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Re: basic asm and memory clobbers

From: Jeff Law <law at redhat dot com>
To: Andrew Haley <aph at redhat dot com>, David Wohlferd <dw at LimeGreenSocks dot com>, Segher Boessenkool <segher at kernel dot crashing dot org>
Cc: "gcc at gcc dot gnu dot org" <gcc at gcc dot gnu dot org>, rth at gcc dot gnu dot org, pinskia at gcc dot gnu dot org, Sandra Loosemore <sandra at codesourcery dot com>
Date: Fri, 20 Nov 2015 09:40:56 -0700
Subject: Re: basic asm and memory clobbers
Authentication-results: sourceware.org; auth=none
References: <563FE459 dot 3000003 at LimeGreenSocks dot com> <20151109093229 dot GA5260 at gate dot crashing dot org> <56493010 dot 9070707 at LimeGreenSocks dot com> <564A4AA5 dot 1080706 at redhat dot com> <564AC155 dot 4040601 at LimeGreenSocks dot com> <564B9CB1 dot 1060001 at redhat dot com> <564E762B dot 6070705 at LimeGreenSocks dot com> <564EF338 dot 4030703 at redhat dot com> <564EF7FF dot 1070107 at LimeGreenSocks dot com> <564F008B dot 8040703 at redhat dot com>

On 11/20/2015 04:14 AM, Andrew Haley wrote:

On 20/11/15 10:37, David Wohlferd wrote:

The intent for 24414 is to change basic asm such that it will become
(quoting jeff) "an opaque blob that read/write/clobber any register or
memory location."  Such being the case, "memory" is not sufficient:

#define CLOBBERALL "eax", "ebx", "ecx", "edx", "r8", "r9", "r10", "r11",
"r12", "r13", "r14", "r15", "edi", "esi", "ebp", "cc", "memory"


Hmm.  I would not be at all surprised to see this cause reload
failures.  You certainly shouldn't clobber the frame pointer on
any machine which needs one.

Right. It'll cause other issues as well. It's the only reason why Ididn't change the code internally to stomp every hard register back in 1999.


jeff

References:
- basic asm and memory clobbers
  - From: David Wohlferd
- Re: basic asm and memory clobbers
  - From: Segher Boessenkool
- Re: basic asm and memory clobbers
  - From: David Wohlferd
- Re: basic asm and memory clobbers
  - From: Jeff Law
- Re: basic asm and memory clobbers
  - From: David Wohlferd
- Re: basic asm and memory clobbers
  - From: Jeff Law
- Re: basic asm and memory clobbers
  - From: David Wohlferd
- Re: basic asm and memory clobbers
  - From: Andrew Haley
- Re: basic asm and memory clobbers
  - From: David Wohlferd
- Re: basic asm and memory clobbers
  - From: Andrew Haley

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