[PATCH] D24808: [AArch64] Avoid materializing 0.0 when generating FP CSEL

Evandro Menezes via llvm-commits llvm-commits at lists.llvm.org
Tue Oct 18 12:35:01 PDT 2016

evandro added a comment.

In https://reviews.llvm.org/D24808#573402, @rengolin wrote:

> In https://reviews.llvm.org/D24808#571590, @evandro wrote:
> > Please, see https://reviews.llvm.org/D24808#554492 and let me know if you need more information.
> That answers why not move into the DAGCombiner, not why not make it any constant, right?

I think that it answers both questions.  Again, unless the target cam perform the comparison against a constant implicit in the corresponding instruction, then this transform provides no improvement.  IOW, only if the target does not have to materialize the constant for the comparison does it make sense to not materialize it for the selection.  Otherwise, if it has to be materialzied for one, it will likely be around to be used for the other.



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