[PATCH] D70844: [InstCombine] Fix big-endian miscompile of (bitcast (zext/trunc (bitcast)))

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri accepted this revision.
lebedev.ri added a comment.
This revision is now accepted and ready to land.

LGTM now, thank you.
Up to you if you want to wait for yet another review (@spatel ?)



================
Comment at: llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp:1871
+  // Produce an identify shuffle mask for the src vector.
+  ShuffleMaskStorage.resize(SrcElts);
+  std::iota(ShuffleMaskStorage.begin(), ShuffleMaskStorage.end(), 0);
----------------
maybe let's do
```
 ShuffleMaskStorage.reserve(std::max(SrcElts, DestElts));
 ShuffleMaskStorage.resize(SrcElts);
```
to try to avoid allocs in widening case.
Though we then waste memory in truncating case.


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https://reviews.llvm.org/D70844