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[SystemZ] Remove no-op MVCs

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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.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185705 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Richard Sandiford
2013-07-05 14:38:48 +00:00
parent e684b96e3c
commit 71804149a3
5 changed files with 134 additions and 1 deletions
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25
lib/Target/SystemZ/SystemZInstrInfo.cpp
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@@ -104,6 +104,31 @@ unsigned SystemZInstrInfo::isStoreToStackSlot(const MachineInstr *MI,
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,