[JumpThread] Simplify CmpInst-as-Condition branch-folding a bit.
Summary: Simplify CmpInst-as-Condition branch-folding a bit.
Reviewers: sanjoy, efriedma
Reviewed By: efriedma
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D30429
llvm-svn: 297186
diff --git a/llvm/lib/Transforms/Scalar/JumpThreading.cpp b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
index fb784ff..566ebed 100644
--- a/llvm/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
@@ -808,7 +808,12 @@
// TODO: This should be extended to handle switches as well.
BranchInst *CondBr = dyn_cast<BranchInst>(BB->getTerminator());
Constant *CondConst = dyn_cast<Constant>(CondCmp->getOperand(1));
- if (CondBr && CondConst && CondBr->isConditional()) {
+ if (CondBr && CondConst) {
+ // We should have returned as soon as we turn a conditional branch to
+ // unconditional. Because its no longer interesting as far as jump
+ // threading is concerned.
+ assert(CondBr->isConditional() && "Threading on unconditional terminator");
+
LazyValueInfo::Tristate Ret =
LVI->getPredicateAt(CondCmp->getPredicate(), CondCmp->getOperand(0),
CondConst, CondBr);
@@ -831,10 +836,12 @@
}
return true;
}
- }
- if (CondBr && CondConst && TryToUnfoldSelect(CondCmp, BB))
- return true;
+ // We did not manage to simplify this branch, try to see whether
+ // CondCmp depends on a known phi-select pattern.
+ if (TryToUnfoldSelect(CondCmp, BB))
+ return true;
+ }
}
// Check for some cases that are worth simplifying. Right now we want to look