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Extend -new-coalescer SSA update to handle mapped values as well.

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The old-fashioned many-to-one value mapping doesn't always work when
merging vector lanes. A value can map to multiple different values, and
it can even be necessary to insert new PHIs.

When a value number is defined by a copy from a value number that
required SSa update, include the live range of the copied value number
in the SSA update as well. It is not necessarily a copy of the original
value number any longer.

llvm-svn: 164329
This commit is contained in:
Jakob Stoklund Olesen 2012-09-20 23:08:39 +00:00
parent eb7dd83969
commit 32e4e26aa6
2 changed files with 62 additions and 9 deletions
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3
lib/CodeGen/LiveIntervalAnalysis.cpp
View File

@ -742,9 +742,6 @@ void LiveIntervals::extendToIndices(LiveInterval *LI,
void LiveIntervals::pruneValue(LiveInterval *LI, SlotIndex Kill,
SmallVectorImpl<SlotIndex> *EndPoints) {
LiveRangeQuery LRQ(*LI, Kill);
assert (!LRQ.valueDefined() && "Can't prune value at the defining instr");
// Also can't prune a value that isn't there.
VNInfo *VNI = LRQ.valueOut();
if (!VNI)
return;

68
lib/CodeGen/RegisterCoalescer.cpp
View File

@ -1246,8 +1246,15 @@ class JoinVals {
// Value in the other live range that overlaps this def, if any.
VNInfo *OtherVNI;
// True when the live range of this value will be pruned because of an
// overlapping CR_Replace value in the other live range.
bool Pruned;
// True once Pruned above has been computed.
bool PrunedComputed;
Val() : Resolution(CR_Keep), WriteLanes(0), ValidLanes(0),
RedefVNI(0), OtherVNI(0) {}
RedefVNI(0), OtherVNI(0), Pruned(false), PrunedComputed(false) {}
bool isAnalyzed() const { return WriteLanes != 0; }
};
@ -1262,6 +1269,7 @@ class JoinVals {
bool taintExtent(unsigned, unsigned, JoinVals&,
SmallVectorImpl<std::pair<SlotIndex, unsigned> >&);
bool usesLanes(MachineInstr *MI, unsigned, unsigned, unsigned);
bool isPrunedValue(unsigned ValNo, JoinVals &Other);
public:
JoinVals(LiveInterval &li, unsigned subIdx,
@ -1527,6 +1535,12 @@ void JoinVals::computeAssignment(unsigned ValNo, JoinVals &Other) {
<< V.OtherVNI->def << " --> @"
<< NewVNInfo[Assignments[ValNo]]->def << '\n');
break;
case CR_Replace:
case CR_Unresolved:
// The other value is going to be pruned if this join is successful.
assert(V.OtherVNI && "OtherVNI not assigned, can't prune");
Other.Vals[V.OtherVNI->id].Pruned = true;
// Fall through.
default:
// This value number needs to go in the final joined live range.
Assignments[ValNo] = NewVNInfo.size();
@ -1682,15 +1696,57 @@ bool JoinVals::resolveConflicts(JoinVals &Other) {
return true;
}
// Determine if ValNo is a copy of a value number in LI or Other.LI that will
// be pruned:
//
// %dst = COPY %src
// %src = COPY %dst <-- This value to be pruned.
// %dst = COPY %src <-- This value is a copy of a pruned value.
//
bool JoinVals::isPrunedValue(unsigned ValNo, JoinVals &Other) {
Val &V = Vals[ValNo];
if (V.Pruned || V.PrunedComputed)
return V.Pruned;
if (V.Resolution != CR_Erase && V.Resolution != CR_Merge)
return V.Pruned;
// Follow copies up the dominator tree and check if any intermediate value
// has been pruned.
V.PrunedComputed = true;
V.Pruned = Other.isPrunedValue(V.OtherVNI->id, *this);
return V.Pruned;
}
void JoinVals::pruneValues(JoinVals &Other,
SmallVectorImpl<SlotIndex> &EndPoints) {
for (unsigned i = 0, e = LI.getNumValNums(); i != e; ++i) {
if (Vals[i].Resolution != CR_Replace)
continue;
SlotIndex Def = LI.getValNumInfo(i)->def;
LIS->pruneValue(&Other.LI, Def, &EndPoints);
DEBUG(dbgs() << "\t\tpruned " << PrintReg(Other.LI.reg) << " at " << Def
<< ": " << Other.LI << '\n');
switch (Vals[i].Resolution) {
case CR_Keep:
break;
case CR_Replace:
// This value takes precedence over the value in Other.LI.
LIS->pruneValue(&Other.LI, Def, &EndPoints);
DEBUG(dbgs() << "\t\tpruned " << PrintReg(Other.LI.reg) << " at " << Def
<< ": " << Other.LI << '\n');
break;
case CR_Erase:
case CR_Merge:
if (isPrunedValue(i, Other)) {
// This value is ultimately a copy of a pruned value in LI or Other.LI.
// We can no longer trust the value mapping computed by
// computeAssignment(), the value that was originally copied could have
// been replaced.
LIS->pruneValue(&LI, Def, &EndPoints);
DEBUG(dbgs() << "\t\tpruned all of " << PrintReg(LI.reg) << " at "
<< Def << ": " << LI << '\n');
}
break;
case CR_Unresolved:
case CR_Impossible:
llvm_unreachable("Unresolved conflicts");
}
}
}