[llvm] [AArch64,TTI] Remove RealUse check for vector insert/extract costs. (PR #146526)

[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/test/Transforms/SLPVectorizer/AArch64/extract-subvector-long-input.ll llvm/test/Transforms/SLPVectorizer/AArch64/phi-node-bitwidt-op-not.ll llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp llvm/lib/Target/AArch64/AArch64TargetTransformInfo.h llvm/test/Analysis/CostModel/AArch64/reduce-add.ll llvm/test/Analysis/CostModel/AArch64/reduce-and.ll llvm/test/Analysis/CostModel/AArch64/reduce-or.ll llvm/test/Analysis/CostModel/AArch64/reduce-xor.ll llvm/test/Analysis/CostModel/AArch64/shuffle-other.ll llvm/test/Analysis/CostModel/AArch64/shuffle-select.ll llvm/test/Analysis/CostModel/AArch64/sve-intrinsics.ll llvm/test/Transforms/LowerMatrixIntrinsics/dot-product-transpose-int.ll llvm/test/Transforms/SLPVectorizer/AArch64/ext-trunc.ll llvm/test/Transforms/SLPVectorizer/AArch64/external-use-icmp.ll llvm/test/Transforms/SLPVectorizer/AArch64/extractelements-to-shuffle.ll llvm/test/Transforms/SLPVectorizer/AArch64/gather-buildvector-with-minbitwidth-user.ll llvm/test/Transforms/SLPVectorizer/AArch64/getelementptr.ll llvm/test/Transforms/SLPVectorizer/AArch64/getelementptr2.ll llvm/test/Transforms/SLPVectorizer/AArch64/memory-runtime-checks.ll llvm/test/Transforms/SLPVectorizer/AArch64/multiple_reduction.ll llvm/test/Transforms/SLPVectorizer/AArch64/splat-loads.ll llvm/test/Transforms/SLPVectorizer/AArch64/unreachable-blocks-with-phis.ll llvm/test/Transforms/SLPVectorizer/AArch64/vector-getelementptr.ll llvm/test/Transforms/SLPVectorizer/AArch64/vectorizable-selects-uniform-cmps.ll llvm/test/Transforms/SLPVectorizer/alternate-opcode-sindle-bv.ll llvm/test/Transforms/VectorCombine/AArch64/load-extractelement-scalarization.ll llvm/test/Transforms/SLPVectorizer/X86/extract-subvector-long-input.ll llvm/test/Transforms/SLPVectorizer/X86/icmp-altopcode-after-reordering.ll llvm/test/Transforms/SLPVectorizer/X86/phi-node-bitwidt-op-not.ll
``````````

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The following files introduce new uses of undef:
 - llvm/test/Transforms/SLPVectorizer/AArch64/extract-subvector-long-input.ll
 - llvm/test/Transforms/SLPVectorizer/X86/extract-subvector-long-input.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/146526