[llvm] [VPlan] Implement VPlan-based unit-strideness speculation (PR #182595)

[Luke Lau via llvm-commits]

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@@ -589,6 +589,13 @@ struct VPlanTransforms {
                                          VPRecipeBuilder &RecipeBuilder,
                                          VPCostContext &CostCtx);
 
+  /// \p MemOps must be updated to contain ones that haven't been processed by
+  /// the pass.
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lukel97 wrote:

I believe the MemOps comment is outdated now since we don't modify it. Can we also add a description of the transform in the comment?

Something like "Searches MemOps for strided accesses where the stride is only known at runtime and predicates the plan so the strides become unit-strided"

https://github.com/llvm/llvm-project/pull/182595