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Enhance LiveValues to work on PHI operands.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@67523 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2009-03-23 15:49:37 +00:00
parent b45088cd96
commit a9d71e1319
1 changed files with 25 additions and 14 deletions
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39
lib/Analysis/LiveValues.cpp
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@ -142,21 +142,32 @@ LiveValues::Memo &LiveValues::compute(const Value *V) {
if (L->contains(UseBB))
break;
if (isa<PHINode>(U)) {
// The value is used by a PHI, so it is live-out of the defining block.
LiveOutOfDefBB = true;
} else if (UseBB != DefBB) {
// A use outside the defining block has been found.
LiveOutOfDefBB = true;
// Search for live-through blocks.
const BasicBlock *BB;
if (const PHINode *PHI = dyn_cast<PHINode>(U)) {
// For PHI nodes, start the search at the incoming block paired with the
// incoming value, which must be dominated by the definition.
unsigned Num = PHI->getIncomingValueNumForOperand(I.getOperandNo());
BB = PHI->getIncomingBlock(Num);
// Climb the immediate dominator tree from the use to the definition
// and mark all intermediate blocks as live-through. Don't do this if
// the user is a PHI because such users may not be dominated by the
// definition.
for (const BasicBlock *BB = getImmediateDominator(UseBB, DT);
BB != DefBB; BB = getImmediateDominator(BB, DT))
if (!M.LiveThrough.insert(BB))
break;
// A PHI-node use means the value is live-out of it's defining block
// even if that block also contains the only use.
LiveOutOfDefBB = true;
} else {
// Otherwise just start the search at the use.
BB = UseBB;
// Note if the use is outside the defining block.
LiveOutOfDefBB |= UseBB != DefBB;
}
// Climb the immediate dominator tree from the use to the definition
// and mark all intermediate blocks as live-through. Don't do this if
// the user is a PHI because such users may not be dominated by the
// definition.
for (; BB != DefBB; BB = getImmediateDominator(BB, DT)) {
if (BB != UseBB && !M.LiveThrough.insert(BB))
break;
}
}