC DDDDDDDD
-
- The 1-bits make sure that carries propagate to the next 0-bit.
- The 0-bits provide holes for carries to fall into. */
- magic_bits = -1;
- magic_bits = magic_bits / 0xff * 0xfe << 1 >> 1 | 1;
-
- /* Set up a longword, each of whose bytes is C. */
- charmask = c | (c << 8);
- charmask |= charmask << 16;
-#if LONG_MAX > LONG_MAX_32_BITS
- charmask |= charmask << 32;
-#endif
+ /* Set up a word, each of whose bytes is C. */
+ op_t repeated_c = repeat_bytes (c_in);
- /* Instead of the traditional loop which tests each character,
- we will test a longword at a time. The tricky part is testing
- if *any of the four* bytes in the longword in question are zero. */
- while (n >= sizeof (longword))
+ while (word_ptr != lword)
{
- /* We tentatively exit the loop if adding MAGIC_BITS to
- LONGWORD fails to change any of the hole bits of LONGWORD.
-
- 1) Is this safe? Will it catch all the zero bytes?
- Suppose there is a byte with all zeros. Any carry bits
- propagating from its left will fall into the hole at its
- least significant bit and stop. Since there will be no
- carry from its most significant bit, the LSB of the
- byte to the left will be unchanged, and the zero will be
- detected.
-
- 2) Is this worthwhile? Will it ignore everything except
- zero bytes? Suppose every byte of LONGWORD has a bit set
- somewhere. There will be a carry into bit 8. If bit 8
- is set, this will carry into bit 16. If bit 8 is clear,
- one of bits 9-15 must be set, so there will be a carry
- into bit 16. Similarly, there will be a carry into bit
- 24. If one of bits 24-30 is set, there will be a carry
- into bit 31, so all of the hole bits will be changed.
-
- The one misfire occurs when bits 24-30 are clear and bit
- 31 is set; in this case, the hole at bit 31 is not
- changed. If we had access to the processor carry flag,
- we could close this loophole by putting the fourth hole
- at bit 32!
-
- So it ignores everything except 128's, when they're aligned
- properly.
-
- 3) But wait! Aren't we looking for C, not zero?
- Good point. So what we do is XOR LONGWORD with a longword,
- each of whose bytes is C. This turns each byte that is C
- into a zero. */
-
- longword = *--longword_ptr ^ charmask;
-
- /* Add MAGIC_BITS to LONGWORD. */
- if ((((longword + magic_bits)
-
- /* Set those bits that were unchanged by the addition. */
- ^ ~longword)
-
- /* Look at only the hole bits. If any of the hole bits
- are unchanged, most likely one of the bytes was a
- zero. */
- & ~magic_bits) != 0)
+ op_t word = *--word_ptr;
+ if (has_eq (word, repeated_c))
{
- /* Which of the bytes was C? If none of them were, it was
- a misfire; continue the search. */
-
- const unsigned char *cp = (const unsigned char *) longword_ptr;
-
-#if LONG_MAX > 2147483647
- if (cp[7] == c)
- return (void *) &cp[7];
- if (cp[6] == c)
- return (void *) &cp[6];
- if (cp[5] == c)
- return (void *) &cp[5];
- if (cp[4] == c)
- return (void *) &cp[4];
-#endif
- if (cp[3] == c)
- return (void *) &cp[3];
- if (cp[2] == c)
- return (void *) &cp[2];
- if (cp[1] == c)
- return (void *) &cp[1];
- if (cp[0] == c)
- return (void *) cp;
+ /* We found a match, but it might be in a byte past the start
+ of the array. */
+ char *ret = (char *) word_ptr + index_last_eq (word, repeated_c);
+ return ret >= (char *) s ? ret : NULL;
}
-
- n -= sizeof (longword);
}
-
- char_ptr = (const unsigned char *) longword_ptr;
-
- while (n-- > 0)
- {
- if (*--char_ptr == c)
- return (void *) char_ptr;
- }
-
- return 0;
+ return NULL;
}
#ifndef MEMRCHR
-# ifdef weak_alias
weak_alias (__memrchr, memrchr)
-# endif
#endif
--
2.34.1
^ permalink raw reply [flat|nested] 26+ messages in thread
* [PATCH v6 12/17] hppa: Add memcopy.h
2023-01-10 21:00 [PATCH v6 00/17] Improve generic string routines Adhemerval Zanella
` (10 preceding siblings ...)
2023-01-10 21:01 ` [PATCH v6 11/17] string: Improve generic memrchr Adhemerval Zanella
@ 2023-01-10 21:01 ` Adhemerval Zanella
2023-01-10 21:01 ` [PATCH v6 13/17] hppa: Add string-fzb.h and string-fzi.h Adhemerval Zanella
` (4 subsequent siblings)
16 siblings, 0 replies; 26+ messages in thread
From: Adhemerval Zanella @ 2023-01-10 21:01 UTC (permalink / raw)
To: libc-alpha, Noah Goldstein, Richard Henderson
From: Richard Henderson <richard.henderson@linaro.org>
GCC's combine pass cannot merge (x >> c | y << (32 - c)) into a
double-word shift unless (1) the subtract is in the same basic block
and (2) the result of the subtract is used exactly once. Neither
condition is true for any use of MERGE.
By forcing the use of a double-word shift, we not only reduce
contention on SAR, but also allow the setting of SAR to be hoisted
outside of a loop.
Checked on hppa-linux-gnu.
---
sysdeps/hppa/memcopy.h | 42 ++++++++++++++++++++++++++++++++++++++++++
1 file changed, 42 insertions(+)
create mode 100644 sysdeps/hppa/memcopy.h
diff --git a/sysdeps/hppa/memcopy.h b/sysdeps/hppa/memcopy.h
new file mode 100644
index 0000000000..0d4b4ac435
--- /dev/null
+++ b/sysdeps/hppa/memcopy.h
@@ -0,0 +1,42 @@
+/* Definitions for memory copy functions, PA-RISC version.
+ Copyright (C) 2023 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library. If not, see
+ <http://www.gnu.org/licenses/>. */
+
+#include <sysdeps/generic/memcopy.h>
+
+/* Use a single double-word shift instead of two shifts and an ior.
+ If the uses of MERGE were close to the computation of shl/shr,
+ the compiler might have been able to create this itself.
+ But instead that computation is well separated.
+
+ Using an inline function instead of a macro is the easiest way
+ to ensure that the types are correct. */
+
+#undef MERGE
+
+static __always_inline op_t
+MERGE (op_t w0, int shl, op_t w1, int shr)
+{
+ _Static_assert (OPSIZ == 4 || OPSIZ == 8, "Invalid OPSIZE");
+
+ op_t res;
+ if (OPSIZ == 4)
+ asm ("shrpw %1,%2,%%sar,%0" : "=r"(res) : "r"(w0), "r"(w1), "q"(shr));
+ else if (OPSIZ == 8)
+ asm ("shrpd %1,%2,%%sar,%0" : "=r"(res) : "r"(w0), "r"(w1), "q"(shr));
+ return res;
+}
--
2.34.1
^ permalink raw reply [flat|nested] 26+ messages in thread
* [PATCH v6 13/17] hppa: Add string-fzb.h and string-fzi.h
2023-01-10 21:00 [PATCH v6 00/17] Improve generic string routines Adhemerval Zanella
` (11 preceding siblings ...)
2023-01-10 21:01 ` [PATCH v6 12/17] hppa: Add memcopy.h Adhemerval Zanella
@ 2023-01-10 21:01 ` Adhemerval Zanella
2023-01-10 21:01 ` [PATCH v6 14/17] alpha: " Adhemerval Zanella
` (3 subsequent siblings)
16 siblings, 0 replies; 26+ messages in thread
From: Adhemerval Zanella @ 2023-01-10 21:01 UTC (permalink / raw)
To: libc-alpha, Noah Goldstein, Richard Henderson
From: Richard Henderson <richard.henderson@linaro.org>
Use UXOR,SBZ to test for a zero byte within a word. While we can
get semi-decent code out of asm-goto, we would do slightly better
with a compiler builtin.
For index_zero et al, sequential testing of bytes is less expensive than
any tricks that involve a count-leading-zeros insn that we don't have.
Checked on hppa-linux-gnu.
---
sysdeps/hppa/string-fzb.h | 70 +++++++++++++++++++
sysdeps/hppa/string-fzi.h | 139 ++++++++++++++++++++++++++++++++++++++
2 files changed, 209 insertions(+)
create mode 100644 sysdeps/hppa/string-fzb.h
create mode 100644 sysdeps/hppa/string-fzi.h
diff --git a/sysdeps/hppa/string-fzb.h b/sysdeps/hppa/string-fzb.h
new file mode 100644
index 0000000000..865e548492
--- /dev/null
+++ b/sysdeps/hppa/string-fzb.h
@@ -0,0 +1,70 @@
+/* Zero byte detection, boolean. HPPA version.
+ Copyright (C) 2023 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#ifndef _STRING_FZB_H
+#define _STRING_FZB_H 1
+
+#include <sys/cdefs.h>
+#include <string-optype.h>
+
+/* Determine if any byte within X is zero. This is a pure boolean test. */
+
+static __always_inline _Bool
+has_zero (op_t x)
+{
+ _Static_assert (sizeof (op_t) == 4, "64-bit not supported");
+
+ /* It's more useful to expose a control transfer to the compiler
+ than to expose a proper boolean result. */
+ asm goto ("uxor,sbz %%r0,%0,%%r0\n\t"
+ "b,n %l1" : : "r"(x) : : nbz);
+ return 1;
+ nbz:
+ return 0;
+}
+
+/* Likewise, but for byte equality between X1 and X2. */
+
+static __always_inline _Bool
+has_eq (op_t x1, op_t x2)
+{
+ _Static_assert (sizeof (op_t) == 4, "64-bit not supported");
+
+ asm goto ("uxor,sbz %0,%1,%%r0\n\t"
+ "b,n %l2" : : "r"(x1), "r"(x2) : : nbz);
+ return 1;
+ nbz:
+ return 0;
+}
+
+/* Likewise, but for zeros in X1 and equal bytes between X1 and X2. */
+
+static __always_inline _Bool
+has_zero_eq (op_t x1, op_t x2)
+{
+ _Static_assert (sizeof (op_t) == 4, "64-bit not supported");
+
+ asm goto ("uxor,sbz %%r0,%0,%%r0\n\t"
+ "uxor,nbz %0,%1,%%r0\n\t"
+ "b,n %l2" : : "r"(x1), "r"(x2) : : sbz);
+ return 0;
+ sbz:
+ return 1;
+}
+
+#endif /* _STRING_FZB_H */
diff --git a/sysdeps/hppa/string-fzi.h b/sysdeps/hppa/string-fzi.h
new file mode 100644
index 0000000000..1824cbba5a
--- /dev/null
+++ b/sysdeps/hppa/string-fzi.h
@@ -0,0 +1,139 @@
+/* string-fzi.h -- zero byte detection; indexes. HPPA version.
+ Copyright (C) 2022 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#ifndef _STRING_FZI_H
+#define _STRING_FZI_H 1
+
+#include <limits.h>
+#include <string-optype.h>
+
+_Static_assert (sizeof (op_t) == 4, "64-bit not supported");
+
+static __always_inline unsigned int
+index_first (op_t c)
+{
+ /* Since we have no clz insn, direct tests of the bytes is faster
+ than loading up the constants to do the masking. */
+ if (c & 0xff000000)
+ return 0;
+ if (c & 0x00ff0000)
+ return 1;
+ if (c & 0x0000ff00)
+ return 2;
+ return 3;
+}
+
+/* Given a word X that is known to contain a zero byte, return the
+ index of the first such within the long in memory order. */
+static __always_inline unsigned int
+index_first_zero (op_t x)
+{
+ unsigned int ret;
+
+ /* Since we have no clz insn, direct tests of the bytes is faster
+ than loading up the constants to do the masking. */
+ asm ("extrw,u,<> %1,23,8,%%r0\n\t"
+ "ldi 2,%0\n\t"
+ "extrw,u,<> %1,15,8,%%r0\n\t"
+ "ldi 1,%0\n\t"
+ "extrw,u,<> %1,7,8,%%r0\n\t"
+ "ldi 0,%0"
+ : "=r"(ret) : "r"(x), "0"(3));
+
+ return ret;
+}
+
+/* Similarly, but perform the search for byte equality between X1 and X2. */
+static __always_inline unsigned int
+index_first_eq (op_t x1, op_t x2)
+{
+ return index_first_zero (x1 ^ x2);
+}
+
+/* Similarly, but perform the search for zero within X1 or
+ equality between X1 and X2. */
+static __always_inline unsigned int
+index_first_zero_eq (op_t x1, op_t x2)
+{
+ unsigned int ret;
+
+ /* Since we have no clz insn, direct tests of the bytes is faster
+ than loading up the constants to do the masking. */
+ asm ("extrw,u,= %1,23,8,%%r0\n\t"
+ "extrw,u,<> %2,23,8,%%r0\n\t"
+ "ldi 2,%0\n\t"
+ "extrw,u,= %1,15,8,%%r0\n\t"
+ "extrw,u,<> %2,15,8,%%r0\n\t"
+ "ldi 1,%0\n\t"
+ "extrw,u,= %1,7,8,%%r0\n\t"
+ "extrw,u,<> %2,7,8,%%r0\n\t"
+ "ldi 0,%0"
+ : "=r"(ret) : "r"(x1), "r"(x1 ^ x2), "0"(3));
+
+ return ret;
+}
+
+/* Similarly, but perform the search for zero within X1 or
+ inequality between X1 and X2. */
+static __always_inline unsigned int
+index_first_zero_ne (op_t x1, op_t x2)
+{
+ unsigned int ret;
+
+ /* Since we have no clz insn, direct tests of the bytes is faster
+ than loading up the constants to do the masking. */
+ asm ("extrw,u,<> %2,23,8,%%r0\n\t"
+ "extrw,u,<> %1,23,8,%%r0\n\t"
+ "ldi 2,%0\n\t"
+ "extrw,u,<> %2,15,8,%%r0\n\t"
+ "extrw,u,<> %1,15,8,%%r0\n\t"
+ "ldi 1,%0\n\t"
+ "extrw,u,<> %2,7,8,%%r0\n\t"
+ "extrw,u,<> %1,7,8,%%r0\n\t"
+ "ldi 0,%0"
+ : "=r"(ret) : "r"(x1), "r"(x1 ^ x2), "0"(3));
+
+ return ret;
+}
+
+/* Similarly, but search for the last zero within X. */
+static __always_inline unsigned int
+index_last_zero (op_t x)
+{
+ unsigned int ret;
+
+ /* Since we have no ctz insn, direct tests of the bytes is faster
+ than loading up the constants to do the masking. */
+ asm ("extrw,u,<> %1,15,8,%%r0\n\t"
+ "ldi 1,%0\n\t"
+ "extrw,u,<> %1,23,8,%%r0\n\t"
+ "ldi 2,%0\n\t"
+ "extrw,u,<> %1,31,8,%%r0\n\t"
+ "ldi 3,%0"
+ : "=r"(ret) : "r"(x), "0"(0));
+
+ return ret;
+}
+
+static __always_inline unsigned int
+index_last_eq (op_t x1, op_t x2)
+{
+ return index_last_zero (x1 ^ x2);
+}
+
+#endif /* _STRING_FZI_H */
--
2.34.1
^ permalink raw reply [flat|nested] 26+ messages in thread
* [PATCH v6 14/17] alpha: Add string-fzb.h and string-fzi.h
2023-01-10 21:00 [PATCH v6 00/17] Improve generic string routines Adhemerval Zanella
` (12 preceding siblings ...)
2023-01-10 21:01 ` [PATCH v6 13/17] hppa: Add string-fzb.h and string-fzi.h Adhemerval Zanella
@ 2023-01-10 21:01 ` Adhemerval Zanella
2023-01-11 2:45 ` Richard Henderson
2023-01-10 21:01 ` [PATCH v6 15/17] arm: Add string-fza.h Adhemerval Zanella
` (2 subsequent siblings)
16 siblings, 1 reply; 26+ messages in thread
From: Adhemerval Zanella @ 2023-01-10 21:01 UTC (permalink / raw)
To: libc-alpha, Noah Goldstein, Richard Henderson
From: Richard Henderson <richard.henderson@linaro.org>
While alpha has the more important string functions in assembly,
there are still a few for find the generic routines are used.
Use the CMPBGE insn, via the builtin, for testing of zeros. Use a
simplified expansion of __builtin_ctz when the insn isn't available.
Checked on alpha-linux-gnu.
---
sysdeps/alpha/string-fzb.h | 52 +++++++++++++++++
sysdeps/alpha/string-fzi.h | 113 +++++++++++++++++++++++++++++++++++++
2 files changed, 165 insertions(+)
create mode 100644 sysdeps/alpha/string-fzb.h
create mode 100644 sysdeps/alpha/string-fzi.h
diff --git a/sysdeps/alpha/string-fzb.h b/sysdeps/alpha/string-fzb.h
new file mode 100644
index 0000000000..e3934ba413
--- /dev/null
+++ b/sysdeps/alpha/string-fzb.h
@@ -0,0 +1,52 @@
+/* Zero byte detection; boolean. Alpha version.
+ Copyright (C) 2023 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#ifndef _STRING_FZB_H
+#define _STRING_FZB_H 1
+
+#include <sys/cdefs.h>
+#include <string-optype.h>
+
+/* Note that since CMPBGE creates a bit mask rather than a byte mask,
+ we cannot simply provide a target-specific string-fza.h. */
+
+/* Determine if any byte within X is zero. This is a pure boolean test. */
+
+static __always_inline _Bool
+has_zero (op_t x)
+{
+ return __builtin_alpha_cmpbge (0, x) != 0;
+}
+
+/* Likewise, but for byte equality between X1 and X2. */
+
+static __always_inline _Bool
+has_eq (op_t x1, op_t x2)
+{
+ return has_zero (x1 ^ x2);
+}
+
+/* Likewise, but for zeros in X1 and equal bytes between X1 and X2. */
+
+static __always_inline _Bool
+has_zero_eq (op_t x1, op_t x2)
+{
+ return has_zero (x1) | has_eq (x1, x2);
+}
+
+#endif /* _STRING_FZB_H */
diff --git a/sysdeps/alpha/string-fzi.h b/sysdeps/alpha/string-fzi.h
new file mode 100644
index 0000000000..bc2f0bdc91
--- /dev/null
+++ b/sysdeps/alpha/string-fzi.h
@@ -0,0 +1,113 @@
+/* string-fzi.h -- zero byte detection; indices. Alpha version.
+ Copyright (C) 2022 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#ifndef _STRING_FZI_H
+#define _STRING_FZI_H
+
+#include <limits.h>
+#include <string-optype.h>
+
+/* Note that since CMPBGE creates a bit mask rather than a byte mask,
+ we cannot simply provide a target-specific string-fza.h. */
+
+/* A subroutine for the index_zero functions. Given a bitmask C,
+ return the index of the first bit set in memory order. */
+
+static __always_inline unsigned int
+index_first (unsigned long int c)
+{
+#ifdef __alpha_cix__
+ return __builtin_ctzl (c);
+#else
+ c = c & -c;
+ return (c & 0xf0 ? 4 : 0) + (c & 0xcc ? 2 : 0) + (c & 0xaa ? 1 : 0);
+#endif
+}
+
+/* Similarly, but return the (memory order) index of the last bit
+ that is non-zero. Note that only the least 8 bits may be nonzero. */
+
+static __always_inline unsigned int
+index_last (unsigned long int x)
+{
+#ifdef __alpha_cix__
+ return __builtin_clzl (x) ^ 63;
+#else
+ unsigned r = 0;
+ if (x & 0xf0)
+ r += 4;
+ if (x & (0xc << r))
+ r += 2;
+ if (x & (0x2 << r))
+ r += 1;
+ return r;
+#endif
+}
+
+/* Given a word X that is known to contain a zero byte, return the
+ index of the first such within the word in memory order. */
+
+static __always_inline unsigned int
+index_first_zero (op_t x)
+{
+ return index_first (__builtin_alpha_cmpbge (0, x));
+}
+
+/* Similarly, but perform the test for byte equality between X1 and X2. */
+
+static __always_inline unsigned int
+index_first_eq (op_t x1, op_t x2)
+{
+ return index_first_zero (x1 ^ x2);
+}
+
+/* Similarly, but perform the search for zero within X1 or
+ equality between X1 and X2. */
+
+static __always_inline unsigned int
+index_first_zero_eq (op_t x1, op_t x2)
+{
+ return index_first (__builtin_alpha_cmpbge (0, x1)
+ | __builtin_alpha_cmpbge (0, x1 ^ x2));
+}
+
+/* Similarly, but perform the search for zero within X1 or
+ inequality between X1 and X2. */
+
+static __always_inline unsigned int
+index_first_zero_ne (op_t x1, op_t x2)
+{
+ return index_first (__builtin_alpha_cmpbge (0, x1)
+ | (__builtin_alpha_cmpbge (0, x1 ^ x2) ^ 0xFF));
+}
+
+/* Similarly, but search for the last zero within X. */
+
+static __always_inline unsigned int
+index_last_zero (op_t x)
+{
+ return index_last (__builtin_alpha_cmpbge (0, x));
+}
+
+static __always_inline unsigned int
+index_last_eq (op_t x1, op_t x2)
+{
+ return index_last_zero (x1 ^ x2);
+}
+
+#endif /* _STRING_FZI_H */
--
2.34.1
^ permalink raw reply [flat|nested] 26+ messages in thread
* [PATCH v6 15/17] arm: Add string-fza.h
2023-01-10 21:00 [PATCH v6 00/17] Improve generic string routines Adhemerval Zanella
` (13 preceding siblings ...)
2023-01-10 21:01 ` [PATCH v6 14/17] alpha: " Adhemerval Zanella
@ 2023-01-10 21:01 ` Adhemerval Zanella
2023-01-10 21:01 ` [PATCH v6 16/17] powerpc: " Adhemerval Zanella
2023-01-10 21:01 ` [PATCH v6 17/17] sh: Add string-fzb.h Adhemerval Zanella
16 siblings, 0 replies; 26+ messages in thread
From: Adhemerval Zanella @ 2023-01-10 21:01 UTC (permalink / raw)
To: libc-alpha, Noah Goldstein, Richard Henderson
From: Richard Henderson <richard.henderson@linaro.org>
While arm has the more important string functions in assembly,
there are still a few generic routines used.
Use the UQSUB8 insn for testing of zeros.
Checked on armv7-linux-gnueabihf
---
sysdeps/arm/armv6t2/string-fza.h | 70 ++++++++++++++++++++++++++++++++
1 file changed, 70 insertions(+)
create mode 100644 sysdeps/arm/armv6t2/string-fza.h
diff --git a/sysdeps/arm/armv6t2/string-fza.h b/sysdeps/arm/armv6t2/string-fza.h
new file mode 100644
index 0000000000..7aa0843325
--- /dev/null
+++ b/sysdeps/arm/armv6t2/string-fza.h
@@ -0,0 +1,70 @@
+/* Zero byte detection; basics. ARM version.
+ Copyright (C) 2023 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#ifndef _STRING_FZA_H
+#define _STRING_FZA_H 1
+
+#include <string-optype.h>
+#include <string-maskoff.h>
+
+/* This function returns at least one bit set within every byte
+ of X that is zero. */
+
+static __always_inline op_t
+find_zero_all (op_t x)
+{
+ /* Use unsigned saturated subtraction from 1 in each byte.
+ That leaves 1 for every byte that was zero. */
+ op_t ret, ones = repeat_bytes (0x01);
+ asm ("uqsub8 %0,%1,%2" : "=r"(ret) : "r"(ones), "r"(x));
+ return ret;
+}
+
+/* Identify bytes that are equal between X1 and X2. */
+
+static __always_inline op_t
+find_eq_all (op_t x1, op_t x2)
+{
+ return find_zero_all (x1 ^ x2);
+}
+
+/* Identify zero bytes in X1 or equality between X1 and X2. */
+
+static __always_inline op_t
+find_zero_eq_all (op_t x1, op_t x2)
+{
+ return find_zero_all (x1) | find_zero_all (x1 ^ x2);
+}
+
+/* Identify zero bytes in X1 or inequality between X1 and X2. */
+
+static __always_inline op_t
+find_zero_ne_all (op_t x1, op_t x2)
+{
+ /* Make use of the fact that we'll already have ONES in a register. */
+ op_t ones = repeat_bytes (0x01);
+ return find_zero_all (x1) | (find_zero_all (x1 ^ x2) ^ ones);
+}
+
+/* Define the "inexact" versions in terms of the exact versions. */
+#define find_zero_low find_zero_all
+#define find_eq_low find_eq_all
+#define find_zero_eq_low find_zero_eq_all
+#define find_zero_ne_low find_zero_ne_all
+
+#endif /* _STRING_FZA_H */
--
2.34.1
^ permalink raw reply [flat|nested] 26+ messages in thread
* [PATCH v6 16/17] powerpc: Add string-fza.h
2023-01-10 21:00 [PATCH v6 00/17] Improve generic string routines Adhemerval Zanella
` (14 preceding siblings ...)
2023-01-10 21:01 ` [PATCH v6 15/17] arm: Add string-fza.h Adhemerval Zanella
@ 2023-01-10 21:01 ` Adhemerval Zanella
2023-01-11 1:18 ` Carlos Seo
2023-01-10 21:01 ` [PATCH v6 17/17] sh: Add string-fzb.h Adhemerval Zanella
16 siblings, 1 reply; 26+ messages in thread
From: Adhemerval Zanella @ 2023-01-10 21:01 UTC (permalink / raw)
To: libc-alpha, Noah Goldstein, Richard Henderson
From: Richard Henderson <richard.henderson@linaro.org>
While ppc has the more important string functions in assembly,
there are still a few generic routines used.
Use the Power 6 CMPB insn for testing of zeros.
Checked on powerpc64le-linux-gnu.
---
sysdeps/powerpc/string-fza.h | 70 ++++++++++++++++++++++++++++++++++++
1 file changed, 70 insertions(+)
create mode 100644 sysdeps/powerpc/string-fza.h
diff --git a/sysdeps/powerpc/string-fza.h b/sysdeps/powerpc/string-fza.h
new file mode 100644
index 0000000000..5496c9db4b
--- /dev/null
+++ b/sysdeps/powerpc/string-fza.h
@@ -0,0 +1,70 @@
+/* Zero byte detection; basics. PowerPC version.
+ Copyright (C) 2023 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#ifndef _POWERPC_STRING_FZA_H
+#define _POWERPC_STRING_FZA_H 1
+
+/* PowerISA 2.05 (POWER6) provides cmpb instruction. */
+#ifdef _ARCH_PWR6
+# include <string-optype.h>
+
+/* This function returns 0xff for each byte that is
+ equal between X1 and X2. */
+
+static __always_inline op_t
+find_eq_all (op_t x1, op_t x2)
+{
+ op_t ret;
+ asm ("cmpb %0,%1,%2" : "=r"(ret) : "r"(x1), "r"(x2));
+ return ret;
+}
+
+/* This function returns 0xff for each byte that is zero in X. */
+
+static __always_inline op_t
+find_zero_all (op_t x)
+{
+ return find_eq_all (x, 0);
+}
+
+/* Identify zero bytes in X1 or equality between X1 and X2. */
+
+static __always_inline op_t
+find_zero_eq_all (op_t x1, op_t x2)
+{
+ return find_zero_all (x1) | find_eq_all (x1, x2);
+}
+
+/* Identify zero bytes in X1 or inequality between X1 and X2. */
+
+static __always_inline op_t
+find_zero_ne_all (op_t x1, op_t x2)
+{
+ return find_zero_all (x1) | ~find_eq_all (x1, x2);
+}
+
+/* Define the "inexact" versions in terms of the exact versions. */
+# define find_zero_low find_zero_all
+# define find_eq_low find_eq_all
+# define find_zero_eq_low find_zero_eq_all
+# define find_zero_ne_low find_zero_ne_all
+#else
+# include <sysdeps/generic/string-fza.h>
+#endif /* _ARCH_PWR6 */
+
+#endif /* _POWERPC_STRING_FZA_H */
--
2.34.1
^ permalink raw reply [flat|nested] 26+ messages in thread
* [PATCH v6 17/17] sh: Add string-fzb.h
2023-01-10 21:00 [PATCH v6 00/17] Improve generic string routines Adhemerval Zanella
` (15 preceding siblings ...)
2023-01-10 21:01 ` [PATCH v6 16/17] powerpc: " Adhemerval Zanella
@ 2023-01-10 21:01 ` Adhemerval Zanella
16 siblings, 0 replies; 26+ messages in thread
From: Adhemerval Zanella @ 2023-01-10 21:01 UTC (permalink / raw)
To: libc-alpha, Noah Goldstein, Richard Henderson; +Cc: Adhemerval Zanella Netto
From: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
Use the SH cmp/str on has_{zero,eq,zero_eq}.
Checked on sh4-linux-gnu.
---
sysdeps/sh/string-fzb.h | 54 +++++++++++++++++++++++++++++++++++++++++
1 file changed, 54 insertions(+)
create mode 100644 sysdeps/sh/string-fzb.h
diff --git a/sysdeps/sh/string-fzb.h b/sysdeps/sh/string-fzb.h
new file mode 100644
index 0000000000..0ad19b58c9
--- /dev/null
+++ b/sysdeps/sh/string-fzb.h
@@ -0,0 +1,54 @@
+/* Zero byte detection; boolean. SH4 version.
+ Copyright (C) 2023 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#ifndef STRING_FZB_H
+#define STRING_FZB_H 1
+
+#include <sys/cdefs.h>
+#include <string-optype.h>
+
+/* Determine if any byte within X is zero. This is a pure boolean test. */
+
+static __always_inline _Bool
+has_zero (op_t x)
+{
+ op_t zero = 0x0, ret;
+ asm volatile ("cmp/str %1,%2\n"
+ "movt %0\n"
+ : "=r" (ret)
+ : "r" (zero), "r" (x));
+ return ret;
+}
+
+/* Likewise, but for byte equality between X1 and X2. */
+
+static __always_inline _Bool
+has_eq (op_t x1, op_t x2)
+{
+ return has_zero (x1 ^ x2);
+}
+
+/* Likewise, but for zeros in X1 and equal bytes between X1 and X2. */
+
+static __always_inline _Bool
+has_zero_eq (op_t x1, op_t x2)
+{
+ return has_zero (x1) | has_eq (x1, x2);
+}
+
+#endif /* STRING_FZB_H */
--
2.34.1
^ permalink raw reply [flat|nested] 26+ messages in thread
* Re: [PATCH v6 16/17] powerpc: Add string-fza.h
2023-01-10 21:01 ` [PATCH v6 16/17] powerpc: " Adhemerval Zanella
@ 2023-01-11 1:18 ` Carlos Seo
0 siblings, 0 replies; 26+ messages in thread
From: Carlos Seo @ 2023-01-11 1:18 UTC (permalink / raw)
To: Adhemerval Zanella; +Cc: libc-alpha, Noah Goldstein, Richard Henderson
On Tue, 10 Jan 2023 at 18:04, Adhemerval Zanella via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> From: Richard Henderson <richard.henderson@linaro.org>
>
> While ppc has the more important string functions in assembly,
> there are still a few generic routines used.
>
> Use the Power 6 CMPB insn for testing of zeros.
>
> Checked on powerpc64le-linux-gnu.
> ---
LGTM.
^ permalink raw reply [flat|nested] 26+ messages in thread
* Re: [PATCH v6 03/17] Add string-maskoff.h generic header
2023-01-10 21:00 ` [PATCH v6 03/17] Add string-maskoff.h generic header Adhemerval Zanella
@ 2023-01-11 1:58 ` Richard Henderson
2023-01-11 13:39 ` Adhemerval Zanella Netto
0 siblings, 1 reply; 26+ messages in thread
From: Richard Henderson @ 2023-01-11 1:58 UTC (permalink / raw)
To: Adhemerval Zanella, libc-alpha, Noah Goldstein
On 1/10/23 13:00, Adhemerval Zanella wrote:
> +/* Return the address of the op_t word containing the address P. For
> + instance on address 0x0011223344556677 and op_t with size of 8,
> + it returns 0x0011223344556670. */
> +static __always_inline op_t *
> +word_containing (char const *p)
> +{
> + return (op_t *) ((uintptr_t) p & -sizeof(p));
> +}
sizeof(op_t).
r~
^ permalink raw reply [flat|nested] 26+ messages in thread
* Re: [PATCH v6 04/17] Add string vectorized find and detection functions
2023-01-10 21:00 ` [PATCH v6 04/17] Add string vectorized find and detection functions Adhemerval Zanella
@ 2023-01-11 2:25 ` Richard Henderson
2023-01-11 13:42 ` Adhemerval Zanella Netto
0 siblings, 1 reply; 26+ messages in thread
From: Richard Henderson @ 2023-01-11 2:25 UTC (permalink / raw)
To: Adhemerval Zanella, libc-alpha, Noah Goldstein
On 1/10/23 13:00, Adhemerval Zanella wrote:
> --- a/sysdeps/generic/string-maskoff.h
> +++ b/sysdeps/generic/string-maskoff.h
> @@ -23,7 +23,6 @@
> #include <limits.h>
> #include <stdint.h>
> #include <string-optype.h>
> -#include <string-fza.h>
>
> /* Provide a mask based on the pointer alignment that sets up non-zero
> bytes before the beginning of the word. It is used to mask off
> @@ -44,12 +43,12 @@ create_mask (uintptr_t i)
> /* Return the mask WORD shifted based on S_INT address value, to ignore
> values not presented in the aligned word read. */
> static __always_inline op_t
> -check_mask (op_t word, uintptr_t s_int)
> +check_mask (op_t word, uintptr_t s)
> {
> if (__BYTE_ORDER == __LITTLE_ENDIAN)
> - return word >> (CHAR_BIT * (s_int % sizeof (s_int)));
> + return word >> (CHAR_BIT * (s % sizeof (op_t)));
> else
> - return word << (CHAR_BIT * (s_int % sizeof (s_int)));
> + return word << (CHAR_BIT * (s % sizeof (op_t)));
> }
Fold this into patch 3, if you want it.
> @@ -79,7 +78,7 @@ highbit_mask (op_t m)
> static __always_inline op_t *
> word_containing (char const *p)
> {
> - return (op_t *) ((uintptr_t) p & -sizeof(p));
> + return (op_t *) ((op_t) p & -sizeof(p));
Casting p to op_t is wrong.
r~
^ permalink raw reply [flat|nested] 26+ messages in thread
* Re: [PATCH v6 14/17] alpha: Add string-fzb.h and string-fzi.h
2023-01-10 21:01 ` [PATCH v6 14/17] alpha: " Adhemerval Zanella
@ 2023-01-11 2:45 ` Richard Henderson
2023-01-11 17:27 ` Adhemerval Zanella Netto
0 siblings, 1 reply; 26+ messages in thread
From: Richard Henderson @ 2023-01-11 2:45 UTC (permalink / raw)
To: Adhemerval Zanella, libc-alpha, Noah Goldstein
On 1/10/23 13:01, Adhemerval Zanella wrote:
> From: Richard Henderson <richard.henderson@linaro.org>
>
> While alpha has the more important string functions in assembly,
> there are still a few for find the generic routines are used.
>
> Use the CMPBGE insn, via the builtin, for testing of zeros. Use a
> simplified expansion of __builtin_ctz when the insn isn't available.
>
> Checked on alpha-linux-gnu.
> ---
> sysdeps/alpha/string-fzb.h | 52 +++++++++++++++++
> sysdeps/alpha/string-fzi.h | 113 +++++++++++++++++++++++++++++++++++++
> 2 files changed, 165 insertions(+)
> create mode 100644 sysdeps/alpha/string-fzb.h
> create mode 100644 sysdeps/alpha/string-fzi.h
>
> diff --git a/sysdeps/alpha/string-fzb.h b/sysdeps/alpha/string-fzb.h
> new file mode 100644
> index 0000000000..e3934ba413
> --- /dev/null
> +++ b/sysdeps/alpha/string-fzb.h
> @@ -0,0 +1,52 @@
> +/* Zero byte detection; boolean. Alpha version.
> + Copyright (C) 2023 Free Software Foundation, Inc.
> + This file is part of the GNU C Library.
> +
> + The GNU C Library is free software; you can redistribute it and/or
> + modify it under the terms of the GNU Lesser General Public
> + License as published by the Free Software Foundation; either
> + version 2.1 of the License, or (at your option) any later version.
> +
> + The GNU C Library is distributed in the hope that it will be useful,
> + but WITHOUT ANY WARRANTY; without even the implied warranty of
> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + Lesser General Public License for more details.
> +
> + You should have received a copy of the GNU Lesser General Public
> + License along with the GNU C Library; if not, see
> + <http://www.gnu.org/licenses/>. */
> +
> +#ifndef _STRING_FZB_H
> +#define _STRING_FZB_H 1
> +
> +#include <sys/cdefs.h>
> +#include <string-optype.h>
> +
> +/* Note that since CMPBGE creates a bit mask rather than a byte mask,
> + we cannot simply provide a target-specific string-fza.h. */
> +
> +/* Determine if any byte within X is zero. This is a pure boolean test. */
> +
> +static __always_inline _Bool
> +has_zero (op_t x)
> +{
> + return __builtin_alpha_cmpbge (0, x) != 0;
> +}
> +
> +/* Likewise, but for byte equality between X1 and X2. */
> +
> +static __always_inline _Bool
> +has_eq (op_t x1, op_t x2)
> +{
> + return has_zero (x1 ^ x2);
> +}
> +
> +/* Likewise, but for zeros in X1 and equal bytes between X1 and X2. */
> +
> +static __always_inline _Bool
> +has_zero_eq (op_t x1, op_t x2)
> +{
> + return has_zero (x1) | has_eq (x1, x2);
> +}
> +
> +#endif /* _STRING_FZB_H */
> diff --git a/sysdeps/alpha/string-fzi.h b/sysdeps/alpha/string-fzi.h
> new file mode 100644
> index 0000000000..bc2f0bdc91
> --- /dev/null
> +++ b/sysdeps/alpha/string-fzi.h
> @@ -0,0 +1,113 @@
> +/* string-fzi.h -- zero byte detection; indices. Alpha version.
> + Copyright (C) 2022 Free Software Foundation, Inc.
> + This file is part of the GNU C Library.
> +
> + The GNU C Library is free software; you can redistribute it and/or
> + modify it under the terms of the GNU Lesser General Public
> + License as published by the Free Software Foundation; either
> + version 2.1 of the License, or (at your option) any later version.
> +
> + The GNU C Library is distributed in the hope that it will be useful,
> + but WITHOUT ANY WARRANTY; without even the implied warranty of
> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + Lesser General Public License for more details.
> +
> + You should have received a copy of the GNU Lesser General Public
> + License along with the GNU C Library; if not, see
> + <http://www.gnu.org/licenses/>. */
> +
> +#ifndef _STRING_FZI_H
> +#define _STRING_FZI_H
> +
> +#include <limits.h>
> +#include <string-optype.h>
> +
> +/* Note that since CMPBGE creates a bit mask rather than a byte mask,
> + we cannot simply provide a target-specific string-fza.h. */
> +
> +/* A subroutine for the index_zero functions. Given a bitmask C,
> + return the index of the first bit set in memory order. */
> +
> +static __always_inline unsigned int
> +index_first (unsigned long int c)
> +{
> +#ifdef __alpha_cix__
> + return __builtin_ctzl (c);
> +#else
> + c = c & -c;
> + return (c & 0xf0 ? 4 : 0) + (c & 0xcc ? 2 : 0) + (c & 0xaa ? 1 : 0);
> +#endif
> +}
> +
> +/* Similarly, but return the (memory order) index of the last bit
> + that is non-zero. Note that only the least 8 bits may be nonzero. */
> +
> +static __always_inline unsigned int
> +index_last (unsigned long int x)
> +{
> +#ifdef __alpha_cix__
> + return __builtin_clzl (x) ^ 63;
> +#else
> + unsigned r = 0;
> + if (x & 0xf0)
> + r += 4;
> + if (x & (0xc << r))
> + r += 2;
> + if (x & (0x2 << r))
> + r += 1;
> + return r;
> +#endif
> +}
> +
> +/* Given a word X that is known to contain a zero byte, return the
> + index of the first such within the word in memory order. */
> +
> +static __always_inline unsigned int
> +index_first_zero (op_t x)
> +{
> + return index_first (__builtin_alpha_cmpbge (0, x));
The header split has drifted somewhat since the original: string-fza.h is missing and
check_mask() seems misplaced.
In particular, from strchrnul,
+ op_t mask = check_mask (find_zero_eq_all (word, repeated_c), s_int);
+ if (mask != 0)
+ return (char *) str + index_first (mask);
We're using the generic find_zero_eq_all, then (correctly, for the moment) the generic
check_mask, and then incorrectly the alpha-specific index_first.
We want to use an alpha-specific find_zero_eq_all (using cmpbge), an alpha-specific
check_mask (shifting by bits, not bytes), and an alpha-specific index_first (searching
only 8 low bits, not a full ctz).
I wonder if it makes sense to introduce a target-specific find_t, making it clear that
it's not the same type as op_t (for alpha, int instead of unsigned long (uint8_t having
it's own issues on ancient alpha ev5)).
I think check_mask (possibly renamed shift_find?) should belong in string-fza.h to match
the implementation therein, or within a new header (possibly along with find_t?).
Anyway, even the current set of headers would work, so long as Alpha implements all of them.
r~
^ permalink raw reply [flat|nested] 26+ messages in thread
* Re: [PATCH v6 03/17] Add string-maskoff.h generic header
2023-01-11 1:58 ` Richard Henderson
@ 2023-01-11 13:39 ` Adhemerval Zanella Netto
0 siblings, 0 replies; 26+ messages in thread
From: Adhemerval Zanella Netto @ 2023-01-11 13:39 UTC (permalink / raw)
To: Richard Henderson, libc-alpha, Noah Goldstein
On 10/01/23 22:58, Richard Henderson wrote:
> On 1/10/23 13:00, Adhemerval Zanella wrote:
>> +/* Return the address of the op_t word containing the address P. For
>> + instance on address 0x0011223344556677 and op_t with size of 8,
>> + it returns 0x0011223344556670. */
>> +static __always_inline op_t *
>> +word_containing (char const *p)
>> +{
>> + return (op_t *) ((uintptr_t) p & -sizeof(p));
>> +}
>
> sizeof(op_t).
Ack.
^ permalink raw reply [flat|nested] 26+ messages in thread
* Re: [PATCH v6 04/17] Add string vectorized find and detection functions
2023-01-11 2:25 ` Richard Henderson
@ 2023-01-11 13:42 ` Adhemerval Zanella Netto
2023-01-11 19:56 ` Noah Goldstein
0 siblings, 1 reply; 26+ messages in thread
From: Adhemerval Zanella Netto @ 2023-01-11 13:42 UTC (permalink / raw)
To: Richard Henderson, libc-alpha, Noah Goldstein
On 10/01/23 23:25, Richard Henderson wrote:
> On 1/10/23 13:00, Adhemerval Zanella wrote:
>> --- a/sysdeps/generic/string-maskoff.h
>> +++ b/sysdeps/generic/string-maskoff.h
>> @@ -23,7 +23,6 @@
>> #include <limits.h>
>> #include <stdint.h>
>> #include <string-optype.h>
>> -#include <string-fza.h>
>> /* Provide a mask based on the pointer alignment that sets up non-zero
>> bytes before the beginning of the word. It is used to mask off
>> @@ -44,12 +43,12 @@ create_mask (uintptr_t i)
>> /* Return the mask WORD shifted based on S_INT address value, to ignore
>> values not presented in the aligned word read. */
>> static __always_inline op_t
>> -check_mask (op_t word, uintptr_t s_int)
>> +check_mask (op_t word, uintptr_t s)
>> {
>> if (__BYTE_ORDER == __LITTLE_ENDIAN)
>> - return word >> (CHAR_BIT * (s_int % sizeof (s_int)));
>> + return word >> (CHAR_BIT * (s % sizeof (op_t)));
>> else
>> - return word << (CHAR_BIT * (s_int % sizeof (s_int)));
>> + return word << (CHAR_BIT * (s % sizeof (op_t)));
>> }
>
> Fold this into patch 3, if you want it.
Ack.
>
>> @@ -79,7 +78,7 @@ highbit_mask (op_t m)
>> static __always_inline op_t *
>> word_containing (char const *p)
>> {
>> - return (op_t *) ((uintptr_t) p & -sizeof(p));
>> + return (op_t *) ((op_t) p & -sizeof(p));
>
> Casting p to op_t is wrong.
Indeed, I will revert to uintptr_t.
^ permalink raw reply [flat|nested] 26+ messages in thread
* Re: [PATCH v6 14/17] alpha: Add string-fzb.h and string-fzi.h
2023-01-11 2:45 ` Richard Henderson
@ 2023-01-11 17:27 ` Adhemerval Zanella Netto
0 siblings, 0 replies; 26+ messages in thread
From: Adhemerval Zanella Netto @ 2023-01-11 17:27 UTC (permalink / raw)
To: Richard Henderson, libc-alpha, Noah Goldstein
On 10/01/23 23:45, Richard Henderson wrote:
> On 1/10/23 13:01, Adhemerval Zanella wrote:
>> From: Richard Henderson <richard.henderson@linaro.org>
>>
>> While alpha has the more important string functions in assembly,
>> there are still a few for find the generic routines are used.
>>
>> Use the CMPBGE insn, via the builtin, for testing of zeros. Use a
>> simplified expansion of __builtin_ctz when the insn isn't available.
>>
>> Checked on alpha-linux-gnu.
>> ---
>> sysdeps/alpha/string-fzb.h | 52 +++++++++++++++++
>> sysdeps/alpha/string-fzi.h | 113 +++++++++++++++++++++++++++++++++++++
>> 2 files changed, 165 insertions(+)
>> create mode 100644 sysdeps/alpha/string-fzb.h
>> create mode 100644 sysdeps/alpha/string-fzi.h
>>
>> diff --git a/sysdeps/alpha/string-fzb.h b/sysdeps/alpha/string-fzb.h
>> new file mode 100644
>> index 0000000000..e3934ba413
>> --- /dev/null
>> +++ b/sysdeps/alpha/string-fzb.h
>> @@ -0,0 +1,52 @@
>> +/* Zero byte detection; boolean. Alpha version.
>> + Copyright (C) 2023 Free Software Foundation, Inc.
>> + This file is part of the GNU C Library.
>> +
>> + The GNU C Library is free software; you can redistribute it and/or
>> + modify it under the terms of the GNU Lesser General Public
>> + License as published by the Free Software Foundation; either
>> + version 2.1 of the License, or (at your option) any later version.
>> +
>> + The GNU C Library is distributed in the hope that it will be useful,
>> + but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
>> + Lesser General Public License for more details.
>> +
>> + You should have received a copy of the GNU Lesser General Public
>> + License along with the GNU C Library; if not, see
>> + <http://www.gnu.org/licenses/>. */
>> +
>> +#ifndef _STRING_FZB_H
>> +#define _STRING_FZB_H 1
>> +
>> +#include <sys/cdefs.h>
>> +#include <string-optype.h>
>> +
>> +/* Note that since CMPBGE creates a bit mask rather than a byte mask,
>> + we cannot simply provide a target-specific string-fza.h. */
>> +
>> +/* Determine if any byte within X is zero. This is a pure boolean test. */
>> +
>> +static __always_inline _Bool
>> +has_zero (op_t x)
>> +{
>> + return __builtin_alpha_cmpbge (0, x) != 0;
>> +}
>> +
>> +/* Likewise, but for byte equality between X1 and X2. */
>> +
>> +static __always_inline _Bool
>> +has_eq (op_t x1, op_t x2)
>> +{
>> + return has_zero (x1 ^ x2);
>> +}
>> +
>> +/* Likewise, but for zeros in X1 and equal bytes between X1 and X2. */
>> +
>> +static __always_inline _Bool
>> +has_zero_eq (op_t x1, op_t x2)
>> +{
>> + return has_zero (x1) | has_eq (x1, x2);
>> +}
>> +
>> +#endif /* _STRING_FZB_H */
>> diff --git a/sysdeps/alpha/string-fzi.h b/sysdeps/alpha/string-fzi.h
>> new file mode 100644
>> index 0000000000..bc2f0bdc91
>> --- /dev/null
>> +++ b/sysdeps/alpha/string-fzi.h
>> @@ -0,0 +1,113 @@
>> +/* string-fzi.h -- zero byte detection; indices. Alpha version.
>> + Copyright (C) 2022 Free Software Foundation, Inc.
>> + This file is part of the GNU C Library.
>> +
>> + The GNU C Library is free software; you can redistribute it and/or
>> + modify it under the terms of the GNU Lesser General Public
>> + License as published by the Free Software Foundation; either
>> + version 2.1 of the License, or (at your option) any later version.
>> +
>> + The GNU C Library is distributed in the hope that it will be useful,
>> + but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
>> + Lesser General Public License for more details.
>> +
>> + You should have received a copy of the GNU Lesser General Public
>> + License along with the GNU C Library; if not, see
>> + <http://www.gnu.org/licenses/>. */
>> +
>> +#ifndef _STRING_FZI_H
>> +#define _STRING_FZI_H
>> +
>> +#include <limits.h>
>> +#include <string-optype.h>
>> +
>> +/* Note that since CMPBGE creates a bit mask rather than a byte mask,
>> + we cannot simply provide a target-specific string-fza.h. */
>> +
>> +/* A subroutine for the index_zero functions. Given a bitmask C,
>> + return the index of the first bit set in memory order. */
>> +
>> +static __always_inline unsigned int
>> +index_first (unsigned long int c)
>> +{
>> +#ifdef __alpha_cix__
>> + return __builtin_ctzl (c);
>> +#else
>> + c = c & -c;
>> + return (c & 0xf0 ? 4 : 0) + (c & 0xcc ? 2 : 0) + (c & 0xaa ? 1 : 0);
>> +#endif
>> +}
>> +
>> +/* Similarly, but return the (memory order) index of the last bit
>> + that is non-zero. Note that only the least 8 bits may be nonzero. */
>> +
>> +static __always_inline unsigned int
>> +index_last (unsigned long int x)
>> +{
>> +#ifdef __alpha_cix__
>> + return __builtin_clzl (x) ^ 63;
>> +#else
>> + unsigned r = 0;
>> + if (x & 0xf0)
>> + r += 4;
>> + if (x & (0xc << r))
>> + r += 2;
>> + if (x & (0x2 << r))
>> + r += 1;
>> + return r;
>> +#endif
>> +}
>> +
>> +/* Given a word X that is known to contain a zero byte, return the
>> + index of the first such within the word in memory order. */
>> +
>> +static __always_inline unsigned int
>> +index_first_zero (op_t x)
>> +{
>> + return index_first (__builtin_alpha_cmpbge (0, x));
>
> The header split has drifted somewhat since the original: string-fza.h is missing and check_mask() seems misplaced.
>
> In particular, from strchrnul,
>
>
> + op_t mask = check_mask (find_zero_eq_all (word, repeated_c), s_int);
> + if (mask != 0)
> + return (char *) str + index_first (mask);
>
>
> We're using the generic find_zero_eq_all, then (correctly, for the moment) the generic check_mask, and then incorrectly the alpha-specific index_first.
>
> We want to use an alpha-specific find_zero_eq_all (using cmpbge), an alpha-specific check_mask (shifting by bits, not bytes), and an alpha-specific index_first (searching only 8 low bits, not a full ctz).
Right, I had to consult the alpha manual to remind that cmpbge sets the lower
8 bits of the target register. And indeed running on qemu-users triggers a lot
of issues.
>
> I wonder if it makes sense to introduce a target-specific find_t, making it clear that it's not the same type as op_t (for alpha, int instead of unsigned long (uint8_t having it's own issues on ancient alpha ev5)).
I think it makes sense, I will add this change.
>
> I think check_mask (possibly renamed shift_find?) should belong in string-fza.h to match the implementation therein, or within a new header (possibly along with find_t?).
It also make sense.
>
> Anyway, even the current set of headers would work, so long as Alpha implements all of them.
A alpha-specific string-fza.h is in fact quite simple, since we do not need to implement
all the function.
I will update the patch with your suggestions.
^ permalink raw reply [flat|nested] 26+ messages in thread
* Re: [PATCH v6 04/17] Add string vectorized find and detection functions
2023-01-11 13:42 ` Adhemerval Zanella Netto
@ 2023-01-11 19:56 ` Noah Goldstein
0 siblings, 0 replies; 26+ messages in thread
From: Noah Goldstein @ 2023-01-11 19:56 UTC (permalink / raw)
To: Adhemerval Zanella Netto; +Cc: Richard Henderson, libc-alpha
On Wed, Jan 11, 2023 at 5:42 AM Adhemerval Zanella Netto
<adhemerval.zanella@linaro.org> wrote:
>
>
>
> On 10/01/23 23:25, Richard Henderson wrote:
> > On 1/10/23 13:00, Adhemerval Zanella wrote:
> >> --- a/sysdeps/generic/string-maskoff.h
> >> +++ b/sysdeps/generic/string-maskoff.h
> >> @@ -23,7 +23,6 @@
> >> #include <limits.h>
> >> #include <stdint.h>
> >> #include <string-optype.h>
> >> -#include <string-fza.h>
> >> /* Provide a mask based on the pointer alignment that sets up non-zero
> >> bytes before the beginning of the word. It is used to mask off
> >> @@ -44,12 +43,12 @@ create_mask (uintptr_t i)
> >> /* Return the mask WORD shifted based on S_INT address value, to ignore
> >> values not presented in the aligned word read. */
> >> static __always_inline op_t
> >> -check_mask (op_t word, uintptr_t s_int)
> >> +check_mask (op_t word, uintptr_t s)
> >> {
> >> if (__BYTE_ORDER == __LITTLE_ENDIAN)
> >> - return word >> (CHAR_BIT * (s_int % sizeof (s_int)));
> >> + return word >> (CHAR_BIT * (s % sizeof (op_t)));
> >> else
> >> - return word << (CHAR_BIT * (s_int % sizeof (s_int)));
> >> + return word << (CHAR_BIT * (s % sizeof (op_t)));
> >> }
> >
> > Fold this into patch 3, if you want it.
>
> Ack.
>
> >
> >> @@ -79,7 +78,7 @@ highbit_mask (op_t m)
> >> static __always_inline op_t *
> >> word_containing (char const *p)
> >> {
> >> - return (op_t *) ((uintptr_t) p & -sizeof(p));
> >> + return (op_t *) ((op_t) p & -sizeof(p));
> >
> > Casting p to op_t is wrong.
>
> Indeed, I will revert to uintptr_t.
If sizeof (op_t) > sizeof(uintptr_t) won't this be able to
leave us with a misaligned read + potential fault?
^ permalink raw reply [flat|nested] 26+ messages in thread
end of thread, other threads:[~2023-01-11 19:56 UTC | newest]
Thread overview: 26+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2023-01-10 21:00 [PATCH v6 00/17] Improve generic string routines Adhemerval Zanella
2023-01-10 21:00 ` [PATCH v6 01/17] Parameterize op_t from memcopy.h Adhemerval Zanella
2023-01-10 21:00 ` [PATCH v6 02/17] Parameterize OP_T_THRES " Adhemerval Zanella
2023-01-10 21:00 ` [PATCH v6 03/17] Add string-maskoff.h generic header Adhemerval Zanella
2023-01-11 1:58 ` Richard Henderson
2023-01-11 13:39 ` Adhemerval Zanella Netto
2023-01-10 21:00 ` [PATCH v6 04/17] Add string vectorized find and detection functions Adhemerval Zanella
2023-01-11 2:25 ` Richard Henderson
2023-01-11 13:42 ` Adhemerval Zanella Netto
2023-01-11 19:56 ` Noah Goldstein
2023-01-10 21:00 ` [PATCH v6 05/17] string: Improve generic strlen Adhemerval Zanella
2023-01-10 21:00 ` [PATCH v6 06/17] string: Improve generic strnlen Adhemerval Zanella
2023-01-10 21:00 ` [PATCH v6 07/17] string: Improve generic strchr Adhemerval Zanella
2023-01-10 21:00 ` [PATCH v6 08/17] string: Improve generic strchrnul Adhemerval Zanella
2023-01-10 21:00 ` [PATCH v6 09/17] string: Improve generic strcmp Adhemerval Zanella
2023-01-10 21:00 ` [PATCH v6 10/17] string: Improve generic memchr Adhemerval Zanella
2023-01-10 21:01 ` [PATCH v6 11/17] string: Improve generic memrchr Adhemerval Zanella
2023-01-10 21:01 ` [PATCH v6 12/17] hppa: Add memcopy.h Adhemerval Zanella
2023-01-10 21:01 ` [PATCH v6 13/17] hppa: Add string-fzb.h and string-fzi.h Adhemerval Zanella
2023-01-10 21:01 ` [PATCH v6 14/17] alpha: " Adhemerval Zanella
2023-01-11 2:45 ` Richard Henderson
2023-01-11 17:27 ` Adhemerval Zanella Netto
2023-01-10 21:01 ` [PATCH v6 15/17] arm: Add string-fza.h Adhemerval Zanella
2023-01-10 21:01 ` [PATCH v6 16/17] powerpc: " Adhemerval Zanella
2023-01-11 1:18 ` Carlos Seo
2023-01-10 21:01 ` [PATCH v6 17/17] sh: Add string-fzb.h Adhemerval Zanella
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