[LoopUnrolling] Fix loop size check for peeling
Summary:
We should check if loop size allows us to peel at least one iteration
before we do so.
Patch by Max Kazantsev!
Reviewers: sanjoy, mkuper, efriedma
Reviewed By: mkuper
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D30632
llvm-svn: 297122
diff --git a/llvm/lib/Transforms/Utils/LoopUnrollPeel.cpp b/llvm/lib/Transforms/Utils/LoopUnrollPeel.cpp
index 55bfc25..b8147fc 100644
--- a/llvm/lib/Transforms/Utils/LoopUnrollPeel.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnrollPeel.cpp
@@ -75,7 +75,9 @@
// its only back edge. If there is such Phi, peeling 1 iteration from the
// loop is profitable, because starting from 2nd iteration we will have an
// invariant instead of this Phi.
- if (auto *BackEdge = L->getLoopLatch()) {
+ if (LoopSize <= UP.Threshold) {
+ BasicBlock *BackEdge = L->getLoopLatch();
+ assert(BackEdge && "Loop is not in simplified form?");
BasicBlock *Header = L->getHeader();
// Iterate over Phis to find one with invariant input on back edge.
bool FoundCandidate = false;