[llvm] [NFCI][VPlan] Split initial mem-widening into a separate transformation (PR #182592)

[Luke Lau via llvm-commits]

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@@ -6252,3 +6252,59 @@ void VPlanTransforms::createPartialReductions(VPlan &Plan,
     for (const VPPartialReductionChain &Chain : Chains)
       transformToPartialReduction(Chain, CostCtx.Types, Plan, Phi);
 }
+
+void VPlanTransforms::makeMemOpWideningDecisions(VPlan &Plan, VFRange &Range,
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lukel97 wrote:

Nit, this doesn't just make the decisions but also does the widening. I'd name it just something like `widenMemOps`

https://github.com/llvm/llvm-project/pull/182592