[all-commits] [llvm/llvm-project] 13c359: [X86] ReplaceNodeResults - truncate sub-128-bit ve...

[Simon Pilgrim via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 13c359aa9b5eae0715494505d989cfc8ed1d39cf
      https://github.com/llvm/llvm-project/commit/13c359aa9b5eae0715494505d989cfc8ed1d39cf
  Author: Simon Pilgrim <RKSimon at users.noreply.github.com>
  Date:   2024-02-27 (Tue, 27 Feb 2024)

  Changed paths:
    M llvm/lib/Target/X86/X86ISelLowering.cpp
    M llvm/test/CodeGen/X86/extract-concat.ll
    M llvm/test/CodeGen/X86/vec_anyext.ll
    M llvm/test/CodeGen/X86/vec_cast.ll

  Log Message:
  -----------
  [X86] ReplaceNodeResults - truncate sub-128-bit vectors as shuffles directly (#83120)

We were scalarizing these truncations, but in most cases we can widen the source vector to 128-bits and perform the truncation as a shuffle directly (which will usually lower as a PACK or PSHUFB).

For the cases where the widening and shuffle isn't legal we can leave it to generic legalization to scalarize for us.

Fixes #81883



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