[PATCH] D61129: [InstSimplify][X86] Expand PACKSS/PACKUS if the operands won't saturate

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon created this revision.
RKSimon added reviewers: craig.topper, spatel, andreadb.
Herald added a project: LLVM.

If we know the source operands are already in range for PACKS/PACKUS then expand these to generic shuffle+truncate IR to allow us to further combine them.

DAG can lower these back to PACKSS/PACKUS without much trouble if they don't fold.

This was noticed while investigating PR39984.


Repository:
  rL LLVM

https://reviews.llvm.org/D61129

Files:
  lib/Transforms/InstCombine/InstCombineCalls.cpp
  test/Transforms/InstCombine/X86/x86-pack.ll

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