[llvm] [X86][PartialReduction] Lower zext-byte add reductions to vpsadbw (PR #201076)

[Simon Pilgrim via llvm-commits]

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+; RUN: opt < %s -passes='expand-reductions,x86-partial-reduction' -mtriple=x86_64-unknown-unknown -mattr=+avx2 -S | FileCheck %s
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RKSimon wrote:

move these to phaseordering/x86?

https://github.com/llvm/llvm-project/pull/201076