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Convert COPY instructions into KILLs if they have implicit defs.

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MachineCopyPropagation doesn't understand super-register liveness well
enough to be able to remove implicit defs of super-registers.

This fixes a problem in ARM/2012-01-26-CopyPropKills.ll that is exposed
by an future TwoAddressInstructionPass change. The KILL instructions are
removed before the machine code is emitted.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@169060 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen 2012-11-30 23:53:00 +00:00
parent a3959b6d69
commit 3e77747eba
1 changed files with 17 additions and 3 deletions
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20
lib/CodeGen/MachineCopyPropagation.cpp
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@ -17,6 +17,7 @@
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
@ -32,6 +33,7 @@ STATISTIC(NumDeletes, "Number of dead copies deleted");
namespace {
class MachineCopyPropagation : public MachineFunctionPass {
const TargetRegisterInfo *TRI;
const TargetInstrInfo *TII;
MachineRegisterInfo *MRI;
public:
@ -50,6 +52,7 @@ namespace {
SourceMap &SrcMap,
DenseMap<unsigned, MachineInstr*> &AvailCopyMap);
bool CopyPropagateBlock(MachineBasicBlock &MBB);
void removeCopy(MachineInstr *MI);
};
}
char MachineCopyPropagation::ID = 0;
@ -123,6 +126,16 @@ static bool isNopCopy(MachineInstr *CopyMI, unsigned Def, unsigned Src,
return false;
}
// Remove MI from the function because it has been determined it is dead.
// Turn it into a noop KILL instruction if it has super-register liveness
// adjustments.
void MachineCopyPropagation::removeCopy(MachineInstr *MI) {
if (MI->getNumOperands() == 2)
MI->eraseFromParent();
else
MI->setDesc(TII->get(TargetOpcode::KILL));
}
bool MachineCopyPropagation::CopyPropagateBlock(MachineBasicBlock &MBB) {
SmallSetVector<MachineInstr*, 8> MaybeDeadCopies; // Candidates for deletion
DenseMap<unsigned, MachineInstr*> AvailCopyMap; // Def -> available copies map
@ -168,7 +181,7 @@ bool MachineCopyPropagation::CopyPropagateBlock(MachineBasicBlock &MBB) {
for (MachineBasicBlock::iterator I = CopyMI, E = MI; I != E; ++I)
I->clearRegisterKills(Def, TRI);
MI->eraseFromParent();
removeCopy(MI);
Changed = true;
++NumDeletes;
continue;
@ -261,7 +274,7 @@ bool MachineCopyPropagation::CopyPropagateBlock(MachineBasicBlock &MBB) {
unsigned Reg = (*DI)->getOperand(0).getReg();
if (MRI->isReserved(Reg) || !MaskMO.clobbersPhysReg(Reg))
continue;
(*DI)->eraseFromParent();
removeCopy(*DI);
Changed = true;
++NumDeletes;
}
@ -297,7 +310,7 @@ bool MachineCopyPropagation::CopyPropagateBlock(MachineBasicBlock &MBB) {
DI = MaybeDeadCopies.begin(), DE = MaybeDeadCopies.end();
DI != DE; ++DI) {
if (!MRI->isReserved((*DI)->getOperand(0).getReg())) {
(*DI)->eraseFromParent();
removeCopy(*DI);
Changed = true;
++NumDeletes;
}
@ -311,6 +324,7 @@ bool MachineCopyPropagation::runOnMachineFunction(MachineFunction &MF) {
bool Changed = false;
TRI = MF.getTarget().getRegisterInfo();
TII = MF.getTarget().getInstrInfo();
MRI = &MF.getRegInfo();
for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)