diff options
| -rw-r--r-- | lib/Target/X86/X86ISelLowering.cpp | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp index 75fbd4490a..2e9dce36f1 100644 --- a/lib/Target/X86/X86ISelLowering.cpp +++ b/lib/Target/X86/X86ISelLowering.cpp @@ -3754,7 +3754,8 @@ SDOperand X86TargetLowering::LowerMEMSET(SDOperand Op, SelectionDAG &DAG) { ConstantSDNode *I = dyn_cast<ConstantSDNode>(Op.getOperand(3)); // If not DWORD aligned or size is more than the threshold, call memset. - // It knows how to align to the right boundary first. + // The libc version is likely to be faster for these cases. It can use the + // address value and run time information about the CPU. if ((Align & 3) != 0 || (I && I->getValue() > Subtarget->getMinRepStrSizeThreshold())) { MVT::ValueType IntPtr = getPointerTy(); @@ -3910,7 +3911,9 @@ SDOperand X86TargetLowering::LowerMEMCPY(SDOperand Op, SelectionDAG &DAG) { ConstantSDNode *I = dyn_cast<ConstantSDNode>(Op.getOperand(3)); // If not DWORD aligned or size is more than the threshold, call memcpy. - // It knows how to align to the right boundary first. + // The libc version is likely to be faster for these cases. It can use the + // address value and run time information about the CPU. + // With glibc 2.6.1 on a core 2, coping an array of 100M longs was 30% faster if ((Align & 3) != 0 || (I && I->getValue() > Subtarget->getMinRepStrSizeThreshold())) { MVT::ValueType IntPtr = getPointerTy(); |