[PATCH] D132412: [InstCombine] reassociate/factor add+mul with common operand

[chenglin.bi via Phabricator via llvm-commits]

bcl5980 added inline comments.


================
Comment at: llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp:1423
+    Value *IncY = Builder.CreateAdd(Y, ConstantInt::get(I.getType(), 1));
+    return BinaryOperator::CreateMul(IncY, X);
+  }
----------------
bcl5980 wrote:
> spatel wrote:
> > Allen wrote:
> > > should we need consider the flag of NUW and NSW ?
> > I only found one case so far where we can partially propagate nuw:
> > https://alive2.llvm.org/ce/z/aGSyrK
> > Everything else seems to be illegal. Propagating the flag would be another reason to code this match explicitly rather than trying to make it work through tryFactorization().
> If we don't move it to tryFactorization, do we  need to add the similar pattern x*y - x --> (x-1) * y ?
sorry, should be x*y -x --> x * (y-1)


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D132412/new/

https://reviews.llvm.org/D132412