Remove move copies and dead stuff by not clobbering the result reg of a noop copy.
llvm-svn: 25926
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1318240fd0
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@ -607,6 +607,15 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, const VirtRegMap &VRM) {
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}
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if (!OpTakenCareOf) {
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// Check to see if this is a noop copy. If so, eliminate the
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// instruction before considering the dest reg to be changed.
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unsigned Src, Dst;
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if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
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++NumDCE;
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DEBUG(std::cerr << "Removing now-noop copy: " << MI);
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MBB.erase(&MI);
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goto ProcessNextInst;
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}
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ClobberPhysReg(VirtReg, SpillSlotsAvailable, PhysRegsAvailable);
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continue;
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}
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@ -631,6 +640,18 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, const VirtRegMap &VRM) {
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DEBUG(std::cerr << "Store:\t" << *next(MII));
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MI.SetMachineOperandReg(i, PhysReg);
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// Check to see if this is a noop copy. If so, eliminate the
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// instruction before considering the dest reg to be changed.
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{
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unsigned Src, Dst;
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if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
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++NumDCE;
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DEBUG(std::cerr << "Removing now-noop copy: " << MI);
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MBB.erase(&MI);
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goto ProcessNextInst;
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}
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}
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// If there is a dead store to this stack slot, nuke it now.
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MachineInstr *&LastStore = MaybeDeadStores[StackSlot];
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if (LastStore) {
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@ -654,18 +675,6 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, const VirtRegMap &VRM) {
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++NumStores;
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}
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}
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// Okay, the instruction has been completely processed, input and output
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// registers have been added. As a final sanity check, make sure this is
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// not a noop-copy. If it is, nuke it.
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{
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unsigned Src, Dst;
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if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
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++NumDCE;
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DEBUG(std::cerr << "Removing now-noop copy: " << MI);
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MBB.erase(&MI);
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}
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}
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ProcessNextInst:
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MII = NextMII;
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}
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