[llvm] [GVN] Track visited nodes in equality propagation to avoid OOM (PR #212265)

[Antonio Frighetto via llvm-commits]

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@@ -3092,6 +3092,7 @@ bool GVNPass::propagateEquality(
     Value *LHS, Value *RHS,
     const std::variant<BasicBlockEdge, Instruction *> &Root) {
   SmallVector<std::pair<Value*, Value*>, 4> Worklist;
+  llvm::DenseSet<std::pair<Value *, Value *>> Visited;
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antoniofrighetto wrote:

```suggestion
  DenseSet<std::pair<Value *, Value *>> Visited;
```

https://github.com/llvm/llvm-project/pull/212265