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If the only use of something is a DEBUG_VALUE, don't
let that stop it from being deleted, and change the DEBUG_VALUE value to undef. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@94694 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -107,6 +107,20 @@ bool DeadMachineInstructionElim::runOnMachineFunction(MachineFunction &MF) {
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MIE = MBB->rend(); MII != MIE; ) {
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MIE = MBB->rend(); MII != MIE; ) {
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MachineInstr *MI = &*MII;
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MachineInstr *MI = &*MII;
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if (MI->getOpcode()==TargetInstrInfo::DEBUG_VALUE) {
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// Don't delete the DEBUG_VALUE itself, but if its Value operand is
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// a vreg and this is the only use, substitute an undef operand;
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// the former operand will then be deleted normally.
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if (MI->getNumOperands()==3 && MI->getOperand(0).isReg()) {
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unsigned Reg = MI->getOperand(0).getReg();
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MachineRegisterInfo::use_iterator I = MRI->use_begin(Reg);
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assert(I != MRI->use_end());
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if (++I == MRI->use_end())
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// only one use, which must be this DEBUG_VALUE.
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MI->getOperand(0).setReg(0U);
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}
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}
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// If the instruction is dead, delete it!
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// If the instruction is dead, delete it!
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if (isDead(MI)) {
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if (isDead(MI)) {
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DEBUG(dbgs() << "DeadMachineInstructionElim: DELETING: " << *MI);
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DEBUG(dbgs() << "DeadMachineInstructionElim: DELETING: " << *MI);
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