[llvm] [AMDGPU][True16][CodeGen] uaddsat/usubsat true16 selection in gisel (PR #128233)

[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)' b11e1baf22a4a5d061a112c490f54f5e767f79e4 8f73cc42f62d73bf360f13b5d016302ddf9d1780 llvm/lib/Target/AMDGPU/AMDGPUInstructionSelector.cpp llvm/lib/Target/AMDGPU/AMDGPULegalizerInfo.cpp llvm/lib/Target/AMDGPU/SIRegisterInfo.cpp llvm/lib/Target/AMDGPU/SIRegisterInfo.h llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.cpp llvm/test/CodeGen/AMDGPU/GlobalISel/uaddsat.ll llvm/test/CodeGen/AMDGPU/GlobalISel/usubsat.ll llvm/test/CodeGen/AMDGPU/fadd.f16.ll llvm/test/CodeGen/AMDGPU/fma.f16.ll llvm/test/CodeGen/AMDGPU/fmed3.ll llvm/test/CodeGen/AMDGPU/llvm.ldexp.ll llvm/test/CodeGen/AMDGPU/shrink-add-sub-constant.ll llvm/test/CodeGen/AMDGPU/v_pack.ll
``````````

</details>


The following files introduce new uses of undef:
 - llvm/lib/Target/AMDGPU/AMDGPUInstructionSelector.cpp

[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/128233