[CodeGenPrepare] avoid crashing from replacing a phi twice
Summary:
This is a fix to bug 41052:
https://bugs.llvm.org/show_bug.cgi?id=41052
While trying to optimize a memory instruction in a dead basic block, we end up registering the same phi for replacement twice. This patch avoids registering more than the first replacement candidate for a phi.
Patch by: JesperAntonsson
Reviewers: skatkov, aprantl
Reviewed By: aprantl
Subscribers: jdoerfert, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D59358
llvm-svn: 356260
diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp
index e8498eb..44f1709 100644
--- a/llvm/lib/CodeGen/CodeGenPrepare.cpp
+++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp
@@ -3282,6 +3282,8 @@
PhiNodeSet &PhiNodesToMatch) {
SmallVector<PHIPair, 8> WorkList;
Matcher.insert({ PHI, Candidate });
+ SmallSet<PHINode *, 8> MatchedPHIs;
+ MatchedPHIs.insert(PHI);
WorkList.push_back({ PHI, Candidate });
SmallSet<PHIPair, 8> Visited;
while (!WorkList.empty()) {
@@ -3314,8 +3316,10 @@
if (Matcher.count({ FirstPhi, SecondPhi }))
continue;
// So the values are different and does not match. So we need them to
- // match.
- Matcher.insert({ FirstPhi, SecondPhi });
+ // match. (But we register no more than one match per PHI node, so that
+ // we won't later try to replace them twice.)
+ if (!MatchedPHIs.insert(FirstPhi).second)
+ Matcher.insert({ FirstPhi, SecondPhi });
// But me must check it.
WorkList.push_back({ FirstPhi, SecondPhi });
}