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RegisterCoalescer: Do not remove IMPLICIT_DEFS if they are required for subranges.

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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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225416 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Matthias Braun 2015-01-08 00:21:23 +00:00
parent a065cf13cd
commit 9f6a38fc70
1 changed files with 7 additions and 1 deletions
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8
lib/CodeGen/RegisterCoalescer.cpp
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@ -1912,8 +1912,14 @@ JoinVals::analyzeValue(unsigned ValNo, JoinVals &Other) {
return CR_Replace; return CR_Replace;
// Check for simple erasable conflicts. // Check for simple erasable conflicts.
if (DefMI->isImplicitDef()) if (DefMI->isImplicitDef()) {
// We need the def for the subregister if there is nothing else live at the
// subrange at this point.
if (TrackSubRegLiveness
&& (V.WriteLanes & (OtherV.ValidLanes | OtherV.WriteLanes)) == 0)
return CR_Replace;
return CR_Erase; return CR_Erase;
}
// Include the non-conflict where DefMI is a coalescable copy that kills // Include the non-conflict where DefMI is a coalescable copy that kills
// OtherVNI. We still want the copy erased and value numbers merged. // OtherVNI. We still want the copy erased and value numbers merged.