[all-commits] [llvm/llvm-project] 2d756d: [NFC][Codegen][X86] Add tests where we could impro...

[Roman Lebedev via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 2d756d25e68826787277ecf532048dd6d55eb2d0
      https://github.com/llvm/llvm-project/commit/2d756d25e68826787277ecf532048dd6d55eb2d0
  Author: Roman Lebedev <lebedev.ri at gmail.com>
  Date:   2022-12-23 (Fri, 23 Dec 2022)

  Changed paths:
    M llvm/test/CodeGen/X86/freeze-vector.ll

  Log Message:
  -----------
  [NFC][Codegen][X86] Add tests where we could improve `freeze` handling


  Commit: f5700e7b69048de958172fb513b336564e7f8709
      https://github.com/llvm/llvm-project/commit/f5700e7b69048de958172fb513b336564e7f8709
  Author: Roman Lebedev <lebedev.ri at gmail.com>
  Date:   2022-12-23 (Fri, 23 Dec 2022)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    M llvm/test/CodeGen/X86/freeze-vector.ll

  Log Message:
  -----------
  [DAGCombine][X86] Pull one-use `freeze` out of `extract_vector_elt` vector operand

This may allow us to further simplify the vector,
and freezing the extracted result is still fine:
```
----------------------------------------
define i8 @src(<2 x i8> %src, i64 %idx) {
%0:
  %i1 = freeze <2 x i8> %src
  %i2 = extractelement <2 x i8> %i1, i64 %idx
  ret i8 %i2
}
=>
define i8 @tgt(<2 x i8> %src, i64 %idx) {
%0:
  %i1 = extractelement <2 x i8> %src, i64 %idx
  %i2 = freeze i8 %i1
  ret i8 %i2
}
Transformation seems to be correct!
```

BUT, there must not be other uses of that freeze,
see `@freeze_extractelement_extra_use`.

Also, looks like we are missing some ISEL-level handling for freeze.


Compare: https://github.com/llvm/llvm-project/compare/46cd3127fe54...f5700e7b6904