[compiler-rt] r274634 - [asan Win64] Implement atomic_compare_exchange_strong for 8 bit

[David Majnemer via llvm-commits]

On Wed, Jul 6, 2016 at 9:33 AM, Etienne Bergeron via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

> Author: etienneb
> Date: Wed Jul  6 11:33:57 2016
> New Revision: 274634
>
> URL: http://llvm.org/viewvc/llvm-project?rev=274634&view=rev
> Log:
> [asan Win64] Implement atomic_compare_exchange_strong for 8 bit
>
> Patch by: Wei Wang
> Differential Revision: http://reviews.llvm.org/D21950
>
>
> Modified:
>     compiler-rt/trunk/lib/sanitizer_common/sanitizer_atomic_msvc.h
>
> Modified: compiler-rt/trunk/lib/sanitizer_common/sanitizer_atomic_msvc.h
> URL:
> http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/sanitizer_common/sanitizer_atomic_msvc.h?rev=274634&r1=274633&r2=274634&view=diff
>
> ==============================================================================
> --- compiler-rt/trunk/lib/sanitizer_common/sanitizer_atomic_msvc.h
> (original)
> +++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_atomic_msvc.h Wed
> Jul  6 11:33:57 2016
> @@ -33,6 +33,10 @@ extern "C" long _InterlockedExchange(
>  extern "C" long _InterlockedExchangeAdd(  // NOLINT
>      long volatile * Addend, long Value);  // NOLINT
>  #pragma intrinsic(_InterlockedExchangeAdd)
> +extern "C" char _InterlockedCompareExchange8(  // NOLINT
> +    char volatile *Destination,                // NOLINT
> +    char Exchange, char Comparand);            // NOLINT
> +#pragma intrinsic(_InterlockedCompareExchange8)
>  extern "C" short _InterlockedCompareExchange16(  // NOLINT
>      short volatile *Destination,                 // NOLINT
>      short Exchange, short Comparand);            // NOLINT
> @@ -175,15 +179,13 @@ INLINE bool atomic_compare_exchange_stro
>                                             u8 *cmp,
>                                             u8 xchgv,
>                                             memory_order mo) {
> -#ifdef _WIN64
> -  // TODO(wwchrome): Implement same functionality without inline asm.
> -  // Inline asm not supported in Win64.
> -  __debugbreak();
> -  return false;
> -#else
>    (void)mo;
>    DCHECK(!((uptr)a % sizeof(*a)));
>    u8 cmpv = *cmp;
> +#ifdef _WIN64
> +  u8 prev = (u8)_InterlockedCompareExchange8(
> +      (volatile char*)&a->val_dont_use, (char)xchgv, (char)cmpv);
> +#else
>    u8 prev;
>    __asm {
>      mov al, cmpv
> @@ -192,11 +194,11 @@ INLINE bool atomic_compare_exchange_stro
>      lock cmpxchg [ecx], dl
>      mov prev, al
>    }
>

Could we have used _InterlockedCompareExchange8 on the #else path as well?


> +#endif
>    if (prev == cmpv)
>      return true;
>    *cmp = prev;
>    return false;
> -#endif
>  }
>
>  INLINE bool atomic_compare_exchange_strong(volatile atomic_uintptr_t *a,
>
>
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