[llvm] [VPlan] Manage instruction medata in VPlan. (PR #135272)

[via llvm-commits]

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@@ -1190,28 +1190,55 @@ struct VPIRPhi : public VPIRInstruction {
 #endif
 };
 
+using MDArrayRef = ArrayRef<std::pair<unsigned, MDNode *>>;
+
+/// Helper to manage IR metadata for recipes. It filters out metadata that
+/// cannot be proagated.
+class VPWithIRMetadata {
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ayalz wrote:

"With" seems redundant here. There are IRFlags and IRMetadata, there are recipes With the former or the latter or both or none. IRFlags are modeled by relevant VPlan recipes using a nameless union which VPRecipeWithIRFlags "has", rather than inherits from. VP[IR]FlagsTy might be an appropriate name for this union, and VP[IR]Flags a name for a base class. VP[IR]Metadata may be a consistent name for a base class wrapping IRMetadata.

`VPRecipeWithMetadata` may serve as a common base class for recipes having metadata but not flags, but according to this patch these currently include only VPWidenMemoryRecipe's, so perhaps currently redundant.

`VPRecipeWithFlagsAndMetadata` may serve as a common base class for recipes having both, which according to this patch currently include { VPWidenRecipe, VPWidenCallRecipe, VPWidenIntrinsicRecipe, VPWidenCastRecipe and VPWidenSelectRecipe }.

`VPRecipeWith[IR]Flags` will then continue to serve the following subclasses of recipes having flags but no metadata: { VPInstruction(?), VPReplicateRecipe(?), VPWidenGEPRecipe, VPScalarIVStepsRecipe, VPVectorPointerRecipe, VPReverseVectorPointerRecipe,   }

https://github.com/llvm/llvm-project/pull/135272