The CMPXCHG instruction has the following operands: - AX (implicit, CompareValue): input and output - destination operand (*Value): input and output - source operand (ExchangeValue): input
The IA32 version of InternalSyncCompareExchange16() correctly marks CompareValue as input/output, but it marks (*Value) only as input. The X64 version of InternalSyncCompareExchange16() attempts to mark both CompareValue and (*Value) as input/output, but it doesn't use the appropriate constraints for either operand. Fix these issues. Furthermore, prefer the short "+" constraint for I/O operands over the <output-operand-number> constraint that can be applied to the input instances of I/O operands. Cc: Liming Gao <liming....@intel.com> Cc: Michael D Kinney <michael.d.kin...@intel.com> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1208 Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Laszlo Ersek <ler...@redhat.com> --- MdePkg/Library/BaseSynchronizationLib/Ia32/GccInline.c | 9 ++++----- MdePkg/Library/BaseSynchronizationLib/X64/GccInline.c | 10 ++++------ 2 files changed, 8 insertions(+), 11 deletions(-) diff --git a/MdePkg/Library/BaseSynchronizationLib/Ia32/GccInline.c b/MdePkg/Library/BaseSynchronizationLib/Ia32/GccInline.c index 1976720ac636..bd98a5aebfe7 100644 --- a/MdePkg/Library/BaseSynchronizationLib/Ia32/GccInline.c +++ b/MdePkg/Library/BaseSynchronizationLib/Ia32/GccInline.c @@ -115,11 +115,10 @@ InternalSyncCompareExchange16 ( { __asm__ __volatile__ ( "lock \n\t" - "cmpxchgw %1, %2 \n\t" - : "=a" (CompareValue) // %0 - : "q" (ExchangeValue), // %1 - "m" (*Value), // %2 - "0" (CompareValue) // %3 + "cmpxchgw %2, %1 \n\t" + : "+a" (CompareValue), // %0 + "+m" (*Value) // %1 + : "q" (ExchangeValue) // %2 : "memory", "cc" ); diff --git a/MdePkg/Library/BaseSynchronizationLib/X64/GccInline.c b/MdePkg/Library/BaseSynchronizationLib/X64/GccInline.c index 0212798d7a27..4338fb8e65e8 100644 --- a/MdePkg/Library/BaseSynchronizationLib/X64/GccInline.c +++ b/MdePkg/Library/BaseSynchronizationLib/X64/GccInline.c @@ -115,12 +115,10 @@ InternalSyncCompareExchange16 ( { __asm__ __volatile__ ( "lock \n\t" - "cmpxchgw %3, %1 \n\t" - : "=a" (CompareValue), // %0 - "=m" (*Value) // %1 - : "a" (CompareValue), // %2 - "r" (ExchangeValue), // %3 - "m" (*Value) // %4 + "cmpxchgw %2, %1 \n\t" + : "+a" (CompareValue), // %0 + "+m" (*Value) // %1 + : "r" (ExchangeValue) // %2 : "memory", "cc" ); -- 2.14.1.3.gb7cf6e02401b _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
