[PATCH] D23723: [SLP] Avoid signed integer overflow

[Matthew Simpson via llvm-commits]

mssimpso updated the summary for this revision.
mssimpso added a subscriber: gberry.
mssimpso updated this revision to Diff 68913.
mssimpso added a comment.
Herald added a reviewer: vkalintiris.

Hi Michael,

According to @gberry, the signed SaturatingAdd implementation I added isn't well-defined as you guessed. I started rewriting it, but I think a better solution might be to avoid INT_MAX all together. We're using INT_MAX to essentially indicate "do not vectorize". I think it makes better sense to put the INT_MAX logic in a function that returns a bool.

I've updated the patch to do this. I've also kept the existing test case intact, and added a new run-line checking for no vectorization. The test was being vectorized by chance due to the undefined behavior.


https://reviews.llvm.org/D23723

Files:
  lib/Transforms/Vectorize/SLPVectorizer.cpp
  test/Transforms/SLPVectorizer/AArch64/gather-root.ll

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