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Better handle instructions that re-def a scratch register
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@84657 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -778,6 +778,8 @@ void PEI::scavengeFrameVirtualRegs(MachineFunction &Fn) {
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// directly.
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for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) {
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MachineInstr *MI = I;
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bool isDefInsn = false;
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bool isKillInsn = false;
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for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i)
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if (MI->getOperand(i).isReg()) {
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MachineOperand &MO = MI->getOperand(i);
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@ -802,6 +804,12 @@ void PEI::scavengeFrameVirtualRegs(MachineFunction &Fn) {
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}
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continue;
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}
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// If this is a def, remember that this insn defines the value.
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// This lets us properly consider insns which re-use the scratch
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// register, such as r2 = sub r2, #imm, in the middle of the
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// scratch range.
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if (MO.isDef())
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isDefInsn = true;
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// Have we already allocated a scratch register for this virtual?
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if (Reg != CurrentVirtReg) {
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@ -866,19 +874,20 @@ void PEI::scavengeFrameVirtualRegs(MachineFunction &Fn) {
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assert (CurrentScratchReg && "Missing scratch register!");
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MI->getOperand(i).setReg(CurrentScratchReg);
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// If this is the last use of the register, stop tracking it.
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if (MI->getOperand(i).isKill()) {
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PrevScratchReg = CurrentScratchReg;
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PrevLastUseMI = MI;
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isKillInsn = true;
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PrevLastUseOp = i;
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CurrentScratchReg = CurrentVirtReg = 0;
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havePrevValue = trackingCurrentValue;
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// Re-scan the operands of this instruction to catch definitions
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// of the scratch register we're using. This is to handle things
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// like ldr "r2, [scratch]" where scratch is r2.
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i = 0;
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PrevLastUseMI = MI;
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}
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}
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// If this is the last use of the scratch, stop tracking it. The
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// last use will be a kill operand in an instruction that does
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// not also define the scratch register.
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if (isKillInsn && !isDefInsn) {
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PrevScratchReg = CurrentScratchReg;
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CurrentScratchReg = CurrentVirtReg = 0;
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havePrevValue = trackingCurrentValue;
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}
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RS->forward(MI);
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}
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}
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