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* [glibc] x86: Use dl-symbol-redir-ifunc.h on cpu-tunables
@ 2023-11-21 20:49 Adhemerval Zanella
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From: Adhemerval Zanella @ 2023-11-21 20:49 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=4862d546c04bd2caf496d48335a546c0a44ad4a5
commit 4862d546c04bd2caf496d48335a546c0a44ad4a5
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Mon Nov 6 17:25:42 2023 -0300
x86: Use dl-symbol-redir-ifunc.h on cpu-tunables
The dl-symbol-redir-ifunc.h redirects compiler-generated libcalls to
arch-specific memory implementations to avoid ifunc calls where it is not
yet possible. The memcmp-isa-default-impl.h aims to fix the same issue
by calling the specific memset implementation directly.
Using the memcmp symbol directly allows the compiler to inline the memset
calls (especially because _dl_tunable_set_hwcaps uses constants values),
generating better code.
Checked on x86_64-linux-gnu.
Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com>
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Diff:
---
.../i386/i686/multiarch/dl-symbol-redir-ifunc.h | 5 +++
sysdeps/x86/cpu-tunables.c | 39 +++++++---------------
sysdeps/x86_64/memcmp-isa-default-impl.h | 28 ----------------
sysdeps/x86_64/multiarch/dl-symbol-redir-ifunc.h | 15 +++++++++
4 files changed, 32 insertions(+), 55 deletions(-)
diff --git a/sysdeps/i386/i686/multiarch/dl-symbol-redir-ifunc.h b/sysdeps/i386/i686/multiarch/dl-symbol-redir-ifunc.h
index dee69d19db..220c586bd2 100644
--- a/sysdeps/i386/i686/multiarch/dl-symbol-redir-ifunc.h
+++ b/sysdeps/i386/i686/multiarch/dl-symbol-redir-ifunc.h
@@ -19,6 +19,11 @@
#ifndef _DL_IFUNC_GENERIC_H
#define _DL_IFUNC_GENERIC_H
+#ifndef SHARED
+
asm ("memset = __memset_ia32");
+asm ("memcmp = __memcmp_ia32");
+
+#endif /* SHARED */
#endif
diff --git a/sysdeps/x86/cpu-tunables.c b/sysdeps/x86/cpu-tunables.c
index 0d4f328585..5697885226 100644
--- a/sysdeps/x86/cpu-tunables.c
+++ b/sysdeps/x86/cpu-tunables.c
@@ -24,24 +24,11 @@
#include <string.h>
#include <cpu-features.h>
#include <ldsodefs.h>
-
-/* We can't use IFUNC memcmp nor strlen in init_cpu_features from libc.a
- since IFUNC must be set up by init_cpu_features. */
-#if defined USE_MULTIARCH && !defined SHARED
-# ifdef __x86_64__
-/* DEFAULT_MEMCMP by sysdeps/x86_64/memcmp-isa-default-impl.h. */
-# include <sysdeps/x86_64/memcmp-isa-default-impl.h>
-# else
-# define DEFAULT_MEMCMP __memcmp_ia32
-# endif
-extern __typeof (memcmp) DEFAULT_MEMCMP;
-#else
-# define DEFAULT_MEMCMP memcmp
-#endif
+#include <dl-symbol-redir-ifunc.h>
#define CHECK_GLIBC_IFUNC_CPU_OFF(f, cpu_features, name, len) \
_Static_assert (sizeof (#name) - 1 == len, #name " != " #len); \
- if (!DEFAULT_MEMCMP (f, #name, len)) \
+ if (memcmp (f, #name, len) == 0) \
{ \
CPU_FEATURE_UNSET (cpu_features, name) \
break; \
@@ -51,7 +38,7 @@ extern __typeof (memcmp) DEFAULT_MEMCMP;
which isn't available. */
#define CHECK_GLIBC_IFUNC_PREFERRED_OFF(f, cpu_features, name, len) \
_Static_assert (sizeof (#name) - 1 == len, #name " != " #len); \
- if (!DEFAULT_MEMCMP (f, #name, len)) \
+ if (memcmp (f, #name, len) == 0) \
{ \
cpu_features->preferred[index_arch_##name] \
&= ~bit_arch_##name; \
@@ -62,7 +49,7 @@ extern __typeof (memcmp) DEFAULT_MEMCMP;
#define CHECK_GLIBC_IFUNC_PREFERRED_BOTH(f, cpu_features, name, \
disable, len) \
_Static_assert (sizeof (#name) - 1 == len, #name " != " #len); \
- if (!DEFAULT_MEMCMP (f, #name, len)) \
+ if (memcmp (f, #name, len) == 0) \
{ \
if (disable) \
cpu_features->preferred[index_arch_##name] &= ~bit_arch_##name; \
@@ -76,7 +63,7 @@ extern __typeof (memcmp) DEFAULT_MEMCMP;
#define CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH(f, cpu_features, name, \
need, disable, len) \
_Static_assert (sizeof (#name) - 1 == len, #name " != " #len); \
- if (!DEFAULT_MEMCMP (f, #name, len)) \
+ if (memcmp (f, #name, len) == 0) \
{ \
if (disable) \
cpu_features->preferred[index_arch_##name] &= ~bit_arch_##name; \
@@ -177,7 +164,7 @@ TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *valp)
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, POPCNT, 6);
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, SSE4_1, 6);
CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, SSE4_2, 6);
- if (!DEFAULT_MEMCMP (n, "XSAVEC", 6))
+ if (memcmp (n, "XSAVEC", 6) == 0)
{
/* Update xsave_state_size to XSAVE state size. */
cpu_features->xsave_state_size
@@ -290,12 +277,11 @@ attribute_hidden
void
TUNABLE_CALLBACK (set_x86_ibt) (tunable_val_t *valp)
{
- if (DEFAULT_MEMCMP (valp->strval, "on", sizeof ("on")) == 0)
+ if (memcmp (valp->strval, "on", sizeof ("on")) == 0)
GL(dl_x86_feature_control).ibt = cet_always_on;
- else if (DEFAULT_MEMCMP (valp->strval, "off", sizeof ("off")) == 0)
+ else if (memcmp (valp->strval, "off", sizeof ("off")) == 0)
GL(dl_x86_feature_control).ibt = cet_always_off;
- else if (DEFAULT_MEMCMP (valp->strval, "permissive",
- sizeof ("permissive")) == 0)
+ else if (memcmp (valp->strval, "permissive", sizeof ("permissive")) == 0)
GL(dl_x86_feature_control).ibt = cet_permissive;
}
@@ -303,12 +289,11 @@ attribute_hidden
void
TUNABLE_CALLBACK (set_x86_shstk) (tunable_val_t *valp)
{
- if (DEFAULT_MEMCMP (valp->strval, "on", sizeof ("on")) == 0)
+ if (memcmp (valp->strval, "on", sizeof ("on")) == 0)
GL(dl_x86_feature_control).shstk = cet_always_on;
- else if (DEFAULT_MEMCMP (valp->strval, "off", sizeof ("off")) == 0)
+ else if (memcmp (valp->strval, "off", sizeof ("off")) == 0)
GL(dl_x86_feature_control).shstk = cet_always_off;
- else if (DEFAULT_MEMCMP (valp->strval, "permissive",
- sizeof ("permissive")) == 0)
+ else if (memcmp (valp->strval, "permissive", sizeof ("permissive")) == 0)
GL(dl_x86_feature_control).shstk = cet_permissive;
}
#endif
diff --git a/sysdeps/x86_64/memcmp-isa-default-impl.h b/sysdeps/x86_64/memcmp-isa-default-impl.h
deleted file mode 100644
index 0962e83c3d..0000000000
--- a/sysdeps/x86_64/memcmp-isa-default-impl.h
+++ /dev/null
@@ -1,28 +0,0 @@
-/* Set default memcmp impl based on ISA level.
- Copyright (C) 2022-2023 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
- <https://www.gnu.org/licenses/>. */
-
-#include <isa-level.h>
-#if MINIMUM_X86_ISA_LEVEL == 1 || MINIMUM_X86_ISA_LEVEL == 2
-# define DEFAULT_MEMCMP __memcmp_sse2
-#elif MINIMUM_X86_ISA_LEVEL == 3
-# define DEFAULT_MEMCMP __memcmp_avx2_movbe
-#elif MINIMUM_X86_ISA_LEVEL == 4
-# define DEFAULT_MEMCMP __memcmp_evex_movbe
-#else
-# error "Unknown default memcmp implementation"
-#endif
diff --git a/sysdeps/x86_64/multiarch/dl-symbol-redir-ifunc.h b/sysdeps/x86_64/multiarch/dl-symbol-redir-ifunc.h
index 3fe73ca1c3..c7d8961bb6 100644
--- a/sysdeps/x86_64/multiarch/dl-symbol-redir-ifunc.h
+++ b/sysdeps/x86_64/multiarch/dl-symbol-redir-ifunc.h
@@ -19,6 +19,8 @@
#ifndef _DL_IFUNC_GENERIC_H
#define _DL_IFUNC_GENERIC_H
+#ifndef SHARED
+
#include <isa-level.h>
#if MINIMUM_X86_ISA_LEVEL >= 4
@@ -31,4 +33,17 @@
asm ("memset = " HAVE_MEMSET_IFUNC_GENERIC);
+
+#if MINIMUM_X86_ISA_LEVEL >= 4
+# define HAVE_MEMCMP_IFUNC_GENERIC "__memcmp_evex_movbe"
+#elif MINIMUM_X86_ISA_LEVEL == 3
+# define HAVE_MEMCMP_IFUNC_GENERIC "__memcmp_avx2_movbe"
+#else
+# define HAVE_MEMCMP_IFUNC_GENERIC "__memcmp_sse2"
+#endif
+
+asm ("memcmp = " HAVE_MEMCMP_IFUNC_GENERIC);
+
+#endif /* SHARED */
+
#endif
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