Don't track users of undef values; they aren't interesting for
register pressure.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@105501 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index 86ea3eb..94df955 100644
--- a/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -2095,8 +2095,12 @@
} else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
if (!Inserted.insert(U)) continue;
const Value *V = U->getValue();
- if (const Instruction *Inst = dyn_cast<Instruction>(V))
+ if (const Instruction *Inst = dyn_cast<Instruction>(V)) {
+ // Look for instructions defined outside the loop.
if (L->contains(Inst)) continue;
+ } else if (isa<UndefValue>(V))
+ // Undef doesn't have a live range, so it doesn't matter.
+ continue;
for (Value::const_use_iterator UI = V->use_begin(), UE = V->use_end();
UI != UE; ++UI) {
const Instruction *UserInst = dyn_cast<Instruction>(*UI);