RegisterCoalescer: Do not remove IMPLICIT_DEFS if they are required for subranges.
The register coalescer used to remove implicit_defs when they are covered by the main range anyway. With subreg liveness tracking we can't do that anymore in places where the IMPLICIT_DEF is required as begin of a subregister liverange. llvm-svn: 225416
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@ -1912,8 +1912,14 @@ JoinVals::analyzeValue(unsigned ValNo, JoinVals &Other) {
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return CR_Replace;
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// Check for simple erasable conflicts.
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if (DefMI->isImplicitDef())
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if (DefMI->isImplicitDef()) {
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// We need the def for the subregister if there is nothing else live at the
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// subrange at this point.
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if (TrackSubRegLiveness
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&& (V.WriteLanes & (OtherV.ValidLanes | OtherV.WriteLanes)) == 0)
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return CR_Replace;
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return CR_Erase;
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}
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// Include the non-conflict where DefMI is a coalescable copy that kills
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// OtherVNI. We still want the copy erased and value numbers merged.
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