[PATCH] D126546: [InstCombine] decomposeSimpleLinearExpr should bail out on negative operands.

[wael yehia via Phabricator via llvm-commits]

w2yehia added inline comments.


================
Comment at: llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp:40
     OverflowingBinaryOperator *OBI = dyn_cast<OverflowingBinaryOperator>(Val);
     if (OBI && !OBI->hasNoUnsignedWrap() && !OBI->hasNoSignedWrap()) {
       Scale = 1;
----------------
nikic wrote:
> Isn't the actual bug here? The `&& !OBI->hasNoSignedWrap()` shouldn't be there. The number of elements is an unsigned value, so we should be checking for no unsigned wrap, not "either no unsigned or no signed wrap".
i'm not that familiar with the implications of (not) having `nsw`, so you are likely correct.
Does the presence of `nsw` indicate the operands of the multiplication are signed?


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D126546/new/

https://reviews.llvm.org/D126546