Enhance LiveValues to work on PHI operands.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@67523 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/LiveValues.cpp b/lib/Analysis/LiveValues.cpp
index 21ddf6b..7fc97c9 100644
--- a/lib/Analysis/LiveValues.cpp
+++ b/lib/Analysis/LiveValues.cpp
@@ -142,21 +142,32 @@
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;
}
}