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Ignore PHI-defs for -new-coalescer interference checks.

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A PHI can't create interference on its own. If two live ranges interfere
at a PHI, they must also interfere when leaving one of the PHI
predecessors.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@164330 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen
2012-09-20 23:08:42 +00:00
parent 2df8ac84ae
commit e6e2d8cd90
2 changed files with 56 additions and 4 deletions
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12
lib/CodeGen/RegisterCoalescer.cpp
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@@ -1402,7 +1402,6 @@ JoinVals::analyzeValue(unsigned ValNo, JoinVals &Other) {
// values should be merged into one, but not into any preceding value.
// The first value defined or visited gets CR_Keep, the other gets CR_Merge.
if (VNInfo *OtherVNI = OtherLRQ.valueDefined()) {
DEBUG(dbgs() << "\t\tDouble def: " << VNI->def << '\n');
assert(SlotIndex::isSameInstr(VNI->def, OtherVNI->def) && "Broken LRQ");
// One value stays, the other is merged. Keep the earlier one, or the first
@@ -1420,7 +1419,11 @@ JoinVals::analyzeValue(unsigned ValNo, JoinVals &Other) {
// Keep this value, check for conflicts when analyzing OtherVNI.
if (!OtherV.isAnalyzed())
return CR_Keep;
// Both sides have been analyzed now. Do they conflict?
// Both sides have been analyzed now.
// Allow overlapping PHI values. Any real interference would show up in a
// predecessor, the PHI itself can't introduce any conflicts.
if (VNI->isPHIDef())
return CR_Merge;
if (V.ValidLanes & OtherV.ValidLanes)
// Overlapping lanes can't be resolved.
return CR_Impossible;
@@ -1441,9 +1444,10 @@ JoinVals::analyzeValue(unsigned ValNo, JoinVals &Other) {
Other.computeAssignment(V.OtherVNI->id, *this);
const Val &OtherV = Other.Vals[V.OtherVNI->id];
// Don't attempt resolving PHI values for now.
// Allow overlapping PHI values. Any real interference would show up in a
// predecessor, the PHI itself can't introduce any conflicts.
if (VNI->isPHIDef())
return CR_Impossible;
return CR_Replace;
// Check for simple erasable conflicts.
if (DefMI->isImplicitDef())