[PATCH] D112004: [SystemZ] Improve codegen for memset

[Jonas Paulsson via Phabricator via llvm-commits]

jonpa updated this revision to Diff 384702.
jonpa added a comment.

Patch updated per suggenstion.

I tried to also avoid folding just Dest so that two registers would not be used when SrcDisp is 4095, like:

  +  auto foldDisplIfNeeded = [&](MachineOperand &Base, uint64_t &Disp,
  +                               bool Force = false) -> void {
  +    if (Disp > 0xfff || Force) {
  ...
  +      if (DestDisp > 0xfff) {
  +        // Make sure only one base register is used.
  +        foldDisplIfNeeded(SrcBase, SrcDisp, true/*Force*/);
  +        DestBase = SrcBase;
  +        DestDisp = 1;
  +      }

This however did not change benchmarks at all, so I removed it (it did however improve memset-01.ll:f17,f18...). I also tried generalizing this idea to all operations, but again there was no cases of this in benchmarks.

Also some other minor fixing:

- Changed the variable names in insertMemMemOp() to avoid using the same names already used (DestBase, SrcBase, ...)
- add ByteMO directly also with STC in insertMemMemOp() and make sure to call earlyUseOperand() to clear any kill flag.
- For the PFD I decided it was simplest to subtract IsMemset compared to using both ThisSrcReg and SrcDisp.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D112004/new/

https://reviews.llvm.org/D112004

Files:
  llvm/lib/Target/SystemZ/SystemZISelLowering.cpp
  llvm/lib/Target/SystemZ/SystemZISelLowering.h
  llvm/lib/Target/SystemZ/SystemZInstrFormats.td
  llvm/lib/Target/SystemZ/SystemZInstrInfo.td
  llvm/lib/Target/SystemZ/SystemZOperators.td
  llvm/lib/Target/SystemZ/SystemZSelectionDAGInfo.cpp
  llvm/test/CodeGen/SystemZ/memset-01.ll
  llvm/test/CodeGen/SystemZ/memset-02.ll
  llvm/test/CodeGen/SystemZ/memset-04.ll
  llvm/test/CodeGen/SystemZ/memset-07.ll
  llvm/test/CodeGen/SystemZ/tail-call-mem-intrinsics.ll

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