[PATCH] D154193: [X86]Remove TEST in AND32ri+TEST16rr in peephole-opt

[Craig Topper via Phabricator via llvm-commits]

craig.topper added inline comments.


================
Comment at: llvm/lib/Target/X86/X86InstrInfo.cpp:1007
+           VregDefInstr->getOpcode() == X86::AND64ri32) &&
+          isInt<16>(VregDefInstr->getOperand(2).getImm())))
+      return false;
----------------
XinWang10 wrote:
> craig.topper wrote:
> > Doesn't it need to be isUint<16>?
> > 
> > Bit 15 would also need to be 0 if the sign flag is being used.
> Yes, It should be.
Do we have a test where we use the sign flag? The AND would set the sign flag based on bit 31. the TEST16rr would set the sign flag based on bit 15. So we could only do the transform if bit 31 and bit 15 are known to be zero (bit 31 is handled by the isUint<16> check. Or we need to not be using the sign flag from the test.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D154193/new/

https://reviews.llvm.org/D154193