[llvm] [SLP]Exclude non-profitable subtrees. (PR #162018)

[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/Transforms/Vectorize/SLPVectorizer.cpp llvm/test/Transforms/PhaseOrdering/X86/vector-reductions.ll llvm/test/Transforms/SLPVectorizer/AArch64/div.ll llvm/test/Transforms/SLPVectorizer/AArch64/gather-buildvector-with-minbitwidth-user.ll llvm/test/Transforms/SLPVectorizer/AArch64/reused-scalar-repeated-in-node.ll llvm/test/Transforms/SLPVectorizer/RISCV/complex-loads.ll llvm/test/Transforms/SLPVectorizer/RISCV/partial-vec-invalid-cost.ll llvm/test/Transforms/SLPVectorizer/RISCV/reordered-buildvector-scalars.ll llvm/test/Transforms/SLPVectorizer/X86/PR40310.ll llvm/test/Transforms/SLPVectorizer/X86/alternate-int-inseltpoison.ll llvm/test/Transforms/SLPVectorizer/X86/alternate-int.ll llvm/test/Transforms/SLPVectorizer/X86/arith-fp-inseltpoison.ll llvm/test/Transforms/SLPVectorizer/X86/arith-fp.ll llvm/test/Transforms/SLPVectorizer/X86/buildvector-shuffle.ll llvm/test/Transforms/SLPVectorizer/X86/buildvectors-parent-phi-nodes.ll llvm/test/Transforms/SLPVectorizer/X86/c-ray.ll llvm/test/Transforms/SLPVectorizer/X86/delayed-gather-emission.ll llvm/test/Transforms/SLPVectorizer/X86/entry-no-bundle-but-extra-use-on-vec.ll llvm/test/Transforms/SLPVectorizer/X86/gather-with-cmp-user.ll llvm/test/Transforms/SLPVectorizer/X86/original-inst-scheduled-after-copyable.ll llvm/test/Transforms/SLPVectorizer/X86/phi-node-with-cycle.ll llvm/test/Transforms/SLPVectorizer/X86/pr46983.ll llvm/test/Transforms/SLPVectorizer/X86/reduction2.ll llvm/test/Transforms/SLPVectorizer/X86/reschedule-only-scheduled.ll llvm/test/Transforms/SLPVectorizer/X86/same-last-instruction-different-parents.ll llvm/test/Transforms/SLPVectorizer/X86/scalarize-ctlz.ll llvm/test/Transforms/SLPVectorizer/X86/split-node-reorder-node-with-ops.ll llvm/test/Transforms/SLPVectorizer/X86/subvector-minbitwidth-unsigned-value.ll llvm/test/Transforms/SLPVectorizer/X86/trunced-buildvector-scalar-extended.ll llvm/test/Transforms/SLPVectorizer/X86/vec3-reorder-reshuffle.ll llvm/test/Transforms/SLPVectorizer/gather_extract_from_vectorbuild.ll llvm/test/Transforms/SLPVectorizer/vectorize-reorder-alt-shuffle.ll
``````````

</details>


The following files introduce new uses of undef:
 - llvm/test/Transforms/SLPVectorizer/X86/arith-fp.ll
 - llvm/test/Transforms/SLPVectorizer/X86/reschedule-only-scheduled.ll
 - llvm/test/Transforms/SLPVectorizer/vectorize-reorder-alt-shuffle.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/162018