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Re: [Qemu-devel] testandset asm fix
From: |
Piotras |
Subject: |
Re: [Qemu-devel] testandset asm fix |
Date: |
Mon, 7 Feb 2005 13:03:22 +0000 |
m68k has similar problem
http://lists.gnu.org/archive/html/qemu-devel/2004-08/msg00122.html
Regards,
Piotrek
On Sun, 6 Feb 2005 14:43:38 +0000, Paul Brook <address@hidden> wrote:
> The inline assembly used for the x86/x86-64 host testandset routine is bogus.
> The operand constraints are wrong (Fails to compile at -O0).
> Also the return value is incorrect. It should return 0 if the lock was
> successfully acquired.
>
> Patch below fixes it. The additional sete test is unnecessary, we can just use
> the comparison/writeback value.
>
> Paul
>
> Index: exec-all.h
> ===================================================================
> RCS file: /cvsroot/qemu/qemu/exec-all.h,v
> retrieving revision 1.26
> diff -u -p -r1.26 exec-all.h
> --- exec-all.h 10 Jan 2005 23:23:48 -0000 1.26
> +++ exec-all.h 6 Feb 2005 14:35:43 -0000
> @@ -392,28 +392,24 @@ static inline int testandset (int *p)
> #ifdef __i386__
> static inline int testandset (int *p)
> {
> - char ret;
> - long int readval;
> -
> - __asm__ __volatile__ ("lock; cmpxchgl %3, %1; sete %0"
> - : "=q" (ret), "=m" (*p), "=a" (readval)
> - : "r" (1), "m" (*p), "a" (0)
> - : "memory");
> - return ret;
> + long int readval = 0;
> +
> + __asm__ __volatile__ ("lock; cmpxchgl %2, %0"
> + : "+m" (*p), "+a" (readval)
> + : "r" (1));
> + return readval;
> }
> #endif
>
> #ifdef __x86_64__
> static inline int testandset (int *p)
> {
> - char ret;
> - int readval;
> -
> - __asm__ __volatile__ ("lock; cmpxchgl %3, %1; sete %0"
> - : "=q" (ret), "=m" (*p), "=a" (readval)
> - : "r" (1), "m" (*p), "a" (0)
> - : "memory");
> - return ret;
> + long int readval = 0;
> +
> + __asm__ __volatile__ ("lock; cmpxchgl %2, %0"
> + : "+m" (*p), "+a" (readval)
> + : "r" (1));
> + return readval;
> }
> #endif
>
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