[llvm] [VectorCombine] Fix scalarizeExtExtract for big-endian (PR #157962)

[Simon Pilgrim via llvm-commits]

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+; RUN: opt -passes='vector-combine,dce' -S -mtriple=aarch64-unknown-linux-gnu %s -o - | FileCheck %s --check-prefix=LE
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RKSimon wrote:

yes, this fold is cost driven - it will need to be put under the AArch64 subdir and tested on aarch64 / aarch64_be triples

https://github.com/llvm/llvm-project/pull/157962