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Re: [Bug inline-asm/23242] New: Invalid %sil register chosen when dereferenced pointer used in inline asm with -O0

From: Andrew Pinski <pinskia at physics dot uc dot edu>
To: gcc-bugzilla at gcc dot gnu dot org
Cc: ianw at gelato dot unsw dot edu dot au, "gcc-bugs at gcc dot gnu dot org BUGS" <gcc-bugs at gcc dot gnu dot org>
Date: Thu, 4 Aug 2005 21:14:04 -0400
Subject: Re: [Bug inline-asm/23242] New: Invalid %sil register chosen when dereferenced pointer used in inline asm with -O0
References: <20050805003204.23242.ianw@gelato.unsw.edu.au>

On Aug 4, 2005, at 8:32 PM, ianw at gelato dot unsw dot edu dot au wrote:

  /* this one doesn't */
    __asm__ __volatile__("xchgb %0, %1"
  : "=r"(old), "=m"(*newp)
  : "0"(0xff), "m"(*newp) : "memory");

This is not a bug.

r is selecting %sil which is a valid register for x86_64.

"r" is assuming that it is a full size register.

Use "Q" instead.

-- Pinski

PS The reason why I am CC you instead of writing this into bugzilla is because bugzilla seems dead.

References:
- [Bug inline-asm/23242] New: Invalid %sil register chosen when dereferenced pointer used in inline asm with -O0
  - From: ianw at gelato dot unsw dot edu dot au

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