[PATCH] D66612: [Reassoc] Small fix to support unary FNeg in NegateValue(...)

[Cameron McInally via Phabricator via llvm-commits]

cameron.mcinally marked an inline comment as done.
cameron.mcinally added inline comments.


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Comment at: llvm/lib/Transforms/Scalar/Reassociate.cpp:916
   // negation.
   BinaryOperator *NewNeg = CreateNeg(V, V->getName() + ".neg", BI, BI);
   ToRedo.insert(NewNeg);
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mcberg2017 wrote:
> You will need to revise this one too in D61675 as it will be a unary then.  Just a note to remember.
I think this one is okay. This is creating a new binary FNeg.

I'm still working out the details, but I suspect that allowing Reassociation to form binary FNegs is good (i.e. better trees). E.g.:

x + -y

can be safely transformed to:

x + (-0.0 - y)

as long as the x isn't optimized away (Sanjay showed this in another Diff). I can elaborate if anyone is interested...


Repository:
  rL LLVM

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  https://reviews.llvm.org/D66612/new/

https://reviews.llvm.org/D66612