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Only run the updateSSA loop when we have actually seen multiple values.

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When only a single value has been seen, new PHIDefs are never needed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126911 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen 2011-03-03 01:29:10 +00:00
parent c29d9b3495
commit 8701768ae2
1 changed files with 23 additions and 3 deletions
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26
lib/CodeGen/SplitKit.cpp
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@ -313,6 +313,10 @@ void SplitEditor::extendRange(unsigned RegIdx, SlotIndex Idx) {
SmallVector<MachineDomTreeNode*, 16> LiveIn;
LiveIn.push_back(MDT[IdxMBB]);
// Remember if we have seen more than one value.
bool UniqueVNI = true;
VNInfo *IdxVNI = 0;
// Using LiveOutCache as a visited set, perform a BFS for all reaching defs.
for (unsigned i = 0; i != LiveIn.size(); ++i) {
MachineBasicBlock *MBB = LiveIn[i]->getBlock();
@ -323,9 +327,14 @@ void SplitEditor::extendRange(unsigned RegIdx, SlotIndex Idx) {
std::pair<LiveOutMap::iterator,bool> LOIP =
LiveOutCache.insert(std::make_pair(Pred, LiveOutPair()));
// Yes, we have been here before.
if (!LOIP.second)
if (!LOIP.second) {
if (VNInfo *VNI = LOIP.first->second.first) {
if (IdxVNI && IdxVNI != VNI)
UniqueVNI = false;
IdxVNI = VNI;
}
continue;
}
// Does Pred provide a live-out value?
SlotIndex Start, Last;
tie(Start, Last) = LIS.getSlotIndexes()->getMBBRange(Pred);
@ -335,16 +344,27 @@ void SplitEditor::extendRange(unsigned RegIdx, SlotIndex Idx) {
LiveOutPair &LOP = LOIP.first->second;
LOP.first = VNI;
LOP.second = MDT[DefMBB];
if (IdxVNI && IdxVNI != VNI)
UniqueVNI = false;
IdxVNI = VNI;
continue;
}
// No, we need a live-in value for Pred as well
if (Pred != IdxMBB)
LiveIn.push_back(MDT[Pred]);
else
UniqueVNI = false; // Loopback to IdxMBB, ask updateSSA() for help.
}
}
// We may need to add phi-def values to preserve the SSA form.
VNInfo *IdxVNI = updateSSA(RegIdx, LiveIn, Idx, IdxMBB);
if (UniqueVNI) {
LiveOutPair LOP(IdxVNI, MDT[LIS.getMBBFromIndex(IdxVNI->def)]);
// Update LiveOutCache, but skip IdxMBB at LiveIn[0].
for (unsigned i = 1, e = LiveIn.size(); i != e; ++i)
LiveOutCache[LiveIn[i]->getBlock()] = LOP;
} else
IdxVNI = updateSSA(RegIdx, LiveIn, Idx, IdxMBB);
#ifndef NDEBUG
// Check the LiveOutCache invariants.