[PATCH] D94175: [VPlan] Move reduction start value creation to widenPHIRecipe.

Fri Jan 8 09:53:23 PST 2021

fhahn added a comment.

In D94175#2487083 <https://reviews.llvm.org/D94175#2487083>, @gilr wrote:

> LGTM, with a nit.
> (Seems reduction might be worth splitting widenPhiInstruction() and its own Recipe, but that's beyond the scope of this patch)
> Thanks!

Thanks Gil! Yes I think we can think about splitting them up as follow-ups.

================
Comment at: llvm/lib/Transforms/Vectorize/LoopVectorize.cpp:4587
+
+    if (RdxDesc) {
+      RecurKind RK = RdxDesc->getRecurrenceKind();
----------------
gilr wrote:
> To be on the safe side I'd check here for `Legal->isReductionVariable(P)` and assert that RdxDesc and StartV are not null inside.
I added an assertion that `Legal->isReductionVariable(P)` and  `StartV` must be true. I also added another assertion below to ensure we do not miss legal induction variables for which `RdxDesc` is not set.

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https://reviews.llvm.org/D94175