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Ignore IMPLICIT_DEF instructions when computing physreg liveness.
While they appear to provide a normal clobbering def, they don't in the case of the awkward IMPLICIT_DEF+INSERT_SUBREG idiom. It would be good to change INSERT_SUBREG; until then, this change allows post-regalloc scheduling to cope in a mildly conservative way. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60583 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -353,6 +353,13 @@ bool SchedulePostRATDList::BreakAntiDependencies() {
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I != E; ++I, --Count) {
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MachineInstr *MI = &*I;
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// After regalloc, IMPLICIT_DEF instructions aren't safe to treat as
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// dependence-breaking. In the case of an INSERT_SUBREG, the IMPLICIT_DEF
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// is left behind appearing to clobber the super-register, while the
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// subregister needs to remain live. So we just ignore them.
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if (MI->getOpcode() == TargetInstrInfo::IMPLICIT_DEF)
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continue;
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// Check if this instruction has an anti-dependence that we're
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// interested in.
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DenseMap<MachineInstr *, unsigned>::iterator C = CriticalAntiDeps.find(MI);
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