[PATCH] D146350: [InstCombine] More aggressively try and fold irem/idiv/mul into selects.

[Nikita Popov via Phabricator via llvm-commits]

nikic added inline comments.


================
Comment at: llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp:206
+             isSafeToSpeculativelyExecute(&I, Q->CxtI, Q->AC, Q->DT, TLI))
+      return false;
+  }
----------------
nikic wrote:
> Is this code in here so the case where the div is always folded away is always handled, as we're at worst going to relax to poison there and not introduce UB?
> 
> If so, I think it might be more elegant to sink this check into FoldOpIntoSelect and use the isSafeToSpeculativelyExecute variant that accepts operands, so we can check the operation that we're actually going to introduce (and thus also skip the check if we're not going to introduce one).
> and use the isSafeToSpeculativelyExecute variant that accepts operands

Well, it looks like I imagined that variant... So ignore that bit (or leave a TODO for possible future improvement) and just take the bit about only checking it if we're going to introduce an op.


Repository:
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  https://reviews.llvm.org/D146350/new/

https://reviews.llvm.org/D146350