[llvm] [X86] Fix arithmetic error in extractVector (PR #128052)

[Phoebe Wang via llvm-commits]

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@@ -0,0 +1,30 @@
+; Ensure assertion is not hit when folding concat of two contiguous extract_subvector operations
+; from a source with a non-power-of-two vector length.
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phoebewang wrote:

It doesn't crash on trunk? https://godbolt.org/z/vrvcGE71z

https://github.com/llvm/llvm-project/pull/128052