[PATCH] D38378: Optimize {s|u}add.with.overflow on ARM.

[Kristof Beyls via Phabricator via llvm-commits]

kristof.beyls added a comment.

Hi Joel,

Is my impression correct that this should improve code size and potentially performance in general, not just for the overflow intrinsics?
If so, did you manage to collect any numbers of the impact of this patch on code size and/or performance on some benchmark?

One other high-level thought is that it isn't just sub and add instructions that can set flags and potentially remove the need for a compare instruction.
I'm afraid I don't have a feel for how often a compare can be eliminate by using subs/adds or other flag-setting instructions.
I wonder if the changes in this patch could be generalized to enable flag-setting instructions other than adds/subs to remove compare instructions too?
Not that I think that necessarily needs to be done in this patch - just wondering if this patch is an incremental step towards enabling even more removal of compare instructions.

Thanks!

Kristof


https://reviews.llvm.org/D38378