[PATCH] D150600: [Lanai] Use backwards scavenging in frame index elimination

[Jay Foad via Phabricator via llvm-commits]

foad created this revision.
foad added a reviewer: jpienaar.
Herald added subscribers: StephenFan, arphaman, hiraditya.
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Herald added a project: LLVM.
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This is preferred because it does not rely on accurate kill flags.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D150600

Files:
  llvm/lib/Target/Lanai/LanaiRegisterInfo.cpp
  llvm/lib/Target/Lanai/LanaiRegisterInfo.h


Index: llvm/lib/Target/Lanai/LanaiRegisterInfo.h
===================================================================
--- llvm/lib/Target/Lanai/LanaiRegisterInfo.h
+++ llvm/lib/Target/Lanai/LanaiRegisterInfo.h
@@ -34,6 +34,8 @@
 
   bool requiresRegisterScavenging(const MachineFunction &MF) const override;
 
+  bool supportsBackwardScavenger() const override { return true; }
+
   bool eliminateFrameIndex(MachineBasicBlock::iterator II, int SPAdj,
                            unsigned FIOperandNum,
                            RegScavenger *RS = nullptr) const override;
Index: llvm/lib/Target/Lanai/LanaiRegisterInfo.cpp
===================================================================
--- llvm/lib/Target/Lanai/LanaiRegisterInfo.cpp
+++ llvm/lib/Target/Lanai/LanaiRegisterInfo.cpp
@@ -235,10 +235,11 @@
         .addReg(FrameReg)
         .addImm(-Offset);
     MI.eraseFromParent();
-  } else {
-    MI.getOperand(FIOperandNum).ChangeToRegister(FrameReg, /*isDef=*/false);
-    MI.getOperand(FIOperandNum + 1).ChangeToImmediate(Offset);
+    return true;
   }
+
+  MI.getOperand(FIOperandNum).ChangeToRegister(FrameReg, /*isDef=*/false);
+  MI.getOperand(FIOperandNum + 1).ChangeToImmediate(Offset);
   return false;
 }
 


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