[all-commits] [llvm/llvm-project] e4d25a: [DAG] BUILD_VECTOR: absorb ZERO_EXTEND of a single...

[Roman Lebedev via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: e4d25a9c234b1501bc4ac01f4e40d75f6ebee172
      https://github.com/llvm/llvm-project/commit/e4d25a9c234b1501bc4ac01f4e40d75f6ebee172
  Author: Roman Lebedev <lebedev.ri at gmail.com>
  Date:   2022-12-31 (Sat, 31 Dec 2022)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    M llvm/test/CodeGen/AArch64/build-vector-extract.ll
    M llvm/test/CodeGen/X86/buildvec-extract.ll

  Log Message:
  -----------
  [DAG] BUILD_VECTOR: absorb ZERO_EXTEND of a single first operand if all other ops are zeros

This kind of pattern seems to come up as regressions
with better ZERO_EXTEND_VECTOR_INREG recognition.

For initial implementation, this is quite restricted
to the minimal viable transform, otherwise there are
too many regressions to be dealt with.