Cheers! Can you commit on my behalf?

Sorry for the delay. I've separated commits that adds tests to https://reviews.llvm.org/D120214, and make this commit only show the difference between older version.

Thanks! Can you commit on my behalf?

Remove space.

Use simpler pattern based on https://reviews.llvm.org/D112204

https://alive2.llvm.org/ce/z/2KoTdr It always passes unless I put nsw on sub in tgt block. I guess that means it's okay.

IIUC, if nsw flag is not specified it will wrap around, then -(-128) = -128, still yielding the same result. Even if nsw flag is specified, I can define poison value as anything I want so it's still fine?

I like your method! It's always reducing negation or keeping the same number of negation unless x and y are both non-negative and it can account for nabs case very well. I was trying to tidy your patch a bit and add some more test cases to address the comments by david-arm and submit it here. However, one thing came to concern me.

typo

Tidy up test case and code.

Account for comments

Edit existing test

Edit typos

Remove unused line

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@fhahn @dmgreen I've accounted for your comments. Please take a look again!

@fhahn I've shrinked the test case. Could you take a look?

Make test case compact.

Tidy up testcases.