[PATCH] D68643: [Codegen] Alter the default promotion for add_sat and sub_sat

[Nikita Popov via Phabricator via llvm-commits]

nikic accepted this revision.
nikic added a comment.
This revision is now accepted and ready to land.

LGTM

> This still uses the existing promotion when the promoted add/sub_sat is legal. In many situations (but not all) it would probably be better to just perform the new promotion.

I guess at least for the unsigned case, it would be reasonable to use the shift+sat expansion only if both the sat is legal *and* min/max is not legal. The umax+sub expansion at least is clearly better than usubsat + 3 shifts.

But that's probably better left for a followup patch.


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https://reviews.llvm.org/D68643