[llvm] Passes for widening vector operations and shuffle opt (PR #169559)

[via llvm-commits]

github-actions[bot] wrote:

<!--LLVM CODE FORMAT COMMENT: {undef deprecator}-->


:warning: undef deprecator found issues in your code. :warning:

<details>
<summary>
You can test this locally with the following command:
</summary>

``````````bash
git diff -U0 --pickaxe-regex -S '([^a-zA-Z0-9#_-]undef([^a-zA-Z0-9_-]|$)|UndefValue::get)' 'HEAD~1' HEAD llvm/lib/Target/Hexagon/HexagonGenWideningVecFloatInstr.cpp llvm/lib/Target/Hexagon/HexagonGenWideningVecInstr.cpp llvm/lib/Target/Hexagon/HexagonOptShuffleVector.cpp llvm/test/CodeGen/Hexagon/bug54537-vavg.ll llvm/test/CodeGen/Hexagon/extend-multiply-for-output-fpext.ll llvm/test/CodeGen/Hexagon/no_widening_of_bf16_vecmul.ll llvm/test/CodeGen/Hexagon/shortvec-vasrsat.ll llvm/test/CodeGen/Hexagon/shortvec-vavg.ll llvm/test/CodeGen/Hexagon/shortvec-vmpy.ll llvm/test/CodeGen/Hexagon/vadd-const.ll llvm/test/CodeGen/Hexagon/vasr-sat.ll llvm/test/CodeGen/Hexagon/vavg.ll llvm/test/CodeGen/Hexagon/vec-shuff-invalid-operand.ll llvm/test/CodeGen/Hexagon/vec-shuff-multi-uses.ll llvm/test/CodeGen/Hexagon/vec-shuff2.ll llvm/test/CodeGen/Hexagon/vmpa.ll llvm/test/CodeGen/Hexagon/vmpy-const.ll llvm/test/CodeGen/Hexagon/vmpy-qfp-const.ll llvm/test/CodeGen/Hexagon/vsub-const.ll llvm/test/CodeGen/Hexagon/widening-float-vec.ll llvm/test/CodeGen/Hexagon/widening-vec.ll llvm/test/CodeGen/Hexagon/widening-vec2.ll llvm/lib/Target/Hexagon/Hexagon.h llvm/lib/Target/Hexagon/HexagonGenPredicate.cpp llvm/lib/Target/Hexagon/HexagonISelLowering.h llvm/lib/Target/Hexagon/HexagonISelLoweringHVX.cpp llvm/lib/Target/Hexagon/HexagonNewValueJump.cpp llvm/lib/Target/Hexagon/HexagonTargetMachine.cpp llvm/lib/Target/Hexagon/HexagonVectorCombine.cpp llvm/lib/Target/Hexagon/MCTargetDesc/HexagonMCELFStreamer.cpp llvm/test/CodeGen/Hexagon/autohvx/isel-vpackew.ll llvm/test/CodeGen/Hexagon/autohvx/widen-setcc.ll
``````````

</details>


The following files introduce new uses of undef:
 - llvm/lib/Target/Hexagon/HexagonGenWideningVecFloatInstr.cpp
 - llvm/lib/Target/Hexagon/HexagonGenWideningVecInstr.cpp
 - llvm/lib/Target/Hexagon/HexagonOptShuffleVector.cpp
 - llvm/test/CodeGen/Hexagon/bug54537-vavg.ll
 - llvm/test/CodeGen/Hexagon/shortvec-vasrsat.ll
 - llvm/test/CodeGen/Hexagon/shortvec-vavg.ll
 - llvm/test/CodeGen/Hexagon/shortvec-vmpy.ll
 - llvm/test/CodeGen/Hexagon/vasr-sat.ll
 - llvm/test/CodeGen/Hexagon/vavg.ll
 - llvm/test/CodeGen/Hexagon/vec-shuff-invalid-operand.ll
 - llvm/test/CodeGen/Hexagon/vec-shuff-multi-uses.ll
 - llvm/test/CodeGen/Hexagon/vmpa.ll
 - llvm/test/CodeGen/Hexagon/widening-vec2.ll

[Undef](https://llvm.org/docs/LangRef.html#undefined-values) is now deprecated and should only be used in the rare cases where no replacement is possible. For example, a load of uninitialized memory yields `undef`. You should use `poison` values for placeholders instead.

In tests, avoid using `undef` and having tests that trigger undefined behavior. If you need an operand with some unimportant value, you can add a new argument to the function and use that instead.

For example, this is considered a bad practice:
```llvm
define void @fn() {
  ...
  br i1 undef, ...
}
```

Please use the following instead:
```llvm
define void @fn(i1 %cond) {
  ...
  br i1 %cond, ...
}
```

Please refer to the [Undefined Behavior Manual](https://llvm.org/docs/UndefinedBehavior.html) for more information.



https://github.com/llvm/llvm-project/pull/169559