Fix layering issue by moving AliasScopeNode from ScopedNoAliasAA.h to Metadata.h

[modimo]

Summary

@MaskRay pointed out that having Metadata.h include ScopedNoAliasAA.h introduces a layering issue. The fix is
to move the declaration of AliasScopeNode to Metadata.h which is already included by ScopedNoAliasAA.cpp and remove Metadata.h
including ScopedNoAliasAA.h

[modimo]

Fixed by https://reviews.llvm.org/rG756fa8b9be0ca3458073952495c323ba9d04036d

llvm/include/llvm/Analysis/ScopedNoAliasAA.h

 #include <memory>
 
 namespace llvm {
 
 class Function;
 class MDNode;
 class MemoryLocation;
 
-/// This is a simple wrapper around an MDNode which provides a higher-level
-/// interface by hiding the details of how alias analysis information is encoded
-/// in its operands.
-class AliasScopeNode {
-  const MDNode *Node = nullptr;
-
-public:
-  AliasScopeNode() = default;
-  explicit AliasScopeNode(const MDNode *N) : Node(N) {}
-
-  /// Get the MDNode for this AliasScopeNode.
-  const MDNode *getNode() const { return Node; }
-
-  /// Get the MDNode for this AliasScopeNode's domain.
-  const MDNode *getDomain() const {
-    if (Node->getNumOperands() < 2)
-      return nullptr;
-    return dyn_cast_or_null<MDNode>(Node->getOperand(1));
-  }
-};
-
 /// A simple AA result which uses scoped-noalias metadata to answer queries.
 class ScopedNoAliasAAResult : public AAResultBase<ScopedNoAliasAAResult> {
   friend AAResultBase<ScopedNoAliasAAResult>;
 
 public:
   /// Handle invalidation events from the new pass manager.
   ///
   /// By definition, this result is stateless and so remains valid.

llvm/include/llvm/IR/Metadata.h

#include "llvm/IR/Metadata.def"
   static MDNode *intersect(MDNode *A, MDNode *B);
   static MDNode *getMostGenericTBAA(MDNode *A, MDNode *B);
   static MDNode *getMostGenericFPMath(MDNode *A, MDNode *B);
   static MDNode *getMostGenericRange(MDNode *A, MDNode *B);
   static MDNode *getMostGenericAliasScope(MDNode *A, MDNode *B);
   static MDNode *getMostGenericAlignmentOrDereferenceable(MDNode *A, MDNode *B);
 };
 
+/// This is a simple wrapper around an MDNode which provides a higher-level
+/// interface by hiding the details of how scoped alias analysis information is
+/// encoded in its operands.
+class AliasScopeNode {
+  const MDNode *Node = nullptr;
+
+public:
+  AliasScopeNode() = default;
+  explicit AliasScopeNode(const MDNode *N) : Node(N) {}
+
+  /// Get the MDNode for this AliasScopeNode.
+  const MDNode *getNode() const { return Node; }
+
+  /// Get the MDNode for this AliasScopeNode's domain.
+  const MDNode *getDomain() const {
+    if (Node->getNumOperands() < 2)
+      return nullptr;
+    return dyn_cast_or_null<MDNode>(Node->getOperand(1));
+  }
+};
+
 /// Tuple of metadata.
 ///
 /// This is the simple \a MDNode arbitrary tuple.  Nodes are uniqued by
 /// default based on their operands.
 class MDTuple : public MDNode {
   friend class LLVMContextImpl;
   friend class MDNode;
 

llvm/lib/IR/Metadata.cpp

 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/Twine.h"
-#include "llvm/Analysis/ScopedNoAliasAA.h"
 #include "llvm/IR/Argument.h"
 #include "llvm/IR/BasicBlock.h"
 #include "llvm/IR/Constant.h"
 #include "llvm/IR/ConstantRange.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/DebugLoc.h"
 #include "llvm/IR/Function.h"