[PATCH] D71064: [InstCombine] Invert `add A, sext(B) --> sub A, zext(B)` canonicalization (to `sub A, zext B -> add A, sext B`)

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

In D71064#1770937 <https://reviews.llvm.org/D71064#1770937>, @spatel wrote:

> Did you confirm that codegen is equal or better for these cases?
>  I think we have DAGCombiner reversals for this transform, but some targets that seem like they would benefit have not enabled the TLI hook.


I didn't yet. So, as far as i can tell, these are all the interesting cases:
(i'm looking at `@t0_new_canon` vs `@t1_old_canon` since that is the only change in this patch)
https://godbolt.org/z/vbb25Q - no regression for x86
https://godbolt.org/z/Htg7m5 - aarch64 also looks ok?
https://godbolt.org/z/xmP6JV - arm good?
https://godbolt.org/z/vNrNJ8 - thumb good?

So i'd say everything is already covered by backend undo folds?
Let me know if i'm missing the point here?

> (apart from the fuzzer tests - I agree that those are not important)

Good to know.


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https://reviews.llvm.org/D71064