[PATCH] D157267: [NewGVN] Fix an use after free when updating use count

[Konstantina Mitropoulou via Phabricator via llvm-commits]

kmitropoulou added inline comments.


================
Comment at: llvm/lib/Transforms/Scalar/NewGVN.cpp:4119
           if (isSSACopy) {
             unsigned &IIUseCount = UseCounts[II];
             if (--IIUseCount == 0)
----------------
The test case does not crash in my workspace. Anyway, I think the problem is here. If II is not in the UseCounts map, then it just adds it and it returns zero. Will the following change solve the problem?

if (isSSACopy) {
    auto It = UseCounts.find(II);
    if (It != UseCounts.end()) {
        unsigned &IIUseCount = It->second;
        if (--IIUseCount == 0)
             ProbablyDead.insert(II);
    }
}



CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D157267/new/

https://reviews.llvm.org/D157267