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* [PATCH v6] x86_64: Correct THREAD_SETMEM/THREAD_SETMEM_NC for movq [BZ #27591]
@ 2021-03-19 18:35 H.J. Lu
  2021-04-01 13:51 ` Carlos O'Donell
  0 siblings, 1 reply; 4+ messages in thread
From: H.J. Lu @ 2021-03-19 18:35 UTC (permalink / raw)
  To: libc-alpha

config/i386/constraints.md in GCC has

(define_constraint "e"
  "32-bit signed integer constant, or a symbolic reference known
   to fit that range (for immediate operands in sign-extending x86-64
   instructions)."
  (match_operand 0 "x86_64_immediate_operand"))

Since movq takes a signed 32-bit immediate or a register source operand,
use "er", instead of "nr"/"ir", constraint for 32-bit signed integer
constant or register on movq.
---
 sysdeps/x86_64/Makefile           |  2 +
 sysdeps/x86_64/nptl/tls.h         | 10 ++++-
 sysdeps/x86_64/tst-x86-64-tls-1.c | 64 +++++++++++++++++++++++++++++++
 3 files changed, 74 insertions(+), 2 deletions(-)
 create mode 100644 sysdeps/x86_64/tst-x86-64-tls-1.c

diff --git a/sysdeps/x86_64/Makefile b/sysdeps/x86_64/Makefile
index d1d7cb9d2e..06a444b6af 100644
--- a/sysdeps/x86_64/Makefile
+++ b/sysdeps/x86_64/Makefile
@@ -183,6 +183,8 @@ ifeq (no,$(build-hardcoded-path-in-tests))
 tests-container += tst-glibc-hwcaps-cache
 endif
 
+tests-internal += tst-x86-64-tls-1
+
 endif # $(subdir) == elf
 
 ifeq ($(subdir),csu)
diff --git a/sysdeps/x86_64/nptl/tls.h b/sysdeps/x86_64/nptl/tls.h
index 20f0958780..a78c4f4d01 100644
--- a/sysdeps/x86_64/nptl/tls.h
+++ b/sysdeps/x86_64/nptl/tls.h
@@ -271,8 +271,11 @@ _Static_assert (offsetof (tcbhead_t, __glibc_unused2) == 0x80,
 		       "i" (offsetof (struct pthread, member)));	      \
      else /* 8 */							      \
        {								      \
+	 /* Since movq takes a signed 32-bit immediate or a register source   \
+	    operand, use "er" constraint for 32-bit signed integer constant   \
+	    or register.  */						      \
 	 asm volatile ("movq %q0,%%fs:%P1" :				      \
-		       : IMM_MODE ((uint64_t) cast_to_integer (value)),	      \
+		       : "er" ((uint64_t) cast_to_integer (value)),	      \
 			 "i" (offsetof (struct pthread, member)));	      \
        }})
 
@@ -296,8 +299,11 @@ _Static_assert (offsetof (tcbhead_t, __glibc_unused2) == 0x80,
 		       "r" (idx));					      \
      else /* 8 */							      \
        {								      \
+	 /* Since movq takes a signed 32-bit immediate or a register source   \
+	    operand, use "er" constraint for 32-bit signed integer constant   \
+	    or register.  */						      \
 	 asm volatile ("movq %q0,%%fs:%P1(,%q2,8)" :			      \
-		       : IMM_MODE ((uint64_t) cast_to_integer (value)),	      \
+		       : "er" ((uint64_t) cast_to_integer (value)),	      \
 			 "i" (offsetof (struct pthread, member[0])),	      \
 			 "r" (idx));					      \
        }})
diff --git a/sysdeps/x86_64/tst-x86-64-tls-1.c b/sysdeps/x86_64/tst-x86-64-tls-1.c
new file mode 100644
index 0000000000..354635884e
--- /dev/null
+++ b/sysdeps/x86_64/tst-x86-64-tls-1.c
@@ -0,0 +1,64 @@
+/* Test THREAD_SETMEM and THREAD_SETMEM_NC for IMM64.
+   Copyright (C) 2021 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 <tls.h>
+#include <support/check.h>
+
+static int
+do_test (void)
+{
+  unsigned long long int saved_ssp_base, ssp_base;
+  saved_ssp_base = THREAD_GETMEM (THREAD_SELF, header.ssp_base);
+
+  THREAD_SETMEM (THREAD_SELF, header.ssp_base, (1ULL << 57) - 1);
+  ssp_base = THREAD_GETMEM (THREAD_SELF, header.ssp_base);
+  if (ssp_base != ((1ULL << 57) - 1))
+    FAIL_EXIT1 ("THREAD_SETMEM: 0x%llx != 0x%llx",
+		ssp_base, (1ULL << 57) - 1);
+
+  THREAD_SETMEM (THREAD_SELF, header.ssp_base, -1ULL);
+  ssp_base = THREAD_GETMEM (THREAD_SELF, header.ssp_base);
+  if (ssp_base != -1ULL)
+    FAIL_EXIT1 ("THREAD_SETMEM: 0x%llx != 0x%llx", ssp_base, -1ULL);
+
+  THREAD_SETMEM (THREAD_SELF, header.ssp_base, saved_ssp_base);
+#ifndef __ILP32__
+  struct pthread_key_data *saved_specific, *specific;
+  saved_specific = THREAD_GETMEM_NC (THREAD_SELF, specific, 1);
+
+  uintptr_t value = (1UL << 57) - 1;
+  THREAD_SETMEM_NC (THREAD_SELF, specific, 1,
+		    (struct pthread_key_data *) value);
+  specific = THREAD_GETMEM_NC (THREAD_SELF, specific, 1);
+  if (specific != (struct pthread_key_data *) value)
+    FAIL_EXIT1 ("THREAD_GETMEM_NC: %p != %p",
+		specific, (struct pthread_key_data *) value);
+
+  THREAD_SETMEM_NC (THREAD_SELF, specific, 1,
+		    (struct pthread_key_data *) -1UL);
+  specific = THREAD_GETMEM_NC (THREAD_SELF, specific, 1);
+  if (specific != (struct pthread_key_data *) -1UL)
+    FAIL_EXIT1 ("THREAD_GETMEM_NC: %p != %p",
+		specific, (struct pthread_key_data *) -1UL);
+
+  THREAD_SETMEM_NC (THREAD_SELF, specific, 1, saved_specific);
+#endif
+  return 0;
+}
+
+#include <support/test-driver.c>
-- 
2.30.2


^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH v6] x86_64: Correct THREAD_SETMEM/THREAD_SETMEM_NC for movq [BZ #27591]
  2021-03-19 18:35 [PATCH v6] x86_64: Correct THREAD_SETMEM/THREAD_SETMEM_NC for movq [BZ #27591] H.J. Lu
@ 2021-04-01 13:51 ` Carlos O'Donell
  0 siblings, 0 replies; 4+ messages in thread
From: Carlos O'Donell @ 2021-04-01 13:51 UTC (permalink / raw)
  To: H.J. Lu, libc-alpha

On 3/19/21 2:35 PM, H.J. Lu via Libc-alpha wrote:
> config/i386/constraints.md in GCC has
> 
> (define_constraint "e"
>   "32-bit signed integer constant, or a symbolic reference known
>    to fit that range (for immediate operands in sign-extending x86-64
>    instructions)."
>   (match_operand 0 "x86_64_immediate_operand"))
> 
> Since movq takes a signed 32-bit immediate or a register source operand,
> use "er", instead of "nr"/"ir", constraint for 32-bit signed integer
> constant or register on movq.

v6, and this version looks amazing, much better than before and I think
we've arrived a good solution to this problem. Thank you for your efforts
and working through the details.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

> ---
>  sysdeps/x86_64/Makefile           |  2 +
>  sysdeps/x86_64/nptl/tls.h         | 10 ++++-
>  sysdeps/x86_64/tst-x86-64-tls-1.c | 64 +++++++++++++++++++++++++++++++
>  3 files changed, 74 insertions(+), 2 deletions(-)
>  create mode 100644 sysdeps/x86_64/tst-x86-64-tls-1.c
> 
> diff --git a/sysdeps/x86_64/Makefile b/sysdeps/x86_64/Makefile
> index d1d7cb9d2e..06a444b6af 100644
> --- a/sysdeps/x86_64/Makefile
> +++ b/sysdeps/x86_64/Makefile
> @@ -183,6 +183,8 @@ ifeq (no,$(build-hardcoded-path-in-tests))
>  tests-container += tst-glibc-hwcaps-cache
>  endif
>  
> +tests-internal += tst-x86-64-tls-1

OK. Test is internal with use of tls.h header.

> +
>  endif # $(subdir) == elf
>  
>  ifeq ($(subdir),csu)
> diff --git a/sysdeps/x86_64/nptl/tls.h b/sysdeps/x86_64/nptl/tls.h
> index 20f0958780..a78c4f4d01 100644
> --- a/sysdeps/x86_64/nptl/tls.h
> +++ b/sysdeps/x86_64/nptl/tls.h
> @@ -271,8 +271,11 @@ _Static_assert (offsetof (tcbhead_t, __glibc_unused2) == 0x80,
>  		       "i" (offsetof (struct pthread, member)));	      \
>       else /* 8 */							      \
>         {								      \
> +	 /* Since movq takes a signed 32-bit immediate or a register source   \
> +	    operand, use "er" constraint for 32-bit signed integer constant   \
> +	    or register.  */						      \
>  	 asm volatile ("movq %q0,%%fs:%P1" :				      \
> -		       : IMM_MODE ((uint64_t) cast_to_integer (value)),	      \
> +		       : "er" ((uint64_t) cast_to_integer (value)),	      \

OK. Great change, very clear, and uses immediate or register to get it to work.

>  			 "i" (offsetof (struct pthread, member)));	      \
>         }})
>  
> @@ -296,8 +299,11 @@ _Static_assert (offsetof (tcbhead_t, __glibc_unused2) == 0x80,
>  		       "r" (idx));					      \
>       else /* 8 */							      \
>         {								      \
> +	 /* Since movq takes a signed 32-bit immediate or a register source   \
> +	    operand, use "er" constraint for 32-bit signed integer constant   \
> +	    or register.  */						      \
>  	 asm volatile ("movq %q0,%%fs:%P1(,%q2,8)" :			      \
> -		       : IMM_MODE ((uint64_t) cast_to_integer (value)),	      \
> +		       : "er" ((uint64_t) cast_to_integer (value)),	      \
>  			 "i" (offsetof (struct pthread, member[0])),	      \

OK.

>  			 "r" (idx));					      \
>         }})
> diff --git a/sysdeps/x86_64/tst-x86-64-tls-1.c b/sysdeps/x86_64/tst-x86-64-tls-1.c
> new file mode 100644
> index 0000000000..354635884e
> --- /dev/null
> +++ b/sysdeps/x86_64/tst-x86-64-tls-1.c
> @@ -0,0 +1,64 @@
> +/* Test THREAD_SETMEM and THREAD_SETMEM_NC for IMM64.
> +   Copyright (C) 2021 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 <tls.h>
> +#include <support/check.h>
> +
> +static int
> +do_test (void)
> +{
> +  unsigned long long int saved_ssp_base, ssp_base;
> +  saved_ssp_base = THREAD_GETMEM (THREAD_SELF, header.ssp_base);
> +
> +  THREAD_SETMEM (THREAD_SELF, header.ssp_base, (1ULL << 57) - 1);
> +  ssp_base = THREAD_GETMEM (THREAD_SELF, header.ssp_base);
> +  if (ssp_base != ((1ULL << 57) - 1))
> +    FAIL_EXIT1 ("THREAD_SETMEM: 0x%llx != 0x%llx",
> +		ssp_base, (1ULL << 57) - 1);
> +
> +  THREAD_SETMEM (THREAD_SELF, header.ssp_base, -1ULL);
> +  ssp_base = THREAD_GETMEM (THREAD_SELF, header.ssp_base);
> +  if (ssp_base != -1ULL)
> +    FAIL_EXIT1 ("THREAD_SETMEM: 0x%llx != 0x%llx", ssp_base, -1ULL);
> +
> +  THREAD_SETMEM (THREAD_SELF, header.ssp_base, saved_ssp_base);
> +#ifndef __ILP32__
> +  struct pthread_key_data *saved_specific, *specific;
> +  saved_specific = THREAD_GETMEM_NC (THREAD_SELF, specific, 1);
> +
> +  uintptr_t value = (1UL << 57) - 1;
> +  THREAD_SETMEM_NC (THREAD_SELF, specific, 1,
> +		    (struct pthread_key_data *) value);
> +  specific = THREAD_GETMEM_NC (THREAD_SELF, specific, 1);
> +  if (specific != (struct pthread_key_data *) value)
> +    FAIL_EXIT1 ("THREAD_GETMEM_NC: %p != %p",
> +		specific, (struct pthread_key_data *) value);
> +
> +  THREAD_SETMEM_NC (THREAD_SELF, specific, 1,
> +		    (struct pthread_key_data *) -1UL);
> +  specific = THREAD_GETMEM_NC (THREAD_SELF, specific, 1);
> +  if (specific != (struct pthread_key_data *) -1UL)
> +    FAIL_EXIT1 ("THREAD_GETMEM_NC: %p != %p",
> +		specific, (struct pthread_key_data *) -1UL);
> +
> +  THREAD_SETMEM_NC (THREAD_SELF, specific, 1, saved_specific);
> +#endif
> +  return 0;
> +}
> +
> +#include <support/test-driver.c>

OK.

> 


-- 
Cheers,
Carlos.


^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH v6] x86_64: Correct THREAD_SETMEM/THREAD_SETMEM_NC for movq [BZ #27591]
  2021-03-16 16:50                         ` [PATCH v6] x86_64: Correct THREAD_SETMEM/THREAD_SETMEM_NC for movq " H.J. Lu
@ 2021-03-16 16:52                           ` H.J. Lu
  0 siblings, 0 replies; 4+ messages in thread
From: H.J. Lu @ 2021-03-16 16:52 UTC (permalink / raw)
  To: Carlos O'Donell
  Cc: Florian Weimer, Andreas Schwab, Carlos O'Donell via Libc-alpha

[-- Attachment #1: Type: text/plain, Size: 1257 bytes --]

On Tue, Mar 16, 2021 at 9:50 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Tue, Mar 16, 2021 at 9:34 AM Carlos O'Donell <carlos@redhat.com> wrote:
> >
> > On 3/16/21 12:10 PM, Florian Weimer via Libc-alpha wrote:
> > > * Andreas Schwab:
> > >
> > >> I don't think this will work in general.  Wouldn't it be possible that
> > >> an operands optimizes to a 64-bit constant in later passes?  What you
> > >> really need is a constraint that only matches a 32-bit immediate or a
> > >> register.  Like "rWf"?
>
> config/i386/constraints.md in GCC has
>
> (define_constraint "e"
>   "32-bit signed integer constant, or a symbolic reference known
>    to fit that range (for immediate operands in sign-extending x86-64
>    instructions)."
>   (match_operand 0 "x86_64_immediate_operand"))
>
> "er" is the correct constraint for movq.
>
> > > Maybe we should to the __seg_fs namespace instead?  Wouldn't that avoid
> > > these issues?
> >
> > It might.
> >
> > HJ, Does it work to rewrite this using __seg_fs?
>
> I tried it.  GCC generates worse code.
>
> > Otherwise I'll review v5, which I think is better than it was before and
> > makes forward progress.
>
> Here is the v6 patch to use the "er" constraint.   OK for master?
>

Include the patch.

-- 
H.J.

[-- Attachment #2: v6-0001-x86_64-Correct-THREAD_SETMEM-THREAD_SETMEM_NC-for.patch --]
[-- Type: text/x-patch, Size: 5458 bytes --]

From 98ff24c0c7fba29c90ac37edd0057515aacdafa0 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Tue, 16 Mar 2021 07:41:46 -0700
Subject: [PATCH v6] x86_64: Correct THREAD_SETMEM/THREAD_SETMEM_NC for movq
 [BZ #27591]

config/i386/constraints.md in GCC has

(define_constraint "e"
  "32-bit signed integer constant, or a symbolic reference known
   to fit that range (for immediate operands in sign-extending x86-64
   instructions)."
  (match_operand 0 "x86_64_immediate_operand"))

Since movq takes a signed 32-bit immediate or a register source operand,
use "er", instead of "nr"/"ir", constraint for 32-bit signed integer
constant or register on movq.
---
 sysdeps/x86_64/Makefile           |  2 +
 sysdeps/x86_64/nptl/tls.h         | 10 ++++-
 sysdeps/x86_64/tst-x86-64-tls-1.c | 64 +++++++++++++++++++++++++++++++
 3 files changed, 74 insertions(+), 2 deletions(-)
 create mode 100644 sysdeps/x86_64/tst-x86-64-tls-1.c

diff --git a/sysdeps/x86_64/Makefile b/sysdeps/x86_64/Makefile
index d1d7cb9d2e..06a444b6af 100644
--- a/sysdeps/x86_64/Makefile
+++ b/sysdeps/x86_64/Makefile
@@ -183,6 +183,8 @@ ifeq (no,$(build-hardcoded-path-in-tests))
 tests-container += tst-glibc-hwcaps-cache
 endif
 
+tests-internal += tst-x86-64-tls-1
+
 endif # $(subdir) == elf
 
 ifeq ($(subdir),csu)
diff --git a/sysdeps/x86_64/nptl/tls.h b/sysdeps/x86_64/nptl/tls.h
index 20f0958780..a78c4f4d01 100644
--- a/sysdeps/x86_64/nptl/tls.h
+++ b/sysdeps/x86_64/nptl/tls.h
@@ -271,8 +271,11 @@ _Static_assert (offsetof (tcbhead_t, __glibc_unused2) == 0x80,
 		       "i" (offsetof (struct pthread, member)));	      \
      else /* 8 */							      \
        {								      \
+	 /* Since movq takes a signed 32-bit immediate or a register source   \
+	    operand, use "er" constraint for 32-bit signed integer constant   \
+	    or register.  */						      \
 	 asm volatile ("movq %q0,%%fs:%P1" :				      \
-		       : IMM_MODE ((uint64_t) cast_to_integer (value)),	      \
+		       : "er" ((uint64_t) cast_to_integer (value)),	      \
 			 "i" (offsetof (struct pthread, member)));	      \
        }})
 
@@ -296,8 +299,11 @@ _Static_assert (offsetof (tcbhead_t, __glibc_unused2) == 0x80,
 		       "r" (idx));					      \
      else /* 8 */							      \
        {								      \
+	 /* Since movq takes a signed 32-bit immediate or a register source   \
+	    operand, use "er" constraint for 32-bit signed integer constant   \
+	    or register.  */						      \
 	 asm volatile ("movq %q0,%%fs:%P1(,%q2,8)" :			      \
-		       : IMM_MODE ((uint64_t) cast_to_integer (value)),	      \
+		       : "er" ((uint64_t) cast_to_integer (value)),	      \
 			 "i" (offsetof (struct pthread, member[0])),	      \
 			 "r" (idx));					      \
        }})
diff --git a/sysdeps/x86_64/tst-x86-64-tls-1.c b/sysdeps/x86_64/tst-x86-64-tls-1.c
new file mode 100644
index 0000000000..354635884e
--- /dev/null
+++ b/sysdeps/x86_64/tst-x86-64-tls-1.c
@@ -0,0 +1,64 @@
+/* Test THREAD_SETMEM and THREAD_SETMEM_NC for IMM64.
+   Copyright (C) 2021 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 <tls.h>
+#include <support/check.h>
+
+static int
+do_test (void)
+{
+  unsigned long long int saved_ssp_base, ssp_base;
+  saved_ssp_base = THREAD_GETMEM (THREAD_SELF, header.ssp_base);
+
+  THREAD_SETMEM (THREAD_SELF, header.ssp_base, (1ULL << 57) - 1);
+  ssp_base = THREAD_GETMEM (THREAD_SELF, header.ssp_base);
+  if (ssp_base != ((1ULL << 57) - 1))
+    FAIL_EXIT1 ("THREAD_SETMEM: 0x%llx != 0x%llx",
+		ssp_base, (1ULL << 57) - 1);
+
+  THREAD_SETMEM (THREAD_SELF, header.ssp_base, -1ULL);
+  ssp_base = THREAD_GETMEM (THREAD_SELF, header.ssp_base);
+  if (ssp_base != -1ULL)
+    FAIL_EXIT1 ("THREAD_SETMEM: 0x%llx != 0x%llx", ssp_base, -1ULL);
+
+  THREAD_SETMEM (THREAD_SELF, header.ssp_base, saved_ssp_base);
+#ifndef __ILP32__
+  struct pthread_key_data *saved_specific, *specific;
+  saved_specific = THREAD_GETMEM_NC (THREAD_SELF, specific, 1);
+
+  uintptr_t value = (1UL << 57) - 1;
+  THREAD_SETMEM_NC (THREAD_SELF, specific, 1,
+		    (struct pthread_key_data *) value);
+  specific = THREAD_GETMEM_NC (THREAD_SELF, specific, 1);
+  if (specific != (struct pthread_key_data *) value)
+    FAIL_EXIT1 ("THREAD_GETMEM_NC: %p != %p",
+		specific, (struct pthread_key_data *) value);
+
+  THREAD_SETMEM_NC (THREAD_SELF, specific, 1,
+		    (struct pthread_key_data *) -1UL);
+  specific = THREAD_GETMEM_NC (THREAD_SELF, specific, 1);
+  if (specific != (struct pthread_key_data *) -1UL)
+    FAIL_EXIT1 ("THREAD_GETMEM_NC: %p != %p",
+		specific, (struct pthread_key_data *) -1UL);
+
+  THREAD_SETMEM_NC (THREAD_SELF, specific, 1, saved_specific);
+#endif
+  return 0;
+}
+
+#include <support/test-driver.c>
-- 
2.30.2


^ permalink raw reply	[flat|nested] 4+ messages in thread

* [PATCH v6] x86_64: Correct THREAD_SETMEM/THREAD_SETMEM_NC for movq [BZ #27591]
  2021-03-16 16:34                       ` Carlos O'Donell
@ 2021-03-16 16:50                         ` H.J. Lu
  2021-03-16 16:52                           ` H.J. Lu
  0 siblings, 1 reply; 4+ messages in thread
From: H.J. Lu @ 2021-03-16 16:50 UTC (permalink / raw)
  To: Carlos O'Donell
  Cc: Florian Weimer, Andreas Schwab, Carlos O'Donell via Libc-alpha

On Tue, Mar 16, 2021 at 9:34 AM Carlos O'Donell <carlos@redhat.com> wrote:
>
> On 3/16/21 12:10 PM, Florian Weimer via Libc-alpha wrote:
> > * Andreas Schwab:
> >
> >> I don't think this will work in general.  Wouldn't it be possible that
> >> an operands optimizes to a 64-bit constant in later passes?  What you
> >> really need is a constraint that only matches a 32-bit immediate or a
> >> register.  Like "rWf"?

config/i386/constraints.md in GCC has

(define_constraint "e"
  "32-bit signed integer constant, or a symbolic reference known
   to fit that range (for immediate operands in sign-extending x86-64
   instructions)."
  (match_operand 0 "x86_64_immediate_operand"))

"er" is the correct constraint for movq.

> > Maybe we should to the __seg_fs namespace instead?  Wouldn't that avoid
> > these issues?
>
> It might.
>
> HJ, Does it work to rewrite this using __seg_fs?

I tried it.  GCC generates worse code.

> Otherwise I'll review v5, which I think is better than it was before and
> makes forward progress.

Here is the v6 patch to use the "er" constraint.   OK for master?

Thanks.


-- 
H.J.

^ permalink raw reply	[flat|nested] 4+ messages in thread

end of thread, other threads:[~2021-04-01 13:51 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-03-19 18:35 [PATCH v6] x86_64: Correct THREAD_SETMEM/THREAD_SETMEM_NC for movq [BZ #27591] H.J. Lu
2021-04-01 13:51 ` Carlos O'Donell
  -- strict thread matches above, loose matches on Subject: below --
2021-02-02 19:12 [PATCH] x86_64: Update THREAD_SETMEM/THREAD_SETMEM_NC for IMM64 H.J. Lu
2021-03-01 13:30 ` Carlos O'Donell
2021-03-02 14:21   ` [PATCH v2] " H.J. Lu
2021-03-08 22:28     ` Carlos O'Donell
2021-03-09  0:09       ` [PATCH v3] " H.J. Lu
2021-03-15 12:49         ` Carlos O'Donell
2021-03-15 13:29           ` [PATCH v4] " H.J. Lu
2021-03-16  3:01             ` Carlos O'Donell
2021-03-16  9:04               ` Andreas Schwab
2021-03-16 15:45                 ` [PATCH v5] x86_64: Update THREAD_SETMEM/THREAD_SETMEM_NC for IMM64 [BZ #27591] H.J. Lu
2021-03-16 16:02                   ` Andreas Schwab
2021-03-16 16:10                     ` Florian Weimer
2021-03-16 16:34                       ` Carlos O'Donell
2021-03-16 16:50                         ` [PATCH v6] x86_64: Correct THREAD_SETMEM/THREAD_SETMEM_NC for movq " H.J. Lu
2021-03-16 16:52                           ` H.J. Lu

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