[PATCH] D149407: [ValueTracking] Pull out logic for detecting if `(add X, Y)` is non-zero; NFC

[Nikita Popov via Phabricator via llvm-commits]

nikic added inline comments.


================
Comment at: llvm/lib/Analysis/ValueTracking.cpp:2840
       return true;
     break;
   }
----------------
goldstein.w.n wrote:
> nikic wrote:
> > Can we directly return isNonZeroAdd?
> No, we actually benefit from compute known bits. Take the following. `X[0] == 0` and `Y[0] == 1`. The result will be odd (from computeknownbits) so non-zero, but we don't get that here (would need to replicate computeknownnbits to do that).
Okay, can we then just call `KnownBits::computeForAddSub(...).isNonZero()` at the end? After all we already calculated known bits for both operands, so no point in calculating them again via the generic code.


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  https://reviews.llvm.org/D149407/new/

https://reviews.llvm.org/D149407