[PATCH] D138475: [SCEVExpander] Support cost evaluation of several SCEVs with same budget

[Max Kazantsev via Phabricator via llvm-commits]

mkazantsev added inline comments.


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Comment at: llvm/include/llvm/Transforms/Utils/ScalarEvolutionExpander.h:226
+  bool isHighCostExpansion(ArrayRef<const SCEV *> Exprs, Loop *L,
+                           unsigned Budget, const TargetTransformInfo *TTI,
                            const Instruction *At) {
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mkazantsev wrote:
> lebedev.ri wrote:
> > I was thinking `Budget` should be a non-const-ref,
> > and we should just subtract the computed cost from it
> > if we return false from this function.
> > Would that be worse?
> I think it should be fine, let's try it out.
Let's leave it as is. The issue I'm seeing is that the estimate is done in terms of scaled budget, and there is no clear translation of scaled budget back into the normal one (division is lossy).




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  https://reviews.llvm.org/D138475/new/

https://reviews.llvm.org/D138475