[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 {
+  SmallVector<std::pair<unsigned, MDNode *>> Metadata;
+
+protected:
+  VPWithIRMetadata() {}
+  VPWithIRMetadata(MDArrayRef Metadata) : Metadata(Metadata) {}
+
+  void addMetadata(MDArrayRef Metadata) {
+    append_range(this->Metadata, Metadata);
+  }
+
+public:
+  /// Add all metadata to \p V if it is an instruction.
+  void setMetadata(Value *V) const;
+
+  void addMetadata(unsigned Kind, MDNode *N) { Metadata.emplace_back(Kind, N); }
+
+  MDArrayRef getMetadata() const { return Metadata; }
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ayalz wrote:

Comment that this serves recipe cloning?

Would `transferMetadata()` be useful for cloning instead, consistent with `transferFlags()`?

Note that in contrast Instruction::getMetadata() returns a single MDNote per given kind (which is more accurately getMetadatum()...).

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