[PATCH] D92726: Teach isKnownNonEqual how to recurse through invertable multiplies

[Nikita Popov via Phabricator via llvm-commits]

nikic added inline comments.


================
Comment at: llvm/lib/Analysis/ValueTracking.cpp:2540
+      if (!cast<BinaryOperator>(O1)->hasNoUnsignedWrap() ||
+          !cast<BinaryOperator>(O2)->hasNoUnsignedWrap())
+        break;
----------------
For completely sake, I think this should handle the nsw case as well.


================
Comment at: llvm/lib/Analysis/ValueTracking.cpp:2543
+
+      // Assume operand order has been canonicalized
+      if (O1->getOperand(0) == O2->getOperand(0) &&
----------------
With canonicalized operands, the constant can only be on the RHS.


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Comment at: llvm/test/Analysis/ValueTracking/known-non-equal.ll:169
+  %A.op = mul i8 0, %A
+  %B.op = mul i8 0, %B
+
----------------
Add `nuw` to these to make it eligible in the first place?


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Comment at: llvm/test/Analysis/ValueTracking/known-non-equal.ll:173
+  ret i1 %cmp
+}
+
----------------
We should also have a negative test with `nuw` but non-constant (and thus not known non zero) common operand.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D92726/new/

https://reviews.llvm.org/D92726