[PATCH] D152281: [Transforms][LICM] Add the ability to undo unprofitable reassociation

[Nikita Popov via Phabricator via llvm-commits]

nikic added inline comments.


================
Comment at: llvm/lib/Transforms/Scalar/LICM.cpp:2725
+    if (Use *U =
+            Ops[L.isLoopInvariant(Ops[0]) ? 0 : 1]->getSingleUndroppableUse())
+      Changes.push_back(U);
----------------
This should be `&Op->getOperandUse(Ops[L.isLoopInvariant(Ops[0]) ? 0 : 1])` or so. But I think it would be less awkward to do something like this, so you don't go back and forth between operand indices, Values and Uses:

```
if (Op->getOpcode() != Instruction::FMul) {
  if (OpNext->getOpcode() != Instruction::FMul)
    return false;
  std::swap(Op, OpNext);
}
if (!Op->hasOneUse() || !Op->hasAllowReassoc() || L.isLoopInvariant(Op))
  return false;
Use &U0 = Op->getOperandUse(0);
Use &U1 = Op->getOperandUse(1);
if (L.isLoopInvariant(U0))
  Changes.push_back(&U0);
else if (L.isLoopInvariant(U1))
  Changes.push_back(&U1);
else
  return false;
```


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D152281/new/

https://reviews.llvm.org/D152281