[PATCH] D139679: [X86] Don't zero out %eax if both %al and %ah are used

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added inline comments.


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Comment at: llvm/lib/Target/X86/X86FrameLowering.cpp:499-501
 void X86FrameLowering::emitZeroCallUsedRegs(BitVector RegsToZero,
                                             MachineBasicBlock &MBB) const {
   const MachineFunction &MF = *MBB.getParent();
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void wrote:
> arsenm wrote:
> > Why is this doing so much work? Why can't this use LivePhysRegUnits and addLiveOuts?
> Is there an example of how to use them?
Simplest looking one looks like DeadMachineInstructionElim. Just addLiveOuts and stepBackward to the point you want. Then check what's live


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D139679/new/

https://reviews.llvm.org/D139679