[SystemZ] Remove no-op MVCs
The stack coloring pass has code to delete stores and loads that become
trivially dead after coloring. Extend it to cope with single instructions
that copy from one frame index to another.
The testcase happens to show an example of this kicking in at the moment.
It did occur in Real Code too though.
llvm-svn: 185705
diff --git a/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp b/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp
index 81d72e0..cfd270a 100644
--- a/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp
@@ -104,6 +104,31 @@
return isSimpleMove(MI, FrameIndex, SystemZII::SimpleBDXStore);
}
+bool SystemZInstrInfo::isStackSlotCopy(const MachineInstr *MI,
+ int &DestFrameIndex,
+ int &SrcFrameIndex) const {
+ // Check for MVC 0(Length,FI1),0(FI2)
+ const MachineFrameInfo *MFI = MI->getParent()->getParent()->getFrameInfo();
+ if (MI->getOpcode() != SystemZ::MVC ||
+ !MI->getOperand(0).isFI() ||
+ MI->getOperand(1).getImm() != 0 ||
+ !MI->getOperand(3).isFI() ||
+ MI->getOperand(4).getImm() != 0)
+ return false;
+
+ // Check that Length covers the full slots.
+ int64_t Length = MI->getOperand(2).getImm();
+ unsigned FI1 = MI->getOperand(0).getIndex();
+ unsigned FI2 = MI->getOperand(3).getIndex();
+ if (MFI->getObjectSize(FI1) != Length ||
+ MFI->getObjectSize(FI2) != Length)
+ return false;
+
+ DestFrameIndex = FI1;
+ SrcFrameIndex = FI2;
+ return true;
+}
+
bool SystemZInstrInfo::AnalyzeBranch(MachineBasicBlock &MBB,
MachineBasicBlock *&TBB,
MachineBasicBlock *&FBB,