[clang] [llvm] [AARCH64][Neon] switch to using bitcasts in arm_neon.h where appropriate (PR #127043)

[via cfe-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)' 242aa8c743fe4344844753d8faf59744235319df 264ffc863e48426a221b55b486ebfb36dd19efdc llvm/test/CodeGen/AArch64/v8.2a-neon-intrinsics-constrained.ll clang/include/clang/Basic/TargetBuiltins.h clang/lib/CodeGen/CGBuiltin.cpp clang/lib/CodeGen/CodeGenFunction.h clang/test/CodeGen/AArch64/bf16-dotprod-intrinsics.c clang/test/CodeGen/AArch64/bf16-getset-intrinsics.c clang/test/CodeGen/AArch64/bf16-reinterpret-intrinsics.c clang/test/CodeGen/AArch64/fp8-intrinsics/acle_neon_fp8_cvt.c clang/test/CodeGen/AArch64/fp8-intrinsics/acle_neon_fp8_fdot.c clang/test/CodeGen/AArch64/fp8-intrinsics/acle_neon_fp8_fmla.c clang/test/CodeGen/AArch64/fp8-intrinsics/acle_neon_fp8_reinterpret.c clang/test/CodeGen/AArch64/neon-2velem.c clang/test/CodeGen/AArch64/neon-extract.c clang/test/CodeGen/AArch64/neon-fma.c clang/test/CodeGen/AArch64/neon-fp16fml.c clang/test/CodeGen/AArch64/neon-intrinsics-constrained.c clang/test/CodeGen/AArch64/neon-intrinsics.c clang/test/CodeGen/AArch64/neon-ldst-one-rcpc3.c clang/test/CodeGen/AArch64/neon-ldst-one.c clang/test/CodeGen/AArch64/neon-misc-constrained.c clang/test/CodeGen/AArch64/neon-misc.c clang/test/CodeGen/AArch64/neon-perm.c clang/test/CodeGen/AArch64/neon-scalar-x-indexed-elem-constrained.c clang/test/CodeGen/AArch64/neon-scalar-x-indexed-elem.c clang/test/CodeGen/AArch64/neon-vcmla.c clang/test/CodeGen/AArch64/poly-add.c clang/test/CodeGen/AArch64/poly128.c clang/test/CodeGen/AArch64/poly64.c clang/test/CodeGen/AArch64/v8.1a-neon-intrinsics.c clang/test/CodeGen/AArch64/v8.2a-neon-intrinsics-constrained.c clang/test/CodeGen/AArch64/v8.2a-neon-intrinsics-generic.c clang/test/CodeGen/AArch64/v8.2a-neon-intrinsics.c clang/test/CodeGen/AArch64/v8.5a-neon-frint3264-intrinsic.c clang/test/CodeGen/AArch64/v8.6a-neon-intrinsics.c clang/test/CodeGen/arm-bf16-dotprod-intrinsics.c clang/test/CodeGen/arm-bf16-getset-intrinsics.c clang/test/CodeGen/arm-neon-directed-rounding.c clang/test/CodeGen/arm-neon-fma.c clang/test/CodeGen/arm-neon-numeric-maxmin.c clang/test/CodeGen/arm-neon-vcvtX.c clang/test/CodeGen/arm-neon-vst.c clang/test/CodeGen/arm64-vrnd-constrained.c clang/test/CodeGen/arm64-vrnd.c clang/test/CodeGen/arm64_vcreate.c clang/test/CodeGen/arm64_vdupq_n_f64.c clang/test/CodeGen/arm_neon_intrinsics.c clang/utils/TableGen/NeonEmitter.cpp
``````````

</details>


The following files introduce new uses of undef:
 - clang/test/CodeGen/AArch64/bf16-reinterpret-intrinsics.c
 - clang/test/CodeGen/AArch64/fp8-intrinsics/acle_neon_fp8_reinterpret.c
 - clang/test/CodeGen/AArch64/neon-2velem.c
 - clang/test/CodeGen/AArch64/neon-extract.c
 - clang/test/CodeGen/AArch64/neon-intrinsics-constrained.c
 - clang/test/CodeGen/AArch64/neon-intrinsics.c
 - clang/test/CodeGen/AArch64/neon-ldst-one-rcpc3.c
 - clang/test/CodeGen/AArch64/neon-ldst-one.c
 - clang/test/CodeGen/AArch64/neon-misc.c
 - clang/test/CodeGen/AArch64/neon-scalar-x-indexed-elem-constrained.c
 - clang/test/CodeGen/AArch64/neon-scalar-x-indexed-elem.c
 - clang/test/CodeGen/AArch64/neon-vcmla.c
 - clang/test/CodeGen/AArch64/v8.5a-neon-frint3264-intrinsic.c
 - clang/test/CodeGen/arm-neon-vst.c
 - clang/test/CodeGen/arm64_vdupq_n_f64.c
 - clang/test/CodeGen/arm_neon_intrinsics.c

[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/127043