================
@@ -5194,6 +5252,36 @@ selectPartitionType(Partition &P, const DataLayout &DL,
AllocaInst &AI,
isIntegerWideningViable(P, LargestIntTy, DL))
return {LargestIntTy, true, nullptr};
+ // Try homogeneous struct to vector canonicalization, but only when
+ // the conversion would actually benefit from vectorization: either
+ // the partition has non-splittable typed uses, or the alloca is
+ // involved in phi/select patterns (enabling speculation).
+ //
+ // When all uses are splittable (memcpy/lifetime only) and there's no
+ // phi/select involvement, converting to vector just changes memcpy
+ // split types without enabling promotion, propagating vector types to
+ // other allocas and causing insertelement/extractelement overhead.
+ {
+ bool HasNonSplittable =
+ any_of(P, [](const Slice &S) { return !S.isSplittable(); });
+ bool ShouldConvert = HasNonSplittable;
+ if (!ShouldConvert) {
+ ShouldConvert = any_of(AI.users(), [&AI](const User *U) {
----------------
vtjnash wrote:
My understanding of this part of the pass is that you're only permitted to look
at the slices in Partition P here, and not allowed to look directly at
`AI.users()`
https://github.com/llvm/llvm-project/pull/165159
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