[InstCombine] Use MapVector for SourceAggregates. #132564
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foldAggregateConstructionIntoAggregateReuse iterates over the entries of SourceAggregates and the order of inserted instructions depends on the order of the iterator. Using a regular DenseMap can lead to non-deterministic value naming/numbering. I don't think it can actually impact the generated binary, but it makes diffing IR more difficult. If desired, I could provide a test case showing the difference in naming.
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@llvm/pr-subscribers-llvm-transforms Author: Florian Hahn (fhahn) ChangesfoldAggregateConstructionIntoAggregateReuse iterates over the entries of SourceAggregates and the order of inserted instructions depends on the order of the iterator. Using a regular DenseMap can lead to non-deterministic value naming/numbering. I don't think it can actually impact the generated binary, but it makes diffing IR more difficult. If desired, I could provide a test case showing the difference in naming. Full diff: https://github.com/llvm/llvm-project/pull/132564.diff 1 Files Affected:
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp b/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
index 6860a7cd07b78..f897cc7855d2d 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
@@ -1111,7 +1111,7 @@ Instruction *InstCombinerImpl::foldAggregateConstructionIntoAggregateReuse(
// For each predecessor, what is the source aggregate,
// from which all the elements were originally extracted from?
// Note that we want for the map to have stable iteration order!
- SmallDenseMap<BasicBlock *, Value *, 4> SourceAggregates;
+ SmallMapVector<BasicBlock *, Value *, 4> SourceAggregates;
bool FoundSrcAgg = false;
for (BasicBlock *Pred : Preds) {
std::pair<decltype(SourceAggregates)::iterator, bool> IV =
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foldAggregateConstructionIntoAggregateReuse iterates over the entries of SourceAggregates and the order of inserted instructions depends on the order of the iterator. Using a regular DenseMap can lead to non-deterministic value naming/numbering. I don't think it can actually impact the generated binary, but it makes diffing IR more difficult. PR: llvm/llvm-project#132564
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foldAggregateConstructionIntoAggregateReuse iterates over the entries of SourceAggregates and the order of inserted instructions depends on the order of the iterator. Using a regular DenseMap can lead to non-deterministic value naming/numbering.
I don't think it can actually impact the generated binary, but it makes diffing IR more difficult. If desired, I could provide a test case showing the difference in naming.