diff --git a/clang/include/clang/AST/Expr.h b/clang/include/clang/AST/Expr.h
@@ -6610,6 +6610,275 @@ class TypoExpr : public Expr {
 
 };
 
+/// This class represents BOTH the OpenMP Array Section and OpenACC 'subarray',
+/// with a boolean differentiator.
+/// OpenMP 5.0 [2.1.5, Array Sections].
+/// To specify an array section in an OpenMP construct, array subscript
+/// expressions are extended with the following syntax:
+/// \code
+/// [ lower-bound : length : stride ]
+/// [ lower-bound : length : ]
+/// [ lower-bound : length ]
+/// [ lower-bound : : stride ]
+/// [ lower-bound : : ]
+/// [ lower-bound : ]
+/// [ : length : stride ]
+/// [ : length : ]
+/// [ : length ]
+/// [ : : stride ]
+/// [ : : ]
+/// [ : ]
+/// \endcode
+/// The array section must be a subset of the original array.
+/// Array sections are allowed on multidimensional arrays. Base language array
+/// subscript expressions can be used to specify length-one dimensions of
+/// multidimensional array sections.
+/// Each of the lower-bound, length, and stride expressions if specified must be
+/// an integral type expressions of the base language. When evaluated
+/// they represent a set of integer values as follows:
+/// \code
+/// { lower-bound, lower-bound + stride, lower-bound + 2 * stride,... ,
+/// lower-bound + ((length - 1) * stride) }
+/// \endcode
+/// The lower-bound and length must evaluate to non-negative integers.
+/// The stride must evaluate to a positive integer.
+/// When the size of the array dimension is not known, the length must be
+/// specified explicitly.
+/// When the stride is absent it defaults to 1.
+/// When the length is absent it defaults to ⌈(size − lower-bound)/stride⌉,
+/// where size is the size of the array dimension. When the lower-bound is
+/// absent it defaults to 0.
+///
+///
+/// OpenACC 3.3 [2.7.1 Data Specification in Data Clauses]
+/// In C and C++, a subarray is an array name followed by an extended array
+/// range specification in brackets, with start and length, such as
+///
+/// AA[2:n]
+///
+/// If the lower bound is missing, zero is used. If the length is missing and
+/// the array has known size, the size of the array is used; otherwise the
+/// length is required. The subarray AA[2:n] means elements AA[2], AA[3], . . .
+/// , AA[2+n-1]. In C and C++, a two dimensional array may be declared in at
+/// least four ways:
+///
+/// -Statically-sized array: float AA[100][200];
+/// -Pointer to statically sized rows: typedef float row[200]; row* BB;
+/// -Statically-sized array of pointers: float* CC[200];
+/// -Pointer to pointers: float** DD;
+///
+/// Each dimension may be statically sized, or a pointer to dynamically
+/// allocated memory. Each of these may be included in a data clause using
+/// subarray notation to specify a rectangular array:
+///
+/// -AA[2:n][0:200]
+/// -BB[2:n][0:m]
+/// -CC[2:n][0:m]
+/// -DD[2:n][0:m]
+///
+/// Multidimensional rectangular subarrays in C and C++ may be specified for any
+/// array with any combination of statically-sized or dynamically-allocated
+/// dimensions. For statically sized dimensions, all dimensions except the first
+/// must specify the whole extent to preserve the contiguous data restriction,
+/// discussed below. For dynamically allocated dimensions, the implementation
+/// will allocate pointers in device memory corresponding to the pointers in
+/// local memory and will fill in those pointers as appropriate.
+///
+/// In Fortran, a subarray is an array name followed by a comma-separated list
+/// of range specifications in parentheses, with lower and upper bound
+/// subscripts, such as
+///
+/// arr(1:high,low:100)
+///
+/// If either the lower or upper bounds are missing, the declared or allocated
+/// bounds of the array, if known, are used. All dimensions except the last must
+/// specify the whole extent, to preserve the contiguous data restriction,
+/// discussed below.
+///
+/// Restrictions
+///
+/// -In Fortran, the upper bound for the last dimension of an assumed-size dummy
+/// array must be specified.
+///
+/// -In C and C++, the length for dynamically allocated dimensions of an array
+/// must be explicitly specified.
+///
+/// -In C and C++, modifying pointers in pointer arrays during the data
+/// lifetime, either on the host or on the device, may result in undefined
+/// behavior.
+///
+/// -If a subarray  appears in a data clause, the implementation may choose to
+/// allocate memory for only that subarray on the accelerator.
+///
+/// -In Fortran, array pointers may appear, but pointer association is not
+/// preserved in device memory.
+///
+/// -Any array or subarray in a data clause, including Fortran array pointers,
+/// must be a contiguous section of memory, except for dynamic multidimensional
+/// C arrays.
+///
+/// -In C and C++, if a variable or array of composite type appears, all the
+/// data members of the struct or class are allocated and copied, as
+/// appropriate. If a composite member is a pointer type, the data addressed by
+/// that pointer are not implicitly copied.
+///
+/// -In Fortran, if a variable or array of composite type appears, all the
+/// members of that derived type are allocated and copied, as appropriate. If
+/// any member has the allocatable or pointer attribute, the data accessed
+/// through that member are not copied.
+///
+/// -If an expression is used in a subscript or subarray expression in a clause
+/// on a data construct, the same value is used when copying data at the end of
+/// the data region, even if the values of variables in the expression change
+/// during the data region.
+class ArraySectionExpr : public Expr {
+  friend class ASTStmtReader;
+  friend class ASTStmtWriter;
+
+public:
+  enum ArraySectionType { OMPArraySection, OpenACCArraySection };
+
+private:
+  enum {
+    BASE,
+    LOWER_BOUND,
+    LENGTH,
+    STRIDE,
+    END_EXPR,
+    OPENACC_END_EXPR = STRIDE
+  };
+
+  ArraySectionType ASType = OMPArraySection;
+  Stmt *SubExprs[END_EXPR] = {nullptr};
+  SourceLocation ColonLocFirst;
+  SourceLocation ColonLocSecond;
+  SourceLocation RBracketLoc;
+
+public:
+  // Constructor for OMP array sections, which include a 'stride'.
+  ArraySectionExpr(Expr *Base, Expr *LowerBound, Expr *Length, Expr *Stride,
+                   QualType Type, ExprValueKind VK, ExprObjectKind OK,
+                   SourceLocation ColonLocFirst, SourceLocation ColonLocSecond,
+                   SourceLocation RBracketLoc)
+      : Expr(ArraySectionExprClass, Type, VK, OK), ASType(OMPArraySection),
+        ColonLocFirst(ColonLocFirst), ColonLocSecond(ColonLocSecond),
+        RBracketLoc(RBracketLoc) {
+    setBase(Base);
+    setLowerBound(LowerBound);
+    setLength(Length);
+    setStride(Stride);
+    setDependence(computeDependence(this));
+  }
+
+  // Constructor for OpenACC sub-arrays, which do not permit a 'stride'.
+  ArraySectionExpr(Expr *Base, Expr *LowerBound, Expr *Length, QualType Type,
+                   ExprValueKind VK, ExprObjectKind OK, SourceLocation ColonLoc,
+                   SourceLocation RBracketLoc)
+      : Expr(ArraySectionExprClass, Type, VK, OK), ASType(OpenACCArraySection),
+        ColonLocFirst(ColonLoc), RBracketLoc(RBracketLoc) {
+    setBase(Base);
+    setLowerBound(LowerBound);
+    setLength(Length);
+    setDependence(computeDependence(this));
+  }
+
+  /// Create an empty array section expression.
+  explicit ArraySectionExpr(EmptyShell Shell)
+      : Expr(ArraySectionExprClass, Shell) {}
+
+  /// Return original type of the base expression for array section.
+  static QualType getBaseOriginalType(const Expr *Base);
+
+  static bool classof(const Stmt *T) {
+    return T->getStmtClass() == ArraySectionExprClass;
+  }
+
+  bool isOMPArraySection() const { return ASType == OMPArraySection; }
+  bool isOpenACCArraySection() const { return ASType == OpenACCArraySection; }
+
+  /// Get base of the array section.
+  Expr *getBase() { return cast<Expr>(SubExprs[BASE]); }
+  const Expr *getBase() const { return cast<Expr>(SubExprs[BASE]); }
+
+  /// Get lower bound of array section.
+  Expr *getLowerBound() { return cast_or_null<Expr>(SubExprs[LOWER_BOUND]); }
+  const Expr *getLowerBound() const {
+    return cast_or_null<Expr>(SubExprs[LOWER_BOUND]);
+  }
+
+  /// Get length of array section.
+  Expr *getLength() { return cast_or_null<Expr>(SubExprs[LENGTH]); }
+  const Expr *getLength() const { return cast_or_null<Expr>(SubExprs[LENGTH]); }
+
+  /// Get stride of array section.
+  Expr *getStride() {
+    assert(ASType != OpenACCArraySection &&
+           "Stride not valid in OpenACC subarrays");
+    return cast_or_null<Expr>(SubExprs[STRIDE]);
+  }
+
+  const Expr *getStride() const {
+    assert(ASType != OpenACCArraySection &&
+           "Stride not valid in OpenACC subarrays");
+    return cast_or_null<Expr>(SubExprs[STRIDE]);
+  }
+
+  SourceLocation getBeginLoc() const LLVM_READONLY {
+    return getBase()->getBeginLoc();
+  }
+  SourceLocation getEndLoc() const LLVM_READONLY { return RBracketLoc; }
+
+  SourceLocation getColonLocFirst() const { return ColonLocFirst; }
+  SourceLocation getColonLocSecond() const {
+    assert(ASType != OpenACCArraySection &&
+           "second colon for stride not valid in OpenACC subarrays");
+    return ColonLocSecond;
+  }
+  SourceLocation getRBracketLoc() const { return RBracketLoc; }
+
+  SourceLocation getExprLoc() const LLVM_READONLY {
+    return getBase()->getExprLoc();
+  }
+
+  child_range children() {
+    return child_range(
+        &SubExprs[BASE],
+        &SubExprs[ASType == OMPArraySection ? END_EXPR : OPENACC_END_EXPR]);
+  }
+
+  const_child_range children() const {
+    return const_child_range(
+        &SubExprs[BASE],
+        &SubExprs[ASType == OMPArraySection ? END_EXPR : OPENACC_END_EXPR]);
+  }
+
+private:
+  /// Set base of the array section.
+  void setBase(Expr *E) { SubExprs[BASE] = E; }
+
+  /// Set lower bound of the array section.
+  void setLowerBound(Expr *E) { SubExprs[LOWER_BOUND] = E; }
+
+  /// Set length of the array section.
+  void setLength(Expr *E) { SubExprs[LENGTH] = E; }
+
+  /// Set length of the array section.
+  void setStride(Expr *E) {
+    assert(ASType != OpenACCArraySection &&
+           "Stride not valid in OpenACC subarrays");
+    SubExprs[STRIDE] = E;
+  }
+
+  void setColonLocFirst(SourceLocation L) { ColonLocFirst = L; }
+
+  void setColonLocSecond(SourceLocation L) {
+    assert(ASType != OpenACCArraySection &&
+           "second colon for stride not valid in OpenACC subarrays");
+    ColonLocSecond = L;
+  }
+  void setRBracketLoc(SourceLocation L) { RBracketLoc = L; }
+};
+
 /// Frontend produces RecoveryExprs on semantic errors that prevent creating
 /// other well-formed expressions. E.g. when type-checking of a binary operator
 /// fails, we cannot produce a BinaryOperator expression. Instead, we can choose

diff --git a/clang/include/clang/AST/ExprOpenMP.h b/clang/include/clang/AST/ExprOpenMP.h
@@ -17,130 +17,6 @@
 #include "clang/AST/Expr.h"
 
 namespace clang {
-/// OpenMP 5.0 [2.1.5, Array Sections].
-/// To specify an array section in an OpenMP construct, array subscript
-/// expressions are extended with the following syntax:
-/// \code
-/// [ lower-bound : length : stride ]
-/// [ lower-bound : length : ]
-/// [ lower-bound : length ]
-/// [ lower-bound : : stride ]
-/// [ lower-bound : : ]
-/// [ lower-bound : ]
-/// [ : length : stride ]
-/// [ : length : ]
-/// [ : length ]
-/// [ : : stride ]
-/// [ : : ]
-/// [ : ]
-/// \endcode
-/// The array section must be a subset of the original array.
-/// Array sections are allowed on multidimensional arrays. Base language array
-/// subscript expressions can be used to specify length-one dimensions of
-/// multidimensional array sections.
-/// Each of the lower-bound, length, and stride expressions if specified must be
-/// an integral type expressions of the base language. When evaluated
-/// they represent a set of integer values as follows:
-/// \code
-/// { lower-bound, lower-bound + stride, lower-bound + 2 * stride,... ,
-/// lower-bound + ((length - 1) * stride) }
-/// \endcode
-/// The lower-bound and length must evaluate to non-negative integers.
-/// The stride must evaluate to a positive integer.
-/// When the size of the array dimension is not known, the length must be
-/// specified explicitly.
-/// When the stride is absent it defaults to 1.
-/// When the length is absent it defaults to ⌈(size − lower-bound)/stride⌉,
-/// where size is the size of the array dimension. When the lower-bound is
-/// absent it defaults to 0.
-class OMPArraySectionExpr : public Expr {
-  enum { BASE, LOWER_BOUND, LENGTH, STRIDE, END_EXPR };
-  Stmt *SubExprs[END_EXPR];
-  SourceLocation ColonLocFirst;
-  SourceLocation ColonLocSecond;
-  SourceLocation RBracketLoc;
-
-public:
-  OMPArraySectionExpr(Expr *Base, Expr *LowerBound, Expr *Length, Expr *Stride,
-                      QualType Type, ExprValueKind VK, ExprObjectKind OK,
-                      SourceLocation ColonLocFirst,
-                      SourceLocation ColonLocSecond, SourceLocation RBracketLoc)
-      : Expr(OMPArraySectionExprClass, Type, VK, OK),
-        ColonLocFirst(ColonLocFirst), ColonLocSecond(ColonLocSecond),
-        RBracketLoc(RBracketLoc) {
-    SubExprs[BASE] = Base;
-    SubExprs[LOWER_BOUND] = LowerBound;
-    SubExprs[LENGTH] = Length;
-    SubExprs[STRIDE] = Stride;
-    setDependence(computeDependence(this));
-  }
-
-  /// Create an empty array section expression.
-  explicit OMPArraySectionExpr(EmptyShell Shell)
-      : Expr(OMPArraySectionExprClass, Shell) {}
-
-  /// An array section can be written only as Base[LowerBound:Length].
-
-  /// Get base of the array section.
-  Expr *getBase() { return cast<Expr>(SubExprs[BASE]); }
-  const Expr *getBase() const { return cast<Expr>(SubExprs[BASE]); }
-  /// Set base of the array section.
-  void setBase(Expr *E) { SubExprs[BASE] = E; }
-
-  /// Return original type of the base expression for array section.
-  static QualType getBaseOriginalType(const Expr *Base);
-
-  /// Get lower bound of array section.
-  Expr *getLowerBound() { return cast_or_null<Expr>(SubExprs[LOWER_BOUND]); }
-  const Expr *getLowerBound() const {
-    return cast_or_null<Expr>(SubExprs[LOWER_BOUND]);
-  }
-  /// Set lower bound of the array section.
-  void setLowerBound(Expr *E) { SubExprs[LOWER_BOUND] = E; }
-
-  /// Get length of array section.
-  Expr *getLength() { return cast_or_null<Expr>(SubExprs[LENGTH]); }
-  const Expr *getLength() const { return cast_or_null<Expr>(SubExprs[LENGTH]); }
-  /// Set length of the array section.
-  void setLength(Expr *E) { SubExprs[LENGTH] = E; }
-
-  /// Get stride of array section.
-  Expr *getStride() { return cast_or_null<Expr>(SubExprs[STRIDE]); }
-  const Expr *getStride() const { return cast_or_null<Expr>(SubExprs[STRIDE]); }
-  /// Set length of the array section.
-  void setStride(Expr *E) { SubExprs[STRIDE] = E; }
-
-  SourceLocation getBeginLoc() const LLVM_READONLY {
-    return getBase()->getBeginLoc();
-  }
-  SourceLocation getEndLoc() const LLVM_READONLY { return RBracketLoc; }
-
-  SourceLocation getColonLocFirst() const { return ColonLocFirst; }
-  void setColonLocFirst(SourceLocation L) { ColonLocFirst = L; }
-
-  SourceLocation getColonLocSecond() const { return ColonLocSecond; }
-  void setColonLocSecond(SourceLocation L) { ColonLocSecond = L; }
-
-  SourceLocation getRBracketLoc() const { return RBracketLoc; }
-  void setRBracketLoc(SourceLocation L) { RBracketLoc = L; }
-
-  SourceLocation getExprLoc() const LLVM_READONLY {
-    return getBase()->getExprLoc();
-  }
-
-  static bool classof(const Stmt *T) {
-    return T->getStmtClass() == OMPArraySectionExprClass;
-  }
-
-  child_range children() {
-    return child_range(&SubExprs[BASE], &SubExprs[END_EXPR]);
-  }
-
-  const_child_range children() const {
-    return const_child_range(&SubExprs[BASE], &SubExprs[END_EXPR]);
-  }
-};
-
 /// An explicit cast in C or a C-style cast in C++, which uses the syntax
 /// ([s1][s2]...[sn])expr. For example: @c ([3][3])f.
 class OMPArrayShapingExpr final

diff --git a/clang/include/clang/AST/ExternalASTSource.h b/clang/include/clang/AST/ExternalASTSource.h
@@ -99,7 +99,7 @@ class ExternalASTSource : public RefCountedBase<ExternalASTSource> {
   /// passes back decl sets as VisibleDeclaration objects.
   ///
   /// The default implementation of this method is a no-op.
-  virtual Decl *GetExternalDecl(Decl::DeclID ID);
+  virtual Decl *GetExternalDecl(GlobalDeclID ID);
 
   /// Resolve a selector ID into a selector.
   ///
@@ -375,7 +375,7 @@ struct LazyOffsetPtr {
     if (isOffset()) {
       assert(Source &&
              "Cannot deserialize a lazy pointer without an AST source");
-      Ptr = reinterpret_cast<uint64_t>((Source->*Get)(Ptr >> 1));
+      Ptr = reinterpret_cast<uint64_t>((Source->*Get)(OffsT(Ptr >> 1)));
     }
     return reinterpret_cast<T*>(Ptr);
   }
@@ -579,7 +579,7 @@ using LazyDeclStmtPtr =
 
 /// A lazy pointer to a declaration.
 using LazyDeclPtr =
-    LazyOffsetPtr<Decl, Decl::DeclID, &ExternalASTSource::GetExternalDecl>;
+    LazyOffsetPtr<Decl, GlobalDeclID, &ExternalASTSource::GetExternalDecl>;
 
 /// A lazy pointer to a set of CXXCtorInitializers.
 using LazyCXXCtorInitializersPtr =

diff --git a/clang/include/clang/AST/RecursiveASTVisitor.h b/clang/include/clang/AST/RecursiveASTVisitor.h
@@ -2740,7 +2740,7 @@ DEF_TRAVERSE_STMT(CXXMemberCallExpr, {})
 DEF_TRAVERSE_STMT(AddrLabelExpr, {})
 DEF_TRAVERSE_STMT(ArraySubscriptExpr, {})
 DEF_TRAVERSE_STMT(MatrixSubscriptExpr, {})
-DEF_TRAVERSE_STMT(OMPArraySectionExpr, {})
+DEF_TRAVERSE_STMT(ArraySectionExpr, {})
 DEF_TRAVERSE_STMT(OMPArrayShapingExpr, {})
 DEF_TRAVERSE_STMT(OMPIteratorExpr, {})
 

diff --git a/clang/include/clang/Basic/DiagnosticFrontendKinds.td b/clang/include/clang/Basic/DiagnosticFrontendKinds.td
@@ -370,4 +370,7 @@ def warn_missing_symbol_graph_dir : Warning<
   "Missing symbol graph output directory, defaulting to working directory">,
   InGroup<ExtractAPIMisuse>;
 
+def err_ast_action_on_llvm_ir : Error<
+  "cannot apply AST actions to LLVM IR file '%0'">,
+  DefaultFatal;
 }
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -11161,7 +11161,7 @@ def err_omp_declare_mapper_redefinition : Error<
   "redefinition of user-defined mapper for type %0 with name %1">;
 def err_omp_invalid_mapper: Error<
   "cannot find a valid user-defined mapper for type %0 with name %1">;
-def err_omp_array_section_use : Error<"OpenMP array section is not allowed here">;
+def err_array_section_use : Error<"%select{OpenACC sub-array|OpenMP array section}0 is not allowed here">;
 def err_omp_array_shaping_use : Error<"OpenMP array shaping operation is not allowed here">;
 def err_omp_iterator_use : Error<"OpenMP iterator is not allowed here">;
 def err_omp_typecheck_section_value : Error<

diff --git a/clang/include/clang/Basic/FileManager.h b/clang/include/clang/Basic/FileManager.h
@@ -114,6 +114,12 @@ class FileManager : public RefCountedBase<FileManager> {
   ///
   unsigned NextFileUID;
 
+  /// Statistics gathered during the lifetime of the FileManager.
+  unsigned NumDirLookups = 0;
+  unsigned NumFileLookups = 0;
+  unsigned NumDirCacheMisses = 0;
+  unsigned NumFileCacheMisses = 0;
+
   // Caching.
   std::unique_ptr<FileSystemStatCache> StatCache;
 
@@ -341,6 +347,10 @@ class FileManager : public RefCountedBase<FileManager> {
 
 public:
   void PrintStats() const;
+
+  /// Import statistics from a child FileManager and add them to this current
+  /// FileManager.
+  void AddStats(const FileManager &Other);
 };
 
 } // end namespace clang

diff --git a/clang/include/clang/Basic/StmtNodes.td b/clang/include/clang/Basic/StmtNodes.td
@@ -71,7 +71,7 @@ def OffsetOfExpr : StmtNode<Expr>;
 def UnaryExprOrTypeTraitExpr : StmtNode<Expr>;
 def ArraySubscriptExpr : StmtNode<Expr>;
 def MatrixSubscriptExpr : StmtNode<Expr>;
-def OMPArraySectionExpr : StmtNode<Expr>;
+def ArraySectionExpr : StmtNode<Expr>;
 def OMPIteratorExpr : StmtNode<Expr>;
 def CallExpr : StmtNode<Expr>;
 def MemberExpr : StmtNode<Expr>;

diff --git a/clang/include/clang/CIR/CMakeLists.txt b/clang/include/clang/CIR/CMakeLists.txt
@@ -0,0 +1,6 @@
+set(MLIR_INCLUDE_DIR ${LLVM_MAIN_SRC_DIR}/../mlir/include ) # --includedir
+set(MLIR_TABLEGEN_OUTPUT_DIR ${CMAKE_BINARY_DIR}/tools/mlir/include)
+include_directories(${MLIR_INCLUDE_DIR})
+include_directories(${MLIR_TABLEGEN_OUTPUT_DIR})
+
+add_subdirectory(Dialect)
diff --git a/clang/include/clang/CIR/Dialect/CMakeLists.txt b/clang/include/clang/CIR/Dialect/CMakeLists.txt
@@ -0,0 +1 @@
+add_subdirectory(IR)
diff --git a/clang/include/clang/CIR/Dialect/IR/CIRDialect.h b/clang/include/clang/CIR/Dialect/IR/CIRDialect.h
@@ -0,0 +1,16 @@
+//===- CIRDialect.h - CIR dialect -------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file declares the CIR dialect.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_CIR_DIALECT_IR_CIRDIALECT_H
+#define LLVM_CLANG_CIR_DIALECT_IR_CIRDIALECT_H
+
+#endif // LLVM_CLANG_CIR_DIALECT_IR_CIRDIALECT_H
diff --git a/clang/include/clang/CIR/Dialect/IR/CIRDialect.td b/clang/include/clang/CIR/Dialect/IR/CIRDialect.td
@@ -0,0 +1,44 @@
+//===- CIRDialect.td - CIR dialect -------------------------*- tablegen -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file declares the CIR dialect.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_CIR_DIALECT_IR_CIRDIALECT
+#define LLVM_CLANG_CIR_DIALECT_IR_CIRDIALECT
+
+include "mlir/IR/OpBase.td"
+
+def CIR_Dialect : Dialect {
+  let name = "cir";
+
+  // A short one-line summary of our dialect.
+  let summary = "A high-level dialect for analyzing and optimizing Clang "
+                "supported languages";
+
+  let cppNamespace = "::mlir::cir";
+
+  let useDefaultAttributePrinterParser = 0;
+  let useDefaultTypePrinterParser = 0;
+
+  let extraClassDeclaration = [{
+    void registerAttributes();
+    void registerTypes();
+
+    Type parseType(DialectAsmParser &parser) const override;
+    void printType(Type type, DialectAsmPrinter &printer) const override;
+
+    Attribute parseAttribute(DialectAsmParser &parser,
+                             Type type) const override;
+
+    void printAttribute(Attribute attr, DialectAsmPrinter &os) const override;
+  }];
+}
+
+#endif // LLVM_CLANG_CIR_DIALECT_IR_CIRDIALECT
diff --git a/clang/include/clang/CIR/Dialect/IR/CIROps.td b/clang/include/clang/CIR/Dialect/IR/CIROps.td
@@ -0,0 +1,19 @@
+//===-- CIROps.td - CIR dialect definition -----------------*- tablegen -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Definition of the CIR dialect
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_CIR_DIALECT_IR_CIROPS
+#define LLVM_CLANG_CIR_DIALECT_IR_CIROPS
+
+include "clang/CIR/Dialect/IR/CIRDialect.td"
+
+#endif // LLVM_CLANG_CIR_DIALECT_IR_CIROPS
diff --git a/clang/include/clang/CIR/Dialect/IR/CMakeLists.txt b/clang/include/clang/CIR/Dialect/IR/CMakeLists.txt
@@ -0,0 +1,16 @@
+# This replicates part of the add_mlir_dialect cmake function from MLIR that
+# cannot be used here. This happens because it expects to be run inside MLIR
+# directory which is not the case for CIR (and also FIR, both have similar
+# workarounds).
+
+# Equivalent to add_mlir_dialect(CIROps cir)
+set(LLVM_TARGET_DEFINITIONS CIROps.td)
+mlir_tablegen(CIROps.h.inc -gen-op-decls)
+mlir_tablegen(CIROps.cpp.inc -gen-op-defs)
+mlir_tablegen(CIROpsTypes.h.inc -gen-typedef-decls)
+mlir_tablegen(CIROpsTypes.cpp.inc -gen-typedef-defs)
+mlir_tablegen(CIROpsDialect.h.inc -gen-dialect-decls)
+mlir_tablegen(CIROpsDialect.cpp.inc -gen-dialect-defs)
+add_public_tablegen_target(MLIRCIROpsIncGen)
+add_dependencies(mlir-headers MLIRCIROpsIncGen)
+
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
@@ -2615,6 +2615,11 @@ defm protect_parens : BoolFOption<"protect-parens",
           "floating-point expressions are evaluated">,
   NegFlag<SetFalse>>;
 
+defm daz_ftz : SimpleMFlag<"daz-ftz",
+  "Globally set", "Do not globally set",
+  " the denormals-are-zero (DAZ) and flush-to-zero (FTZ) bits in the "
+  "floating-point control register on program startup">;
+
 def ffor_scope : Flag<["-"], "ffor-scope">, Group<f_Group>;
 def fno_for_scope : Flag<["-"], "fno-for-scope">, Group<f_Group>;
 

diff --git a/clang/include/clang/Frontend/ASTUnit.h b/clang/include/clang/Frontend/ASTUnit.h
@@ -241,7 +241,7 @@ class ASTUnit {
 
   /// A list of the serialization ID numbers for each of the top-level
   /// declarations parsed within the precompiled preamble.
-  std::vector<serialization::DeclID> TopLevelDeclsInPreamble;
+  std::vector<LocalDeclID> TopLevelDeclsInPreamble;
 
   /// Whether we should be caching code-completion results.
   bool ShouldCacheCodeCompletionResults : 1;

diff --git a/clang/include/clang/Frontend/MultiplexConsumer.h b/clang/include/clang/Frontend/MultiplexConsumer.h
@@ -35,7 +35,7 @@ class MultiplexASTDeserializationListener : public ASTDeserializationListener {
   void IdentifierRead(serialization::IdentID ID, IdentifierInfo *II) override;
   void MacroRead(serialization::MacroID ID, MacroInfo *MI) override;
   void TypeRead(serialization::TypeIdx Idx, QualType T) override;
-  void DeclRead(serialization::DeclID ID, const Decl *D) override;
+  void DeclRead(GlobalDeclID ID, const Decl *D) override;
   void SelectorRead(serialization::SelectorID iD, Selector Sel) override;
   void MacroDefinitionRead(serialization::PreprocessedEntityID,
                            MacroDefinitionRecord *MD) override;

diff --git a/clang/include/clang/Sema/MultiplexExternalSemaSource.h b/clang/include/clang/Sema/MultiplexExternalSemaSource.h
@@ -65,7 +65,7 @@ class MultiplexExternalSemaSource : public ExternalSemaSource {
 
   /// Resolve a declaration ID into a declaration, potentially
   /// building a new declaration.
-  Decl *GetExternalDecl(Decl::DeclID ID) override;
+  Decl *GetExternalDecl(GlobalDeclID ID) override;
 
   /// Complete the redeclaration chain if it's been extended since the
   /// previous generation of the AST source.

diff --git a/clang/include/clang/Sema/SemaOpenACC.h b/clang/include/clang/Sema/SemaOpenACC.h
@@ -193,6 +193,12 @@ class SemaOpenACC : public SemaBase {
   /// conversions and diagnostics to 'int'.
   ExprResult ActOnIntExpr(OpenACCDirectiveKind DK, OpenACCClauseKind CK,
                           SourceLocation Loc, Expr *IntExpr);
+
+  /// Checks and creates an Array Section used in an OpenACC construct/clause.
+  ExprResult ActOnArraySectionExpr(Expr *Base, SourceLocation LBLoc,
+                                   Expr *LowerBound,
+                                   SourceLocation ColonLocFirst, Expr *Length,
+                                   SourceLocation RBLoc);
 };
 
 } // namespace clang

diff --git a/clang/include/clang/Serialization/ASTBitCodes.h b/clang/include/clang/Serialization/ASTBitCodes.h
@@ -17,6 +17,7 @@
 #ifndef LLVM_CLANG_SERIALIZATION_ASTBITCODES_H
 #define LLVM_CLANG_SERIALIZATION_ASTBITCODES_H
 
+#include "clang/AST/DeclID.h"
 #include "clang/AST/DeclarationName.h"
 #include "clang/AST/Type.h"
 #include "clang/Basic/IdentifierTable.h"
@@ -59,91 +60,9 @@ const unsigned VERSION_MINOR = 1;
 /// and start at 1. 0 is reserved for NULL.
 using IdentifierID = uint32_t;
 
-/// An ID number that refers to a declaration in an AST file.
-///
-/// The ID numbers of declarations are consecutive (in order of
-/// discovery), with values below NUM_PREDEF_DECL_IDS being reserved.
-/// At the start of a chain of precompiled headers, declaration ID 1 is
-/// used for the translation unit declaration.
-///
-/// FIXME: Merge with Decl::DeclID
-using DeclID = uint32_t;
-
-class LocalDeclID {
-public:
-  explicit LocalDeclID(DeclID ID) : ID(ID) {}
-
-  DeclID get() const { return ID; }
-
-private:
-  DeclID ID;
-};
-
-/// Wrapper class for DeclID. This is helpful to not mix the use of LocalDeclID
-/// and GlobalDeclID to improve the type safety.
-class GlobalDeclID {
-public:
-  GlobalDeclID() : ID(0) {}
-  explicit GlobalDeclID(DeclID ID) : ID(ID) {}
-
-  DeclID get() const { return ID; }
-
-  explicit operator DeclID() const { return ID; }
-
-  friend bool operator==(const GlobalDeclID &LHS, const GlobalDeclID &RHS) {
-    return LHS.ID == RHS.ID;
-  }
-  friend bool operator!=(const GlobalDeclID &LHS, const GlobalDeclID &RHS) {
-    return LHS.ID != RHS.ID;
-  }
-  // We may sort the global decl ID.
-  friend bool operator<(const GlobalDeclID &LHS, const GlobalDeclID &RHS) {
-    return LHS.ID < RHS.ID;
-  }
-  friend bool operator>(const GlobalDeclID &LHS, const GlobalDeclID &RHS) {
-    return LHS.ID > RHS.ID;
-  }
-  friend bool operator<=(const GlobalDeclID &LHS, const GlobalDeclID &RHS) {
-    return LHS.ID <= RHS.ID;
-  }
-  friend bool operator>=(const GlobalDeclID &LHS, const GlobalDeclID &RHS) {
-    return LHS.ID >= RHS.ID;
-  }
-
-private:
-  DeclID ID;
-};
-
-/// A helper iterator adaptor to convert the iterators to `SmallVector<DeclID>`
-/// to the iterators to `SmallVector<GlobalDeclID>`.
-class GlobalDeclIDIterator
-    : public llvm::iterator_adaptor_base<GlobalDeclIDIterator, const DeclID *,
-                                         std::forward_iterator_tag,
-                                         GlobalDeclID> {
-public:
-  GlobalDeclIDIterator() : iterator_adaptor_base(nullptr) {}
-
-  GlobalDeclIDIterator(const DeclID *ID) : iterator_adaptor_base(ID) {}
-
-  value_type operator*() const { return GlobalDeclID(*I); }
-
-  bool operator==(const GlobalDeclIDIterator &RHS) const { return I == RHS.I; }
-};
-
-/// A helper iterator adaptor to convert the iterators to
-/// `SmallVector<GlobalDeclID>` to the iterators to `SmallVector<DeclID>`.
-class DeclIDIterator
-    : public llvm::iterator_adaptor_base<DeclIDIterator, const GlobalDeclID *,
-                                         std::forward_iterator_tag, DeclID> {
-public:
-  DeclIDIterator() : iterator_adaptor_base(nullptr) {}
-
-  DeclIDIterator(const GlobalDeclID *ID) : iterator_adaptor_base(ID) {}
-
-  value_type operator*() const { return DeclID(*I); }
-
-  bool operator==(const DeclIDIterator &RHS) const { return I == RHS.I; }
-};
+/// An ID number that refers to a declaration in an AST file. See the comments
+/// in DeclIDBase for details.
+using DeclID = DeclIDBase::DeclID;
 
 /// An ID number that refers to a type in an AST file.
 ///
@@ -1054,8 +973,8 @@ enum PredefinedTypeIDs {
   /// OpenCL reserve_id type.
   PREDEF_TYPE_RESERVE_ID_ID = 41,
 
-  /// The placeholder type for OpenMP array section.
-  PREDEF_TYPE_OMP_ARRAY_SECTION = 42,
+  /// The placeholder type for an array section.
+  PREDEF_TYPE_ARRAY_SECTION = 42,
 
   /// The '__float128' type
   PREDEF_TYPE_FLOAT128_ID = 43,
@@ -1238,74 +1157,6 @@ enum SpecialTypeIDs {
 /// The number of special type IDs.
 const unsigned NumSpecialTypeIDs = 8;
 
-/// Predefined declaration IDs.
-///
-/// These declaration IDs correspond to predefined declarations in the AST
-/// context, such as the NULL declaration ID. Such declarations are never
-/// actually serialized, since they will be built by the AST context when
-/// it is created.
-enum PredefinedDeclIDs {
-  /// The NULL declaration.
-  PREDEF_DECL_NULL_ID = 0,
-
-  /// The translation unit.
-  PREDEF_DECL_TRANSLATION_UNIT_ID = 1,
-
-  /// The Objective-C 'id' type.
-  PREDEF_DECL_OBJC_ID_ID = 2,
-
-  /// The Objective-C 'SEL' type.
-  PREDEF_DECL_OBJC_SEL_ID = 3,
-
-  /// The Objective-C 'Class' type.
-  PREDEF_DECL_OBJC_CLASS_ID = 4,
-
-  /// The Objective-C 'Protocol' type.
-  PREDEF_DECL_OBJC_PROTOCOL_ID = 5,
-
-  /// The signed 128-bit integer type.
-  PREDEF_DECL_INT_128_ID = 6,
-
-  /// The unsigned 128-bit integer type.
-  PREDEF_DECL_UNSIGNED_INT_128_ID = 7,
-
-  /// The internal 'instancetype' typedef.
-  PREDEF_DECL_OBJC_INSTANCETYPE_ID = 8,
-
-  /// The internal '__builtin_va_list' typedef.
-  PREDEF_DECL_BUILTIN_VA_LIST_ID = 9,
-
-  /// The internal '__va_list_tag' struct, if any.
-  PREDEF_DECL_VA_LIST_TAG = 10,
-
-  /// The internal '__builtin_ms_va_list' typedef.
-  PREDEF_DECL_BUILTIN_MS_VA_LIST_ID = 11,
-
-  /// The predeclared '_GUID' struct.
-  PREDEF_DECL_BUILTIN_MS_GUID_ID = 12,
-
-  /// The extern "C" context.
-  PREDEF_DECL_EXTERN_C_CONTEXT_ID = 13,
-
-  /// The internal '__make_integer_seq' template.
-  PREDEF_DECL_MAKE_INTEGER_SEQ_ID = 14,
-
-  /// The internal '__NSConstantString' typedef.
-  PREDEF_DECL_CF_CONSTANT_STRING_ID = 15,
-
-  /// The internal '__NSConstantString' tag type.
-  PREDEF_DECL_CF_CONSTANT_STRING_TAG_ID = 16,
-
-  /// The internal '__type_pack_element' template.
-  PREDEF_DECL_TYPE_PACK_ELEMENT_ID = 17,
-};
-
-/// The number of declaration IDs that are predefined.
-///
-/// For more information about predefined declarations, see the
-/// \c PredefinedDeclIDs type and the PREDEF_DECL_*_ID constants.
-const unsigned int NUM_PREDEF_DECL_IDS = 18;
-
 /// Record of updates for a declaration that was modified after
 /// being deserialized. This can occur within DECLTYPES_BLOCK_ID.
 const unsigned int DECL_UPDATES = 49;
@@ -2075,7 +1926,7 @@ enum StmtCode {
   STMT_OMP_TARGET_TEAMS_GENERIC_LOOP_DIRECTIVE,
   STMT_OMP_PARALLEL_GENERIC_LOOP_DIRECTIVE,
   STMT_OMP_TARGET_PARALLEL_GENERIC_LOOP_DIRECTIVE,
-  EXPR_OMP_ARRAY_SECTION,
+  EXPR_ARRAY_SECTION,
   EXPR_OMP_ARRAY_SHAPING,
   EXPR_OMP_ITERATOR,
 
@@ -2132,7 +1983,7 @@ enum CleanupObjectKind { COK_Block, COK_CompoundLiteral };
 /// Describes the categories of an Objective-C class.
 struct ObjCCategoriesInfo {
   // The ID of the definition
-  DeclID DefinitionID;
+  LocalDeclID DefinitionID;
 
   // Offset into the array of category lists.
   unsigned Offset;
@@ -2231,27 +2082,6 @@ template <> struct DenseMapInfo<clang::serialization::DeclarationNameKey> {
   }
 };
 
-template <> struct DenseMapInfo<clang::serialization::GlobalDeclID> {
-  using DeclID = clang::serialization::DeclID;
-  using GlobalDeclID = clang::serialization::GlobalDeclID;
-
-  static GlobalDeclID getEmptyKey() {
-    return GlobalDeclID(DenseMapInfo<DeclID>::getEmptyKey());
-  }
-
-  static GlobalDeclID getTombstoneKey() {
-    return GlobalDeclID(DenseMapInfo<DeclID>::getTombstoneKey());
-  }
-
-  static unsigned getHashValue(const GlobalDeclID &Key) {
-    return DenseMapInfo<DeclID>::getHashValue(Key.get());
-  }
-
-  static bool isEqual(const GlobalDeclID &L, const GlobalDeclID &R) {
-    return L == R;
-  }
-};
-
 } // namespace llvm
 
 #endif // LLVM_CLANG_SERIALIZATION_ASTBITCODES_H
diff --git a/clang/include/clang/Serialization/ASTDeserializationListener.h b/clang/include/clang/Serialization/ASTDeserializationListener.h
@@ -44,7 +44,7 @@ class ASTDeserializationListener {
   ///        unqualified.
   virtual void TypeRead(serialization::TypeIdx Idx, QualType T) { }
   /// A decl was deserialized from the AST file.
-  virtual void DeclRead(serialization::DeclID ID, const Decl *D) { }
+  virtual void DeclRead(GlobalDeclID ID, const Decl *D) {}
   /// A selector was read from the AST file.
   virtual void SelectorRead(serialization::SelectorID iD, Selector Sel) {}
   /// A macro definition was read from the AST file.

diff --git a/clang/include/clang/Serialization/ASTReader.h b/clang/include/clang/Serialization/ASTReader.h
@@ -501,27 +501,23 @@ class ASTReader
   /// = I + 1 has already been loaded.
   llvm::PagedVector<Decl *> DeclsLoaded;
 
-  static_assert(std::is_same_v<serialization::DeclID, Decl::DeclID>);
-
-  using GlobalDeclMapType =
-      ContinuousRangeMap<serialization::GlobalDeclID, ModuleFile *, 4>;
+  using GlobalDeclMapType = ContinuousRangeMap<GlobalDeclID, ModuleFile *, 4>;
 
   /// Mapping from global declaration IDs to the module in which the
   /// declaration resides.
   GlobalDeclMapType GlobalDeclMap;
 
   using FileOffset = std::pair<ModuleFile *, uint64_t>;
   using FileOffsetsTy = SmallVector<FileOffset, 2>;
-  using DeclUpdateOffsetsMap =
-      llvm::DenseMap<serialization::GlobalDeclID, FileOffsetsTy>;
+  using DeclUpdateOffsetsMap = llvm::DenseMap<GlobalDeclID, FileOffsetsTy>;
 
   /// Declarations that have modifications residing in a later file
   /// in the chain.
   DeclUpdateOffsetsMap DeclUpdateOffsets;
 
-  using DelayedNamespaceOffsetMapTy = llvm::DenseMap<
-      serialization::GlobalDeclID,
-      std::pair</*LexicalOffset*/ uint64_t, /*VisibleOffset*/ uint64_t>>;
+  using DelayedNamespaceOffsetMapTy =
+      llvm::DenseMap<GlobalDeclID, std::pair</*LexicalOffset*/ uint64_t,
+                                             /*VisibleOffset*/ uint64_t>>;
 
   /// Mapping from global declaration IDs to the lexical and visible block
   /// offset for delayed namespace in reduced BMI.
@@ -535,13 +531,12 @@ class ASTReader
 
   struct PendingUpdateRecord {
     Decl *D;
-    serialization::GlobalDeclID ID;
+    GlobalDeclID ID;
 
     // Whether the declaration was just deserialized.
     bool JustLoaded;
 
-    PendingUpdateRecord(serialization::GlobalDeclID ID, Decl *D,
-                        bool JustLoaded)
+    PendingUpdateRecord(GlobalDeclID ID, Decl *D, bool JustLoaded)
         : D(D), ID(ID), JustLoaded(JustLoaded) {}
   };
 
@@ -594,10 +589,10 @@ class ASTReader
 
   struct FileDeclsInfo {
     ModuleFile *Mod = nullptr;
-    ArrayRef<serialization::LocalDeclID> Decls;
+    ArrayRef<LocalDeclID> Decls;
 
     FileDeclsInfo() = default;
-    FileDeclsInfo(ModuleFile *Mod, ArrayRef<serialization::LocalDeclID> Decls)
+    FileDeclsInfo(ModuleFile *Mod, ArrayRef<LocalDeclID> Decls)
         : Mod(Mod), Decls(Decls) {}
   };
 
@@ -635,8 +630,7 @@ class ASTReader
 
   /// Updates to the visible declarations of declaration contexts that
   /// haven't been loaded yet.
-  llvm::DenseMap<serialization::GlobalDeclID, DeclContextVisibleUpdates>
-      PendingVisibleUpdates;
+  llvm::DenseMap<GlobalDeclID, DeclContextVisibleUpdates> PendingVisibleUpdates;
 
   /// The set of C++ or Objective-C classes that have forward
   /// declarations that have not yet been linked to their definitions.
@@ -662,8 +656,7 @@ class ASTReader
   /// Read the record that describes the visible contents of a DC.
   bool ReadVisibleDeclContextStorage(ModuleFile &M,
                                      llvm::BitstreamCursor &Cursor,
-                                     uint64_t Offset,
-                                     serialization::GlobalDeclID ID);
+                                     uint64_t Offset, GlobalDeclID ID);
 
   /// A vector containing identifiers that have already been
   /// loaded.
@@ -816,22 +809,22 @@ class ASTReader
   /// This contains the data loaded from all EAGERLY_DESERIALIZED_DECLS blocks
   /// in the chain. The referenced declarations are deserialized and passed to
   /// the consumer eagerly.
-  SmallVector<serialization::GlobalDeclID, 16> EagerlyDeserializedDecls;
+  SmallVector<GlobalDeclID, 16> EagerlyDeserializedDecls;
 
   /// The IDs of all tentative definitions stored in the chain.
   ///
   /// Sema keeps track of all tentative definitions in a TU because it has to
   /// complete them and pass them on to CodeGen. Thus, tentative definitions in
   /// the PCH chain must be eagerly deserialized.
-  SmallVector<serialization::GlobalDeclID, 16> TentativeDefinitions;
+  SmallVector<GlobalDeclID, 16> TentativeDefinitions;
 
   /// The IDs of all CXXRecordDecls stored in the chain whose VTables are
   /// used.
   ///
   /// CodeGen has to emit VTables for these records, so they have to be eagerly
   /// deserialized.
   struct VTableUse {
-    serialization::GlobalDeclID ID;
+    GlobalDeclID ID;
     SourceLocation::UIntTy RawLoc;
     bool Used;
   };
@@ -844,7 +837,7 @@ class ASTReader
   /// instantiation where the first value is the ID of the decl and the second
   /// is the instantiation location.
   struct PendingInstantiation {
-    serialization::GlobalDeclID ID;
+    GlobalDeclID ID;
     SourceLocation::UIntTy RawLoc;
   };
   SmallVector<PendingInstantiation, 64> PendingInstantiations;
@@ -857,11 +850,11 @@ class ASTReader
 
   /// A snapshot of Sema's unused file-scoped variable tracking, for
   /// generating warnings.
-  SmallVector<serialization::GlobalDeclID, 16> UnusedFileScopedDecls;
+  SmallVector<GlobalDeclID, 16> UnusedFileScopedDecls;
 
   /// A list of all the delegating constructors we've seen, to diagnose
   /// cycles.
-  SmallVector<serialization::GlobalDeclID, 4> DelegatingCtorDecls;
+  SmallVector<GlobalDeclID, 4> DelegatingCtorDecls;
 
   /// Method selectors used in a @selector expression. Used for
   /// implementation of -Wselector.
@@ -874,7 +867,7 @@ class ASTReader
   /// The IDs of type aliases for ext_vectors that exist in the chain.
   ///
   /// Used by Sema for finding sugared names for ext_vectors in diagnostics.
-  SmallVector<serialization::GlobalDeclID, 4> ExtVectorDecls;
+  SmallVector<GlobalDeclID, 4> ExtVectorDecls;
 
   //@}
 
@@ -885,7 +878,7 @@ class ASTReader
   /// The IDs of all potentially unused typedef names in the chain.
   ///
   /// Sema tracks these to emit warnings.
-  SmallVector<serialization::GlobalDeclID, 16> UnusedLocalTypedefNameCandidates;
+  SmallVector<GlobalDeclID, 16> UnusedLocalTypedefNameCandidates;
 
   /// Our current depth in #pragma cuda force_host_device begin/end
   /// macros.
@@ -894,7 +887,7 @@ class ASTReader
   /// The IDs of the declarations Sema stores directly.
   ///
   /// Sema tracks a few important decls, such as namespace std, directly.
-  SmallVector<serialization::GlobalDeclID, 4> SemaDeclRefs;
+  SmallVector<GlobalDeclID, 4> SemaDeclRefs;
 
   /// The IDs of the types ASTContext stores directly.
   ///
@@ -905,7 +898,7 @@ class ASTReader
   ///
   /// The AST context tracks a few important decls, currently cudaConfigureCall,
   /// directly.
-  SmallVector<serialization::GlobalDeclID, 2> CUDASpecialDeclRefs;
+  SmallVector<GlobalDeclID, 2> CUDASpecialDeclRefs;
 
   /// The floating point pragma option settings.
   SmallVector<uint64_t, 1> FPPragmaOptions;
@@ -954,12 +947,12 @@ class ASTReader
   llvm::DenseMap<const Decl *, std::set<std::string>> OpenCLDeclExtMap;
 
   /// A list of the namespaces we've seen.
-  SmallVector<serialization::GlobalDeclID, 4> KnownNamespaces;
+  SmallVector<GlobalDeclID, 4> KnownNamespaces;
 
   /// A list of undefined decls with internal linkage followed by the
   /// SourceLocation of a matching ODR-use.
   struct UndefinedButUsedDecl {
-    serialization::GlobalDeclID ID;
+    GlobalDeclID ID;
     SourceLocation::UIntTy RawLoc;
   };
   SmallVector<UndefinedButUsedDecl, 8> UndefinedButUsed;
@@ -974,8 +967,7 @@ class ASTReader
   /// The IDs of all decls to be checked for deferred diags.
   ///
   /// Sema tracks these to emit deferred diags.
-  llvm::SmallSetVector<serialization::GlobalDeclID, 4>
-      DeclsToCheckForDeferredDiags;
+  llvm::SmallSetVector<GlobalDeclID, 4> DeclsToCheckForDeferredDiags;
 
 private:
   struct ImportedSubmodule {
@@ -1112,7 +1104,7 @@ class ASTReader
   ///
   /// The declarations on the identifier chain for these identifiers will be
   /// loaded once the recursive loading has completed.
-  llvm::MapVector<IdentifierInfo *, SmallVector<serialization::GlobalDeclID, 4>>
+  llvm::MapVector<IdentifierInfo *, SmallVector<GlobalDeclID, 4>>
       PendingIdentifierInfos;
 
   /// The set of lookup results that we have faked in order to support
@@ -1157,8 +1149,8 @@ class ASTReader
   /// been loaded but its DeclContext was not set yet.
   struct PendingDeclContextInfo {
     Decl *D;
-    serialization::GlobalDeclID SemaDC;
-    serialization::GlobalDeclID LexicalDC;
+    GlobalDeclID SemaDC;
+    GlobalDeclID LexicalDC;
   };
 
   /// The set of Decls that have been loaded but their DeclContexts are
@@ -1239,8 +1231,7 @@ class ASTReader
   /// module is loaded.
   SmallVector<ObjCInterfaceDecl *, 16> ObjCClassesLoaded;
 
-  using KeyDeclsMap =
-      llvm::DenseMap<Decl *, SmallVector<serialization::GlobalDeclID, 2>>;
+  using KeyDeclsMap = llvm::DenseMap<Decl *, SmallVector<GlobalDeclID, 2>>;
 
   /// A mapping from canonical declarations to the set of global
   /// declaration IDs for key declaration that have been merged with that
@@ -1449,19 +1440,18 @@ class ASTReader
   QualType readTypeRecord(unsigned Index);
   RecordLocation TypeCursorForIndex(unsigned Index);
   void LoadedDecl(unsigned Index, Decl *D);
-  Decl *ReadDeclRecord(serialization::GlobalDeclID ID);
+  Decl *ReadDeclRecord(GlobalDeclID ID);
   void markIncompleteDeclChain(Decl *D);
 
   /// Returns the most recent declaration of a declaration (which must be
   /// of a redeclarable kind) that is either local or has already been loaded
   /// merged into its redecl chain.
   Decl *getMostRecentExistingDecl(Decl *D);
 
-  RecordLocation DeclCursorForID(serialization::GlobalDeclID ID,
-                                 SourceLocation &Location);
+  RecordLocation DeclCursorForID(GlobalDeclID ID, SourceLocation &Location);
   void loadDeclUpdateRecords(PendingUpdateRecord &Record);
   void loadPendingDeclChain(Decl *D, uint64_t LocalOffset);
-  void loadObjCCategories(serialization::GlobalDeclID ID, ObjCInterfaceDecl *D,
+  void loadObjCCategories(GlobalDeclID ID, ObjCInterfaceDecl *D,
                           unsigned PreviousGeneration = 0);
 
   RecordLocation getLocalBitOffset(uint64_t GlobalOffset);
@@ -1496,19 +1486,18 @@ class ASTReader
                                unsigned ClientLoadCapabilities);
 
 public:
-  class ModuleDeclIterator
-      : public llvm::iterator_adaptor_base<
-            ModuleDeclIterator, const serialization::LocalDeclID *,
-            std::random_access_iterator_tag, const Decl *, ptrdiff_t,
-            const Decl *, const Decl *> {
+  class ModuleDeclIterator : public llvm::iterator_adaptor_base<
+                                 ModuleDeclIterator, const LocalDeclID *,
+                                 std::random_access_iterator_tag, const Decl *,
+                                 ptrdiff_t, const Decl *, const Decl *> {
     ASTReader *Reader = nullptr;
     ModuleFile *Mod = nullptr;
 
   public:
     ModuleDeclIterator() : iterator_adaptor_base(nullptr) {}
 
     ModuleDeclIterator(ASTReader *Reader, ModuleFile *Mod,
-                       const serialization::LocalDeclID *Pos)
+                       const LocalDeclID *Pos)
         : iterator_adaptor_base(Pos), Reader(Reader), Mod(Mod) {}
 
     value_type operator*() const {
@@ -1536,9 +1525,8 @@ class ASTReader
 
   void pushExternalDeclIntoScope(NamedDecl *D, DeclarationName Name);
 
-  void addPendingDeclContextInfo(Decl *D,
-                                 serialization::GlobalDeclID SemaDC,
-                                 serialization::GlobalDeclID LexicalDC) {
+  void addPendingDeclContextInfo(Decl *D, GlobalDeclID SemaDC,
+                                 GlobalDeclID LexicalDC) {
     assert(D);
     PendingDeclContextInfo Info = { D, SemaDC, LexicalDC };
     PendingDeclContextInfos.push_back(Info);
@@ -1916,38 +1904,36 @@ class ASTReader
 
   /// Map from a local declaration ID within a given module to a
   /// global declaration ID.
-  serialization::GlobalDeclID
-  getGlobalDeclID(ModuleFile &F, serialization::LocalDeclID LocalID) const;
+  GlobalDeclID getGlobalDeclID(ModuleFile &F, LocalDeclID LocalID) const;
 
   /// Returns true if global DeclID \p ID originated from module \p M.
-  bool isDeclIDFromModule(serialization::GlobalDeclID ID, ModuleFile &M) const;
+  bool isDeclIDFromModule(GlobalDeclID ID, ModuleFile &M) const;
 
   /// Retrieve the module file that owns the given declaration, or NULL
   /// if the declaration is not from a module file.
   ModuleFile *getOwningModuleFile(const Decl *D);
 
   /// Returns the source location for the decl \p ID.
-  SourceLocation getSourceLocationForDeclID(serialization::GlobalDeclID ID);
+  SourceLocation getSourceLocationForDeclID(GlobalDeclID ID);
 
   /// Resolve a declaration ID into a declaration, potentially
   /// building a new declaration.
-  Decl *GetDecl(serialization::GlobalDeclID ID);
-  Decl *GetExternalDecl(Decl::DeclID ID) override;
+  Decl *GetDecl(GlobalDeclID ID);
+  Decl *GetExternalDecl(GlobalDeclID ID) override;
 
   /// Resolve a declaration ID into a declaration. Return 0 if it's not
   /// been loaded yet.
-  Decl *GetExistingDecl(serialization::GlobalDeclID ID);
+  Decl *GetExistingDecl(GlobalDeclID ID);
 
   /// Reads a declaration with the given local ID in the given module.
-  Decl *GetLocalDecl(ModuleFile &F, serialization::LocalDeclID LocalID) {
+  Decl *GetLocalDecl(ModuleFile &F, LocalDeclID LocalID) {
     return GetDecl(getGlobalDeclID(F, LocalID));
   }
 
   /// Reads a declaration with the given local ID in the given module.
   ///
   /// \returns The requested declaration, casted to the given return type.
-  template <typename T>
-  T *GetLocalDeclAs(ModuleFile &F, serialization::LocalDeclID LocalID) {
+  template <typename T> T *GetLocalDeclAs(ModuleFile &F, LocalDeclID LocalID) {
     return cast_or_null<T>(GetLocalDecl(F, LocalID));
   }
 
@@ -1956,16 +1942,15 @@ class ASTReader
   ///
   /// \returns the global ID of the given declaration as known in the given
   /// module file.
-  serialization::DeclID
-  mapGlobalIDToModuleFileGlobalID(ModuleFile &M,
-                                  serialization::GlobalDeclID GlobalID);
+  LocalDeclID mapGlobalIDToModuleFileGlobalID(ModuleFile &M,
+                                              GlobalDeclID GlobalID);
 
   /// Reads a declaration ID from the given position in a record in the
   /// given module.
   ///
   /// \returns The declaration ID read from the record, adjusted to a global ID.
-  serialization::GlobalDeclID
-  ReadDeclID(ModuleFile &F, const RecordData &Record, unsigned &Idx);
+  GlobalDeclID ReadDeclID(ModuleFile &F, const RecordData &Record,
+                          unsigned &Idx);
 
   /// Reads a declaration from the given position in a record in the
   /// given module.
@@ -2139,10 +2124,9 @@ class ASTReader
   void LoadSelector(Selector Sel);
 
   void SetIdentifierInfo(unsigned ID, IdentifierInfo *II);
-  void SetGloballyVisibleDecls(
-      IdentifierInfo *II,
-      const SmallVectorImpl<serialization::GlobalDeclID> &DeclIDs,
-      SmallVectorImpl<Decl *> *Decls = nullptr);
+  void SetGloballyVisibleDecls(IdentifierInfo *II,
+                               const SmallVectorImpl<GlobalDeclID> &DeclIDs,
+                               SmallVectorImpl<Decl *> *Decls = nullptr);
 
   /// Report a diagnostic.
   DiagnosticBuilder Diag(unsigned DiagID) const;
@@ -2383,7 +2367,7 @@ class ASTReader
 
   // Contains the IDs for declarations that were requested before we have
   // access to a Sema object.
-  SmallVector<serialization::GlobalDeclID, 16> PreloadedDeclIDs;
+  SmallVector<GlobalDeclID, 16> PreloadedDeclIDs;
 
   /// Retrieve the semantic analysis object used to analyze the
   /// translation unit in which the precompiled header is being

diff --git a/clang/include/clang/Serialization/ASTRecordReader.h b/clang/include/clang/Serialization/ASTRecordReader.h
@@ -136,7 +136,7 @@ class ASTRecordReader
   /// Reads a declaration with the given local ID in the given module.
   ///
   /// \returns The requested declaration, casted to the given return type.
-  template <typename T> T *GetLocalDeclAs(serialization::LocalDeclID LocalID) {
+  template <typename T> T *GetLocalDeclAs(LocalDeclID LocalID) {
     return cast_or_null<T>(Reader->GetLocalDecl(*F, LocalID));
   }
 
@@ -182,9 +182,7 @@ class ASTRecordReader
   /// Reads a declaration ID from the given position in this record.
   ///
   /// \returns The declaration ID read from the record, adjusted to a global ID.
-  serialization::GlobalDeclID readDeclID() {
-    return Reader->ReadDeclID(*F, Record, Idx);
-  }
+  GlobalDeclID readDeclID() { return Reader->ReadDeclID(*F, Record, Idx); }
 
   /// Reads a declaration from the given position in a record in the
   /// given module, advancing Idx.

diff --git a/clang/include/clang/Serialization/ASTWriter.h b/clang/include/clang/Serialization/ASTWriter.h
@@ -212,18 +212,18 @@ class ASTWriter : public ASTDeserializationListener,
   llvm::SmallVector<NamespaceDecl *, 16> DelayedNamespace;
 
   /// The first ID number we can use for our own declarations.
-  serialization::DeclID FirstDeclID = serialization::NUM_PREDEF_DECL_IDS;
+  LocalDeclID FirstDeclID = LocalDeclID(clang::NUM_PREDEF_DECL_IDS);
 
   /// The decl ID that will be assigned to the next new decl.
-  serialization::DeclID NextDeclID = FirstDeclID;
+  LocalDeclID NextDeclID = FirstDeclID;
 
   /// Map that provides the ID numbers of each declaration within
   /// the output stream, as well as those deserialized from a chained PCH.
   ///
   /// The ID numbers of declarations are consecutive (in order of
   /// discovery) and start at 2. 1 is reserved for the translation
   /// unit, while 0 is reserved for NULL.
-  llvm::DenseMap<const Decl *, serialization::DeclID> DeclIDs;
+  llvm::DenseMap<const Decl *, LocalDeclID> DeclIDs;
 
   /// Offset of each declaration in the bitstream, indexed by
   /// the declaration's ID.
@@ -233,9 +233,8 @@ class ASTWriter : public ASTDeserializationListener,
   /// are relative to this value.
   uint64_t DeclTypesBlockStartOffset = 0;
 
-  /// Sorted (by file offset) vector of pairs of file offset/DeclID.
-  using LocDeclIDsTy =
-      SmallVector<std::pair<unsigned, serialization::DeclID>, 64>;
+  /// Sorted (by file offset) vector of pairs of file offset/LocalDeclID.
+  using LocDeclIDsTy = SmallVector<std::pair<unsigned, LocalDeclID>, 64>;
   struct DeclIDInFileInfo {
     LocDeclIDsTy DeclIDs;
 
@@ -250,7 +249,7 @@ class ASTWriter : public ASTDeserializationListener,
   /// that it contains.
   FileDeclIDsTy FileDeclIDs;
 
-  void associateDeclWithFile(const Decl *D, serialization::DeclID);
+  void associateDeclWithFile(const Decl *D, LocalDeclID);
 
   /// The first ID number we can use for our own types.
   serialization::TypeID FirstTypeID = serialization::NUM_PREDEF_TYPE_IDS;
@@ -421,8 +420,8 @@ class ASTWriter : public ASTDeserializationListener,
   /// headers. The declarations themselves are stored as declaration
   /// IDs, since they will be written out to an EAGERLY_DESERIALIZED_DECLS
   /// record.
-  SmallVector<serialization::DeclID, 16> EagerlyDeserializedDecls;
-  SmallVector<serialization::DeclID, 16> ModularCodegenDecls;
+  RecordData EagerlyDeserializedDecls;
+  RecordData ModularCodegenDecls;
 
   /// DeclContexts that have received extensions since their serialized
   /// form.
@@ -709,20 +708,21 @@ class ASTWriter : public ASTDeserializationListener,
       return false;
     auto I = DeclIDs.find(D);
     return (I == DeclIDs.end() ||
-            I->second >= serialization::NUM_PREDEF_DECL_IDS);
+            I->second.get() >= clang::NUM_PREDEF_DECL_IDS);
   };
 
   /// Emit a reference to a declaration.
   void AddDeclRef(const Decl *D, RecordDataImpl &Record);
   // Emit a reference to a declaration if the declaration was emitted.
   void AddEmittedDeclRef(const Decl *D, RecordDataImpl &Record);
 
-  /// Force a declaration to be emitted and get its ID.
-  serialization::DeclID GetDeclRef(const Decl *D);
+  /// Force a declaration to be emitted and get its local ID to the module file
+  /// been writing.
+  LocalDeclID GetDeclRef(const Decl *D);
 
-  /// Determine the declaration ID of an already-emitted
+  /// Determine the local declaration ID of an already-emitted
   /// declaration.
-  serialization::DeclID getDeclID(const Decl *D);
+  LocalDeclID getDeclID(const Decl *D);
 
   /// Whether or not the declaration got emitted. If not, it wouldn't be
   /// emitted.

diff --git a/clang/include/clang/Serialization/ModuleFile.h b/clang/include/clang/Serialization/ModuleFile.h
@@ -474,7 +474,7 @@ class ModuleFile {
   llvm::DenseMap<ModuleFile *, serialization::DeclID> GlobalToLocalDeclIDs;
 
   /// Array of file-level DeclIDs sorted by file.
-  const serialization::LocalDeclID *FileSortedDecls = nullptr;
+  const LocalDeclID *FileSortedDecls = nullptr;
   unsigned NumFileSortedDecls = 0;
 
   /// Array of category list location information within this

diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
@@ -1084,7 +1084,7 @@ void ASTContext::addModuleInitializer(Module *M, Decl *D) {
 }
 
 void ASTContext::addLazyModuleInitializers(Module *M,
-                                           ArrayRef<Decl::DeclID> IDs) {
+                                           ArrayRef<GlobalDeclID> IDs) {
   auto *&Inits = ModuleInitializers[M];
   if (!Inits)
     Inits = new (*this) PerModuleInitializers;
@@ -1321,16 +1321,14 @@ void ASTContext::InitBuiltinTypes(const TargetInfo &Target,
 
   // Placeholder type for OMP array sections.
   if (LangOpts.OpenMP) {
-    InitBuiltinType(OMPArraySectionTy, BuiltinType::OMPArraySection);
+    InitBuiltinType(ArraySectionTy, BuiltinType::ArraySection);
     InitBuiltinType(OMPArrayShapingTy, BuiltinType::OMPArrayShaping);
     InitBuiltinType(OMPIteratorTy, BuiltinType::OMPIterator);
   }
-  // Placeholder type for OpenACC array sections.
-  if (LangOpts.OpenACC) {
-    // FIXME: Once we implement OpenACC array sections in Sema, this will either
-    // be combined with the OpenMP type, or given its own type. In the meantime,
-    // just use the OpenMP type so that parsing can work.
-    InitBuiltinType(OMPArraySectionTy, BuiltinType::OMPArraySection);
+  // Placeholder type for OpenACC array sections, if we are ALSO in OMP mode,
+  // don't bother, as we're just using the same type as OMP.
+  if (LangOpts.OpenACC && !LangOpts.OpenMP) {
+    InitBuiltinType(ArraySectionTy, BuiltinType::ArraySection);
   }
   if (LangOpts.MatrixTypes)
     InitBuiltinType(IncompleteMatrixIdxTy, BuiltinType::IncompleteMatrixIdx);

diff --git a/clang/lib/AST/ComputeDependence.cpp b/clang/lib/AST/ComputeDependence.cpp
@@ -443,12 +443,17 @@ ExprDependence clang::computeDependence(ObjCIndirectCopyRestoreExpr *E) {
   return E->getSubExpr()->getDependence();
 }
 
-ExprDependence clang::computeDependence(OMPArraySectionExpr *E) {
+ExprDependence clang::computeDependence(ArraySectionExpr *E) {
   auto D = E->getBase()->getDependence();
   if (auto *LB = E->getLowerBound())
     D |= LB->getDependence();
   if (auto *Len = E->getLength())
     D |= Len->getDependence();
+
+  if (E->isOMPArraySection()) {
+    if (auto *Stride = E->getStride())
+      D |= Stride->getDependence();
+  }
   return D;
 }
 

diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
@@ -2151,7 +2151,7 @@ VarDecl *VarDecl::Create(ASTContext &C, DeclContext *DC, SourceLocation StartL,
   return new (C, DC) VarDecl(Var, C, DC, StartL, IdL, Id, T, TInfo, S);
 }
 
-VarDecl *VarDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+VarDecl *VarDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   return new (C, ID)
       VarDecl(Var, C, nullptr, SourceLocation(), SourceLocation(), nullptr,
               QualType(), nullptr, SC_None);
@@ -2929,7 +2929,7 @@ QualType ParmVarDecl::getOriginalType() const {
   return T;
 }
 
-ParmVarDecl *ParmVarDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+ParmVarDecl *ParmVarDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   return new (C, ID)
       ParmVarDecl(ParmVar, C, nullptr, SourceLocation(), SourceLocation(),
                   nullptr, QualType(), nullptr, SC_None, nullptr);
@@ -4553,7 +4553,7 @@ FieldDecl *FieldDecl::Create(const ASTContext &C, DeclContext *DC,
                                BW, Mutable, InitStyle);
 }
 
-FieldDecl *FieldDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+FieldDecl *FieldDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   return new (C, ID) FieldDecl(Field, nullptr, SourceLocation(),
                                SourceLocation(), nullptr, QualType(), nullptr,
                                nullptr, false, ICIS_NoInit);
@@ -4863,7 +4863,7 @@ EnumDecl *EnumDecl::Create(ASTContext &C, DeclContext *DC,
   return Enum;
 }
 
-EnumDecl *EnumDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+EnumDecl *EnumDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   EnumDecl *Enum =
       new (C, ID) EnumDecl(C, nullptr, SourceLocation(), SourceLocation(),
                            nullptr, nullptr, false, false, false);
@@ -5025,7 +5025,8 @@ RecordDecl *RecordDecl::Create(const ASTContext &C, TagKind TK, DeclContext *DC,
   return R;
 }
 
-RecordDecl *RecordDecl::CreateDeserialized(const ASTContext &C, Decl::DeclID ID) {
+RecordDecl *RecordDecl::CreateDeserialized(const ASTContext &C,
+                                           GlobalDeclID ID) {
   RecordDecl *R = new (C, ID)
       RecordDecl(Record, TagTypeKind::Struct, C, nullptr, SourceLocation(),
                  SourceLocation(), nullptr, nullptr);
@@ -5297,7 +5298,7 @@ PragmaCommentDecl *PragmaCommentDecl::Create(const ASTContext &C,
 }
 
 PragmaCommentDecl *PragmaCommentDecl::CreateDeserialized(ASTContext &C,
-                                                         Decl::DeclID ID,
+                                                         GlobalDeclID ID,
                                                          unsigned ArgSize) {
   return new (C, ID, additionalSizeToAlloc<char>(ArgSize + 1))
       PragmaCommentDecl(nullptr, SourceLocation(), PCK_Unknown);
@@ -5322,7 +5323,7 @@ PragmaDetectMismatchDecl::Create(const ASTContext &C, TranslationUnitDecl *DC,
 }
 
 PragmaDetectMismatchDecl *
-PragmaDetectMismatchDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID,
+PragmaDetectMismatchDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID,
                                              unsigned NameValueSize) {
   return new (C, ID, additionalSizeToAlloc<char>(NameValueSize + 1))
       PragmaDetectMismatchDecl(nullptr, SourceLocation(), 0);
@@ -5349,7 +5350,7 @@ LabelDecl *LabelDecl::Create(ASTContext &C, DeclContext *DC,
   return new (C, DC) LabelDecl(DC, IdentL, II, nullptr, GnuLabelL);
 }
 
-LabelDecl *LabelDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+LabelDecl *LabelDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   return new (C, ID) LabelDecl(nullptr, SourceLocation(), nullptr, nullptr,
                                SourceLocation());
 }
@@ -5390,7 +5391,7 @@ ImplicitParamDecl *ImplicitParamDecl::Create(ASTContext &C, QualType Type,
 }
 
 ImplicitParamDecl *ImplicitParamDecl::CreateDeserialized(ASTContext &C,
-                                                         Decl::DeclID ID) {
+                                                         GlobalDeclID ID) {
   return new (C, ID) ImplicitParamDecl(C, QualType(), ImplicitParamKind::Other);
 }
 
@@ -5408,7 +5409,7 @@ FunctionDecl::Create(ASTContext &C, DeclContext *DC, SourceLocation StartLoc,
   return New;
 }
 
-FunctionDecl *FunctionDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+FunctionDecl *FunctionDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   return new (C, ID) FunctionDecl(
       Function, C, nullptr, SourceLocation(), DeclarationNameInfo(), QualType(),
       nullptr, SC_None, false, false, ConstexprSpecKind::Unspecified, nullptr);
@@ -5418,7 +5419,7 @@ BlockDecl *BlockDecl::Create(ASTContext &C, DeclContext *DC, SourceLocation L) {
   return new (C, DC) BlockDecl(DC, L);
 }
 
-BlockDecl *BlockDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+BlockDecl *BlockDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   return new (C, ID) BlockDecl(nullptr, SourceLocation());
 }
 
@@ -5432,7 +5433,7 @@ CapturedDecl *CapturedDecl::Create(ASTContext &C, DeclContext *DC,
       CapturedDecl(DC, NumParams);
 }
 
-CapturedDecl *CapturedDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID,
+CapturedDecl *CapturedDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID,
                                                unsigned NumParams) {
   return new (C, ID, additionalSizeToAlloc<ImplicitParamDecl *>(NumParams))
       CapturedDecl(nullptr, NumParams);
@@ -5458,8 +5459,8 @@ EnumConstantDecl *EnumConstantDecl::Create(ASTContext &C, EnumDecl *CD,
   return new (C, CD) EnumConstantDecl(C, CD, L, Id, T, E, V);
 }
 
-EnumConstantDecl *
-EnumConstantDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+EnumConstantDecl *EnumConstantDecl::CreateDeserialized(ASTContext &C,
+                                                       GlobalDeclID ID) {
   return new (C, ID) EnumConstantDecl(C, nullptr, SourceLocation(), nullptr,
                                       QualType(), nullptr, llvm::APSInt());
 }
@@ -5486,7 +5487,7 @@ IndirectFieldDecl::Create(ASTContext &C, DeclContext *DC, SourceLocation L,
 }
 
 IndirectFieldDecl *IndirectFieldDecl::CreateDeserialized(ASTContext &C,
-                                                         Decl::DeclID ID) {
+                                                         GlobalDeclID ID) {
   return new (C, ID)
       IndirectFieldDecl(C, nullptr, SourceLocation(), DeclarationName(),
                         QualType(), std::nullopt);
@@ -5547,7 +5548,7 @@ bool TypedefNameDecl::isTransparentTagSlow() const {
   return isTransparent;
 }
 
-TypedefDecl *TypedefDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+TypedefDecl *TypedefDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   return new (C, ID) TypedefDecl(C, nullptr, SourceLocation(), SourceLocation(),
                                  nullptr, nullptr);
 }
@@ -5560,7 +5561,8 @@ TypeAliasDecl *TypeAliasDecl::Create(ASTContext &C, DeclContext *DC,
   return new (C, DC) TypeAliasDecl(C, DC, StartLoc, IdLoc, Id, TInfo);
 }
 
-TypeAliasDecl *TypeAliasDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+TypeAliasDecl *TypeAliasDecl::CreateDeserialized(ASTContext &C,
+                                                 GlobalDeclID ID) {
   return new (C, ID) TypeAliasDecl(C, nullptr, SourceLocation(),
                                    SourceLocation(), nullptr, nullptr);
 }
@@ -5591,7 +5593,7 @@ FileScopeAsmDecl *FileScopeAsmDecl::Create(ASTContext &C, DeclContext *DC,
 }
 
 FileScopeAsmDecl *FileScopeAsmDecl::CreateDeserialized(ASTContext &C,
-                                                       Decl::DeclID ID) {
+                                                       GlobalDeclID ID) {
   return new (C, ID) FileScopeAsmDecl(nullptr, nullptr, SourceLocation(),
                                       SourceLocation());
 }
@@ -5609,7 +5611,7 @@ TopLevelStmtDecl *TopLevelStmtDecl::Create(ASTContext &C, Stmt *Statement) {
 }
 
 TopLevelStmtDecl *TopLevelStmtDecl::CreateDeserialized(ASTContext &C,
-                                                       Decl::DeclID ID) {
+                                                       GlobalDeclID ID) {
   return new (C, ID)
       TopLevelStmtDecl(/*DC=*/nullptr, SourceLocation(), /*S=*/nullptr);
 }
@@ -5630,7 +5632,7 @@ EmptyDecl *EmptyDecl::Create(ASTContext &C, DeclContext *DC, SourceLocation L) {
   return new (C, DC) EmptyDecl(DC, L);
 }
 
-EmptyDecl *EmptyDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+EmptyDecl *EmptyDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   return new (C, ID) EmptyDecl(nullptr, SourceLocation());
 }
 
@@ -5663,7 +5665,8 @@ HLSLBufferDecl *HLSLBufferDecl::Create(ASTContext &C,
   return Result;
 }
 
-HLSLBufferDecl *HLSLBufferDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+HLSLBufferDecl *HLSLBufferDecl::CreateDeserialized(ASTContext &C,
+                                                   GlobalDeclID ID) {
   return new (C, ID) HLSLBufferDecl(nullptr, false, SourceLocation(), nullptr,
                                     SourceLocation(), SourceLocation());
 }
@@ -5719,7 +5722,7 @@ ImportDecl *ImportDecl::CreateImplicit(ASTContext &C, DeclContext *DC,
   return Import;
 }
 
-ImportDecl *ImportDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID,
+ImportDecl *ImportDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID,
                                            unsigned NumLocations) {
   return new (C, ID, additionalSizeToAlloc<SourceLocation>(NumLocations))
       ImportDecl(EmptyShell());
@@ -5752,6 +5755,6 @@ ExportDecl *ExportDecl::Create(ASTContext &C, DeclContext *DC,
   return new (C, DC) ExportDecl(DC, ExportLoc);
 }
 
-ExportDecl *ExportDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+ExportDecl *ExportDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   return new (C, ID) ExportDecl(nullptr, SourceLocation());
 }
diff --git a/clang/lib/AST/DeclBase.cpp b/clang/lib/AST/DeclBase.cpp
@@ -71,7 +71,7 @@ void Decl::updateOutOfDate(IdentifierInfo &II) const {
 #include "clang/AST/DeclNodes.inc"
 
 void *Decl::operator new(std::size_t Size, const ASTContext &Context,
-                         Decl::DeclID ID, std::size_t Extra) {
+                         GlobalDeclID ID, std::size_t Extra) {
   // Allocate an extra 8 bytes worth of storage, which ensures that the
   // resulting pointer will still be 8-byte aligned.
   static_assert(sizeof(unsigned) * 2 >= alignof(Decl),
@@ -85,7 +85,7 @@ void *Decl::operator new(std::size_t Size, const ASTContext &Context,
   PrefixPtr[0] = 0;
 
   // Store the global declaration ID in the second 4 bytes.
-  PrefixPtr[1] = ID;
+  PrefixPtr[1] = ID.get();
 
   return Result;
 }

diff --git a/clang/lib/AST/DeclCXX.cpp b/clang/lib/AST/DeclCXX.cpp
@@ -57,7 +57,8 @@ using namespace clang;
 
 void AccessSpecDecl::anchor() {}
 
-AccessSpecDecl *AccessSpecDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+AccessSpecDecl *AccessSpecDecl::CreateDeserialized(ASTContext &C,
+                                                   GlobalDeclID ID) {
   return new (C, ID) AccessSpecDecl(EmptyShell());
 }
 
@@ -68,7 +69,7 @@ void LazyASTUnresolvedSet::getFromExternalSource(ASTContext &C) const {
 
   for (ASTUnresolvedSet::iterator I = Impl.begin(); I != Impl.end(); ++I)
     I.setDecl(cast<NamedDecl>(Source->GetExternalDecl(
-        reinterpret_cast<uintptr_t>(I.getDecl()) >> 2)));
+        GlobalDeclID(reinterpret_cast<uintptr_t>(I.getDecl()) >> 2))));
   Impl.Decls.setLazy(false);
 }
 
@@ -160,8 +161,8 @@ CXXRecordDecl::CreateLambda(const ASTContext &C, DeclContext *DC,
   return R;
 }
 
-CXXRecordDecl *
-CXXRecordDecl::CreateDeserialized(const ASTContext &C, Decl::DeclID ID) {
+CXXRecordDecl *CXXRecordDecl::CreateDeserialized(const ASTContext &C,
+                                                 GlobalDeclID ID) {
   auto *R = new (C, ID)
       CXXRecordDecl(CXXRecord, TagTypeKind::Struct, C, nullptr,
                     SourceLocation(), SourceLocation(), nullptr, nullptr);
@@ -2162,8 +2163,8 @@ CXXDeductionGuideDecl *CXXDeductionGuideDecl::Create(
                                            TInfo, EndLocation, Ctor, Kind);
 }
 
-CXXDeductionGuideDecl *CXXDeductionGuideDecl::CreateDeserialized(ASTContext &C,
-                                                                 Decl::DeclID ID) {
+CXXDeductionGuideDecl *
+CXXDeductionGuideDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   return new (C, ID) CXXDeductionGuideDecl(
       C, nullptr, SourceLocation(), ExplicitSpecifier(), DeclarationNameInfo(),
       QualType(), nullptr, SourceLocation(), nullptr,
@@ -2175,8 +2176,8 @@ RequiresExprBodyDecl *RequiresExprBodyDecl::Create(
   return new (C, DC) RequiresExprBodyDecl(C, DC, StartLoc);
 }
 
-RequiresExprBodyDecl *RequiresExprBodyDecl::CreateDeserialized(ASTContext &C,
-                                                               Decl::DeclID ID) {
+RequiresExprBodyDecl *
+RequiresExprBodyDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   return new (C, ID) RequiresExprBodyDecl(C, nullptr, SourceLocation());
 }
 
@@ -2281,7 +2282,8 @@ CXXMethodDecl::Create(ASTContext &C, CXXRecordDecl *RD, SourceLocation StartLoc,
       isInline, ConstexprKind, EndLocation, TrailingRequiresClause);
 }
 
-CXXMethodDecl *CXXMethodDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+CXXMethodDecl *CXXMethodDecl::CreateDeserialized(ASTContext &C,
+                                                 GlobalDeclID ID) {
   return new (C, ID) CXXMethodDecl(
       CXXMethod, C, nullptr, SourceLocation(), DeclarationNameInfo(),
       QualType(), nullptr, SC_None, false, false,
@@ -2699,7 +2701,7 @@ CXXConstructorDecl::CXXConstructorDecl(
 void CXXConstructorDecl::anchor() {}
 
 CXXConstructorDecl *CXXConstructorDecl::CreateDeserialized(ASTContext &C,
-                                                           Decl::DeclID ID,
+                                                           GlobalDeclID ID,
                                                            uint64_t AllocKind) {
   bool hasTrailingExplicit = static_cast<bool>(AllocKind & TAKHasTailExplicit);
   bool isInheritingConstructor =
@@ -2845,8 +2847,8 @@ bool CXXConstructorDecl::isSpecializationCopyingObject() const {
 
 void CXXDestructorDecl::anchor() {}
 
-CXXDestructorDecl *
-CXXDestructorDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+CXXDestructorDecl *CXXDestructorDecl::CreateDeserialized(ASTContext &C,
+                                                         GlobalDeclID ID) {
   return new (C, ID) CXXDestructorDecl(
       C, nullptr, SourceLocation(), DeclarationNameInfo(), QualType(), nullptr,
       false, false, false, ConstexprSpecKind::Unspecified, nullptr);
@@ -2877,8 +2879,8 @@ void CXXDestructorDecl::setOperatorDelete(FunctionDecl *OD, Expr *ThisArg) {
 
 void CXXConversionDecl::anchor() {}
 
-CXXConversionDecl *
-CXXConversionDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+CXXConversionDecl *CXXConversionDecl::CreateDeserialized(ASTContext &C,
+                                                         GlobalDeclID ID) {
   return new (C, ID) CXXConversionDecl(
       C, nullptr, SourceLocation(), DeclarationNameInfo(), QualType(), nullptr,
       false, false, ExplicitSpecifier(), ConstexprSpecKind::Unspecified,
@@ -2924,7 +2926,7 @@ LinkageSpecDecl *LinkageSpecDecl::Create(ASTContext &C, DeclContext *DC,
 }
 
 LinkageSpecDecl *LinkageSpecDecl::CreateDeserialized(ASTContext &C,
-                                                     Decl::DeclID ID) {
+                                                     GlobalDeclID ID) {
   return new (C, ID)
       LinkageSpecDecl(nullptr, SourceLocation(), SourceLocation(),
                       LinkageSpecLanguageIDs::C, false);
@@ -2946,7 +2948,7 @@ UsingDirectiveDecl *UsingDirectiveDecl::Create(ASTContext &C, DeclContext *DC,
 }
 
 UsingDirectiveDecl *UsingDirectiveDecl::CreateDeserialized(ASTContext &C,
-                                                           Decl::DeclID ID) {
+                                                           GlobalDeclID ID) {
   return new (C, ID) UsingDirectiveDecl(nullptr, SourceLocation(),
                                         SourceLocation(),
                                         NestedNameSpecifierLoc(),
@@ -2985,7 +2987,8 @@ NamespaceDecl *NamespaceDecl::Create(ASTContext &C, DeclContext *DC,
       NamespaceDecl(C, DC, Inline, StartLoc, IdLoc, Id, PrevDecl, Nested);
 }
 
-NamespaceDecl *NamespaceDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+NamespaceDecl *NamespaceDecl::CreateDeserialized(ASTContext &C,
+                                                 GlobalDeclID ID) {
   return new (C, ID) NamespaceDecl(C, nullptr, false, SourceLocation(),
                                    SourceLocation(), nullptr, nullptr, false);
 }
@@ -3046,8 +3049,8 @@ NamespaceAliasDecl *NamespaceAliasDecl::Create(ASTContext &C, DeclContext *DC,
                                         QualifierLoc, IdentLoc, Namespace);
 }
 
-NamespaceAliasDecl *
-NamespaceAliasDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+NamespaceAliasDecl *NamespaceAliasDecl::CreateDeserialized(ASTContext &C,
+                                                           GlobalDeclID ID) {
   return new (C, ID) NamespaceAliasDecl(C, nullptr, SourceLocation(),
                                         SourceLocation(), nullptr,
                                         NestedNameSpecifierLoc(),
@@ -3102,8 +3105,8 @@ UsingShadowDecl::UsingShadowDecl(Kind K, ASTContext &C, EmptyShell Empty)
     : NamedDecl(K, nullptr, SourceLocation(), DeclarationName()),
       redeclarable_base(C) {}
 
-UsingShadowDecl *
-UsingShadowDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+UsingShadowDecl *UsingShadowDecl::CreateDeserialized(ASTContext &C,
+                                                     GlobalDeclID ID) {
   return new (C, ID) UsingShadowDecl(UsingShadow, C, EmptyShell());
 }
 
@@ -3126,7 +3129,7 @@ ConstructorUsingShadowDecl::Create(ASTContext &C, DeclContext *DC,
 }
 
 ConstructorUsingShadowDecl *
-ConstructorUsingShadowDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+ConstructorUsingShadowDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   return new (C, ID) ConstructorUsingShadowDecl(C, EmptyShell());
 }
 
@@ -3174,7 +3177,7 @@ UsingDecl *UsingDecl::Create(ASTContext &C, DeclContext *DC, SourceLocation UL,
   return new (C, DC) UsingDecl(DC, UL, QualifierLoc, NameInfo, HasTypename);
 }
 
-UsingDecl *UsingDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+UsingDecl *UsingDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   return new (C, ID) UsingDecl(nullptr, SourceLocation(),
                                NestedNameSpecifierLoc(), DeclarationNameInfo(),
                                false);
@@ -3198,7 +3201,8 @@ UsingEnumDecl *UsingEnumDecl::Create(ASTContext &C, DeclContext *DC,
       UsingEnumDecl(DC, EnumType->getType()->getAsTagDecl()->getDeclName(), UL, EL, NL, EnumType);
 }
 
-UsingEnumDecl *UsingEnumDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+UsingEnumDecl *UsingEnumDecl::CreateDeserialized(ASTContext &C,
+                                                 GlobalDeclID ID) {
   return new (C, ID)
       UsingEnumDecl(nullptr, DeclarationName(), SourceLocation(),
                     SourceLocation(), SourceLocation(), nullptr);
@@ -3217,7 +3221,7 @@ UsingPackDecl *UsingPackDecl::Create(ASTContext &C, DeclContext *DC,
   return new (C, DC, Extra) UsingPackDecl(DC, InstantiatedFrom, UsingDecls);
 }
 
-UsingPackDecl *UsingPackDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID,
+UsingPackDecl *UsingPackDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID,
                                                  unsigned NumExpansions) {
   size_t Extra = additionalSizeToAlloc<NamedDecl *>(NumExpansions);
   auto *Result =
@@ -3243,7 +3247,7 @@ UnresolvedUsingValueDecl::Create(ASTContext &C, DeclContext *DC,
 }
 
 UnresolvedUsingValueDecl *
-UnresolvedUsingValueDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+UnresolvedUsingValueDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   return new (C, ID) UnresolvedUsingValueDecl(nullptr, QualType(),
                                               SourceLocation(),
                                               NestedNameSpecifierLoc(),
@@ -3273,7 +3277,8 @@ UnresolvedUsingTypenameDecl::Create(ASTContext &C, DeclContext *DC,
 }
 
 UnresolvedUsingTypenameDecl *
-UnresolvedUsingTypenameDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+UnresolvedUsingTypenameDecl::CreateDeserialized(ASTContext &C,
+                                                GlobalDeclID ID) {
   return new (C, ID) UnresolvedUsingTypenameDecl(
       nullptr, SourceLocation(), SourceLocation(), NestedNameSpecifierLoc(),
       SourceLocation(), nullptr, SourceLocation());
@@ -3286,7 +3291,8 @@ UnresolvedUsingIfExistsDecl::Create(ASTContext &Ctx, DeclContext *DC,
 }
 
 UnresolvedUsingIfExistsDecl *
-UnresolvedUsingIfExistsDecl::CreateDeserialized(ASTContext &Ctx, Decl::DeclID ID) {
+UnresolvedUsingIfExistsDecl::CreateDeserialized(ASTContext &Ctx,
+                                                GlobalDeclID ID) {
   return new (Ctx, ID)
       UnresolvedUsingIfExistsDecl(nullptr, SourceLocation(), DeclarationName());
 }
@@ -3310,7 +3316,7 @@ StaticAssertDecl *StaticAssertDecl::Create(ASTContext &C, DeclContext *DC,
 }
 
 StaticAssertDecl *StaticAssertDecl::CreateDeserialized(ASTContext &C,
-                                                       Decl::DeclID ID) {
+                                                       GlobalDeclID ID) {
   return new (C, ID) StaticAssertDecl(nullptr, SourceLocation(), nullptr,
                                       nullptr, SourceLocation(), false);
 }
@@ -3332,7 +3338,7 @@ BindingDecl *BindingDecl::Create(ASTContext &C, DeclContext *DC,
   return new (C, DC) BindingDecl(DC, IdLoc, Id);
 }
 
-BindingDecl *BindingDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+BindingDecl *BindingDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   return new (C, ID) BindingDecl(nullptr, SourceLocation(), nullptr);
 }
 
@@ -3363,7 +3369,7 @@ DecompositionDecl *DecompositionDecl::Create(ASTContext &C, DeclContext *DC,
 }
 
 DecompositionDecl *DecompositionDecl::CreateDeserialized(ASTContext &C,
-                                                         Decl::DeclID ID,
+                                                         GlobalDeclID ID,
                                                          unsigned NumBindings) {
   size_t Extra = additionalSizeToAlloc<BindingDecl *>(NumBindings);
   auto *Result = new (C, ID, Extra)
@@ -3402,7 +3408,7 @@ MSPropertyDecl *MSPropertyDecl::Create(ASTContext &C, DeclContext *DC,
 }
 
 MSPropertyDecl *MSPropertyDecl::CreateDeserialized(ASTContext &C,
-                                                   Decl::DeclID ID) {
+                                                   GlobalDeclID ID) {
   return new (C, ID) MSPropertyDecl(nullptr, SourceLocation(),
                                     DeclarationName(), QualType(), nullptr,
                                     SourceLocation(), nullptr, nullptr);
@@ -3419,7 +3425,7 @@ MSGuidDecl *MSGuidDecl::Create(const ASTContext &C, QualType T, Parts P) {
   return new (C, DC) MSGuidDecl(DC, T, P);
 }
 
-MSGuidDecl *MSGuidDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+MSGuidDecl *MSGuidDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   return new (C, ID) MSGuidDecl(nullptr, QualType(), Parts());
 }
 
@@ -3529,7 +3535,7 @@ UnnamedGlobalConstantDecl::Create(const ASTContext &C, QualType T,
 }
 
 UnnamedGlobalConstantDecl *
-UnnamedGlobalConstantDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+UnnamedGlobalConstantDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   return new (C, ID)
       UnnamedGlobalConstantDecl(C, nullptr, QualType(), APValue());
 }

diff --git a/clang/lib/AST/DeclFriend.cpp b/clang/lib/AST/DeclFriend.cpp
@@ -62,7 +62,7 @@ FriendDecl *FriendDecl::Create(ASTContext &C, DeclContext *DC,
   return FD;
 }
 
-FriendDecl *FriendDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID,
+FriendDecl *FriendDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID,
                                            unsigned FriendTypeNumTPLists) {
   std::size_t Extra =
       additionalSizeToAlloc<TemplateParameterList *>(FriendTypeNumTPLists);

diff --git a/clang/lib/AST/DeclObjC.cpp b/clang/lib/AST/DeclObjC.cpp
@@ -862,7 +862,8 @@ ObjCMethodDecl *ObjCMethodDecl::Create(
       isImplicitlyDeclared, isDefined, impControl, HasRelatedResultType);
 }
 
-ObjCMethodDecl *ObjCMethodDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+ObjCMethodDecl *ObjCMethodDecl::CreateDeserialized(ASTContext &C,
+                                                   GlobalDeclID ID) {
   return new (C, ID) ObjCMethodDecl(SourceLocation(), SourceLocation(),
                                     Selector(), QualType(), nullptr, nullptr);
 }
@@ -1486,7 +1487,7 @@ ObjCTypeParamDecl *ObjCTypeParamDecl::Create(ASTContext &ctx, DeclContext *dc,
 }
 
 ObjCTypeParamDecl *ObjCTypeParamDecl::CreateDeserialized(ASTContext &ctx,
-                                                         Decl::DeclID ID) {
+                                                         GlobalDeclID ID) {
   return new (ctx, ID) ObjCTypeParamDecl(ctx, nullptr,
                                          ObjCTypeParamVariance::Invariant,
                                          SourceLocation(), 0, SourceLocation(),
@@ -1551,7 +1552,7 @@ ObjCInterfaceDecl *ObjCInterfaceDecl::Create(
 }
 
 ObjCInterfaceDecl *ObjCInterfaceDecl::CreateDeserialized(const ASTContext &C,
-                                                         Decl::DeclID ID) {
+                                                         GlobalDeclID ID) {
   auto *Result = new (C, ID)
       ObjCInterfaceDecl(C, nullptr, SourceLocation(), nullptr, nullptr,
                         SourceLocation(), nullptr, false);
@@ -1865,7 +1866,7 @@ ObjCIvarDecl *ObjCIvarDecl::Create(ASTContext &C, ObjCContainerDecl *DC,
                                   synthesized);
 }
 
-ObjCIvarDecl *ObjCIvarDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+ObjCIvarDecl *ObjCIvarDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   return new (C, ID) ObjCIvarDecl(nullptr, SourceLocation(), SourceLocation(),
                                   nullptr, QualType(), nullptr,
                                   ObjCIvarDecl::None, nullptr, false);
@@ -1914,7 +1915,7 @@ ObjCAtDefsFieldDecl
 }
 
 ObjCAtDefsFieldDecl *ObjCAtDefsFieldDecl::CreateDeserialized(ASTContext &C,
-                                                             Decl::DeclID ID) {
+                                                             GlobalDeclID ID) {
   return new (C, ID) ObjCAtDefsFieldDecl(nullptr, SourceLocation(),
                                          SourceLocation(), nullptr, QualType(),
                                          nullptr);
@@ -1949,7 +1950,7 @@ ObjCProtocolDecl *ObjCProtocolDecl::Create(ASTContext &C, DeclContext *DC,
 }
 
 ObjCProtocolDecl *ObjCProtocolDecl::CreateDeserialized(ASTContext &C,
-                                                       Decl::DeclID ID) {
+                                                       GlobalDeclID ID) {
   ObjCProtocolDecl *Result =
       new (C, ID) ObjCProtocolDecl(C, nullptr, nullptr, SourceLocation(),
                                    SourceLocation(), nullptr);
@@ -2148,7 +2149,7 @@ ObjCCategoryDecl *ObjCCategoryDecl::Create(
 }
 
 ObjCCategoryDecl *ObjCCategoryDecl::CreateDeserialized(ASTContext &C,
-                                                       Decl::DeclID ID) {
+                                                       GlobalDeclID ID) {
   return new (C, ID) ObjCCategoryDecl(nullptr, SourceLocation(),
                                       SourceLocation(), SourceLocation(),
                                       nullptr, nullptr, nullptr);
@@ -2188,8 +2189,8 @@ ObjCCategoryImplDecl *ObjCCategoryImplDecl::Create(
                                           atStartLoc, CategoryNameLoc);
 }
 
-ObjCCategoryImplDecl *ObjCCategoryImplDecl::CreateDeserialized(ASTContext &C,
-                                                               Decl::DeclID ID) {
+ObjCCategoryImplDecl *
+ObjCCategoryImplDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   return new (C, ID) ObjCCategoryImplDecl(nullptr, nullptr, nullptr,
                                           SourceLocation(), SourceLocation(),
                                           SourceLocation());
@@ -2296,7 +2297,7 @@ ObjCImplementationDecl::Create(ASTContext &C, DeclContext *DC,
 }
 
 ObjCImplementationDecl *
-ObjCImplementationDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+ObjCImplementationDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   return new (C, ID) ObjCImplementationDecl(nullptr, nullptr, nullptr,
                                             SourceLocation(), SourceLocation());
 }
@@ -2339,7 +2340,7 @@ ObjCCompatibleAliasDecl::Create(ASTContext &C, DeclContext *DC,
 }
 
 ObjCCompatibleAliasDecl *
-ObjCCompatibleAliasDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+ObjCCompatibleAliasDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   return new (C, ID) ObjCCompatibleAliasDecl(nullptr, SourceLocation(),
                                              nullptr, nullptr);
 }
@@ -2360,7 +2361,7 @@ ObjCPropertyDecl::Create(ASTContext &C, DeclContext *DC, SourceLocation L,
 }
 
 ObjCPropertyDecl *ObjCPropertyDecl::CreateDeserialized(ASTContext &C,
-                                                       Decl::DeclID ID) {
+                                                       GlobalDeclID ID) {
   return new (C, ID) ObjCPropertyDecl(nullptr, SourceLocation(), nullptr,
                                       SourceLocation(), SourceLocation(),
                                       QualType(), nullptr, None);
@@ -2392,8 +2393,8 @@ ObjCPropertyImplDecl *ObjCPropertyImplDecl::Create(ASTContext &C,
                                           ivarLoc);
 }
 
-ObjCPropertyImplDecl *ObjCPropertyImplDecl::CreateDeserialized(ASTContext &C,
-                                                               Decl::DeclID ID) {
+ObjCPropertyImplDecl *
+ObjCPropertyImplDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   return new (C, ID) ObjCPropertyImplDecl(nullptr, SourceLocation(),
                                           SourceLocation(), nullptr, Dynamic,
                                           nullptr, SourceLocation());

diff --git a/clang/lib/AST/DeclOpenMP.cpp b/clang/lib/AST/DeclOpenMP.cpp
@@ -36,7 +36,7 @@ OMPThreadPrivateDecl *OMPThreadPrivateDecl::Create(ASTContext &C,
 }
 
 OMPThreadPrivateDecl *OMPThreadPrivateDecl::CreateDeserialized(ASTContext &C,
-                                                               Decl::DeclID ID,
+                                                               GlobalDeclID ID,
                                                                unsigned N) {
   return OMPDeclarativeDirective::createEmptyDirective<OMPThreadPrivateDecl>(
       C, ID, 0, N);
@@ -63,7 +63,8 @@ OMPAllocateDecl *OMPAllocateDecl::Create(ASTContext &C, DeclContext *DC,
   return D;
 }
 
-OMPAllocateDecl *OMPAllocateDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID,
+OMPAllocateDecl *OMPAllocateDecl::CreateDeserialized(ASTContext &C,
+                                                     GlobalDeclID ID,
                                                      unsigned NVars,
                                                      unsigned NClauses) {
   return OMPDeclarativeDirective::createEmptyDirective<OMPAllocateDecl>(
@@ -89,7 +90,8 @@ OMPRequiresDecl *OMPRequiresDecl::Create(ASTContext &C, DeclContext *DC,
                                                                    L);
 }
 
-OMPRequiresDecl *OMPRequiresDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID,
+OMPRequiresDecl *OMPRequiresDecl::CreateDeserialized(ASTContext &C,
+                                                     GlobalDeclID ID,
                                                      unsigned N) {
   return OMPDeclarativeDirective::createEmptyDirective<OMPRequiresDecl>(
       C, ID, N, 0, SourceLocation());
@@ -117,7 +119,7 @@ OMPDeclareReductionDecl *OMPDeclareReductionDecl::Create(
 }
 
 OMPDeclareReductionDecl *
-OMPDeclareReductionDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+OMPDeclareReductionDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   return new (C, ID) OMPDeclareReductionDecl(
       OMPDeclareReduction, /*DC=*/nullptr, SourceLocation(), DeclarationName(),
       QualType(), /*PrevDeclInScope=*/nullptr);
@@ -148,7 +150,7 @@ OMPDeclareMapperDecl *OMPDeclareMapperDecl::Create(
 }
 
 OMPDeclareMapperDecl *OMPDeclareMapperDecl::CreateDeserialized(ASTContext &C,
-                                                               Decl::DeclID ID,
+                                                               GlobalDeclID ID,
                                                                unsigned N) {
   return OMPDeclarativeDirective::createEmptyDirective<OMPDeclareMapperDecl>(
       C, ID, N, 1, SourceLocation(), DeclarationName(), QualType(),
@@ -179,7 +181,7 @@ OMPCapturedExprDecl *OMPCapturedExprDecl::Create(ASTContext &C, DeclContext *DC,
 }
 
 OMPCapturedExprDecl *OMPCapturedExprDecl::CreateDeserialized(ASTContext &C,
-                                                             Decl::DeclID ID) {
+                                                             GlobalDeclID ID) {
   return new (C, ID) OMPCapturedExprDecl(C, nullptr, nullptr, QualType(),
                                          /*TInfo=*/nullptr, SourceLocation());
 }

diff --git a/clang/lib/AST/DeclTemplate.cpp b/clang/lib/AST/DeclTemplate.cpp
@@ -337,9 +337,10 @@ void RedeclarableTemplateDecl::loadLazySpecializationsImpl() const {
   CommonBase *CommonBasePtr = getMostRecentDecl()->getCommonPtr();
   if (CommonBasePtr->LazySpecializations) {
     ASTContext &Context = getASTContext();
-    Decl::DeclID *Specs = CommonBasePtr->LazySpecializations;
+    GlobalDeclID *Specs = CommonBasePtr->LazySpecializations;
     CommonBasePtr->LazySpecializations = nullptr;
-    for (uint32_t I = 0, N = *Specs++; I != N; ++I)
+    unsigned SpecSize = (*Specs++).get();
+    for (unsigned I = 0; I != SpecSize; ++I)
       (void)Context.getExternalSource()->GetExternalDecl(Specs[I]);
   }
 }
@@ -417,8 +418,8 @@ FunctionTemplateDecl::Create(ASTContext &C, DeclContext *DC, SourceLocation L,
   return TD;
 }
 
-FunctionTemplateDecl *FunctionTemplateDecl::CreateDeserialized(ASTContext &C,
-                                                               Decl::DeclID ID) {
+FunctionTemplateDecl *
+FunctionTemplateDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   return new (C, ID) FunctionTemplateDecl(C, nullptr, SourceLocation(),
                                           DeclarationName(), nullptr, nullptr);
 }
@@ -503,7 +504,7 @@ ClassTemplateDecl *ClassTemplateDecl::Create(ASTContext &C, DeclContext *DC,
 }
 
 ClassTemplateDecl *ClassTemplateDecl::CreateDeserialized(ASTContext &C,
-                                                         Decl::DeclID ID) {
+                                                         GlobalDeclID ID) {
   return new (C, ID) ClassTemplateDecl(C, nullptr, SourceLocation(),
                                        DeclarationName(), nullptr, nullptr);
 }
@@ -652,14 +653,14 @@ TemplateTypeParmDecl *TemplateTypeParmDecl::Create(
 }
 
 TemplateTypeParmDecl *
-TemplateTypeParmDecl::CreateDeserialized(const ASTContext &C, Decl::DeclID ID) {
+TemplateTypeParmDecl::CreateDeserialized(const ASTContext &C, GlobalDeclID ID) {
   return new (C, ID)
       TemplateTypeParmDecl(nullptr, SourceLocation(), SourceLocation(), nullptr,
                            false, false, std::nullopt);
 }
 
 TemplateTypeParmDecl *
-TemplateTypeParmDecl::CreateDeserialized(const ASTContext &C, Decl::DeclID ID,
+TemplateTypeParmDecl::CreateDeserialized(const ASTContext &C, GlobalDeclID ID,
                                          bool HasTypeConstraint) {
   return new (C, ID,
               additionalSizeToAlloc<TypeConstraint>(HasTypeConstraint ? 1 : 0))
@@ -759,7 +760,7 @@ NonTypeTemplateParmDecl *NonTypeTemplateParmDecl::Create(
 }
 
 NonTypeTemplateParmDecl *
-NonTypeTemplateParmDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID,
+NonTypeTemplateParmDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID,
                                             bool HasTypeConstraint) {
   return new (C, ID, additionalSizeToAlloc<std::pair<QualType,
                                                      TypeSourceInfo *>,
@@ -770,7 +771,7 @@ NonTypeTemplateParmDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID,
 }
 
 NonTypeTemplateParmDecl *
-NonTypeTemplateParmDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID,
+NonTypeTemplateParmDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID,
                                             unsigned NumExpandedTypes,
                                             bool HasTypeConstraint) {
   auto *NTTP =
@@ -836,13 +837,13 @@ TemplateTemplateParmDecl::Create(const ASTContext &C, DeclContext *DC,
 }
 
 TemplateTemplateParmDecl *
-TemplateTemplateParmDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+TemplateTemplateParmDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   return new (C, ID) TemplateTemplateParmDecl(nullptr, SourceLocation(), 0, 0,
                                               false, nullptr, false, nullptr);
 }
 
 TemplateTemplateParmDecl *
-TemplateTemplateParmDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID,
+TemplateTemplateParmDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID,
                                              unsigned NumExpansions) {
   auto *TTP =
       new (C, ID, additionalSizeToAlloc<TemplateParameterList *>(NumExpansions))
@@ -949,7 +950,7 @@ ClassTemplateSpecializationDecl::Create(ASTContext &Context, TagKind TK,
 
 ClassTemplateSpecializationDecl *
 ClassTemplateSpecializationDecl::CreateDeserialized(ASTContext &C,
-                                                    Decl::DeclID ID) {
+                                                    GlobalDeclID ID) {
   auto *Result =
     new (C, ID) ClassTemplateSpecializationDecl(C, ClassTemplateSpecialization);
   Result->setMayHaveOutOfDateDef(false);
@@ -1035,8 +1036,7 @@ ConceptDecl *ConceptDecl::Create(ASTContext &C, DeclContext *DC,
   return TD;
 }
 
-ConceptDecl *ConceptDecl::CreateDeserialized(ASTContext &C,
-                                             Decl::DeclID ID) {
+ConceptDecl *ConceptDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   ConceptDecl *Result = new (C, ID) ConceptDecl(nullptr, SourceLocation(),
                                                 DeclarationName(),
                                                 nullptr, nullptr);
@@ -1070,7 +1070,7 @@ ImplicitConceptSpecializationDecl *ImplicitConceptSpecializationDecl::Create(
 
 ImplicitConceptSpecializationDecl *
 ImplicitConceptSpecializationDecl::CreateDeserialized(
-    const ASTContext &C, Decl::DeclID ID, unsigned NumTemplateArgs) {
+    const ASTContext &C, GlobalDeclID ID, unsigned NumTemplateArgs) {
   return new (C, ID, additionalSizeToAlloc<TemplateArgument>(NumTemplateArgs))
       ImplicitConceptSpecializationDecl(EmptyShell{}, NumTemplateArgs);
 }
@@ -1133,7 +1133,7 @@ Create(ASTContext &Context, TagKind TK,DeclContext *DC,
 
 ClassTemplatePartialSpecializationDecl *
 ClassTemplatePartialSpecializationDecl::CreateDeserialized(ASTContext &C,
-                                                           Decl::DeclID ID) {
+                                                           GlobalDeclID ID) {
   auto *Result = new (C, ID) ClassTemplatePartialSpecializationDecl(C);
   Result->setMayHaveOutOfDateDef(false);
   return Result;
@@ -1160,7 +1160,7 @@ FriendTemplateDecl::Create(ASTContext &Context, DeclContext *DC,
 }
 
 FriendTemplateDecl *FriendTemplateDecl::CreateDeserialized(ASTContext &C,
-                                                           Decl::DeclID ID) {
+                                                           GlobalDeclID ID) {
   return new (C, ID) FriendTemplateDecl(EmptyShell());
 }
 
@@ -1179,8 +1179,8 @@ TypeAliasTemplateDecl::Create(ASTContext &C, DeclContext *DC, SourceLocation L,
   return TD;
 }
 
-TypeAliasTemplateDecl *TypeAliasTemplateDecl::CreateDeserialized(ASTContext &C,
-                                                                 Decl::DeclID ID) {
+TypeAliasTemplateDecl *
+TypeAliasTemplateDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   return new (C, ID) TypeAliasTemplateDecl(C, nullptr, SourceLocation(),
                                            DeclarationName(), nullptr, nullptr);
 }
@@ -1218,7 +1218,7 @@ VarTemplateDecl *VarTemplateDecl::Create(ASTContext &C, DeclContext *DC,
 }
 
 VarTemplateDecl *VarTemplateDecl::CreateDeserialized(ASTContext &C,
-                                                     Decl::DeclID ID) {
+                                                     GlobalDeclID ID) {
   return new (C, ID) VarTemplateDecl(C, nullptr, SourceLocation(),
                                      DeclarationName(), nullptr, nullptr);
 }
@@ -1340,7 +1340,8 @@ VarTemplateSpecializationDecl *VarTemplateSpecializationDecl::Create(
 }
 
 VarTemplateSpecializationDecl *
-VarTemplateSpecializationDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+VarTemplateSpecializationDecl::CreateDeserialized(ASTContext &C,
+                                                  GlobalDeclID ID) {
   return new (C, ID)
       VarTemplateSpecializationDecl(VarTemplateSpecialization, C);
 }
@@ -1432,7 +1433,7 @@ VarTemplatePartialSpecializationDecl::Create(
 
 VarTemplatePartialSpecializationDecl *
 VarTemplatePartialSpecializationDecl::CreateDeserialized(ASTContext &C,
-                                                         Decl::DeclID ID) {
+                                                         GlobalDeclID ID) {
   return new (C, ID) VarTemplatePartialSpecializationDecl(C);
 }
 
@@ -1546,7 +1547,7 @@ TemplateParamObjectDecl *TemplateParamObjectDecl::Create(const ASTContext &C,
 }
 
 TemplateParamObjectDecl *
-TemplateParamObjectDecl::CreateDeserialized(ASTContext &C, Decl::DeclID ID) {
+TemplateParamObjectDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   auto *TPOD = new (C, ID) TemplateParamObjectDecl(nullptr, QualType(), APValue());
   C.addDestruction(&TPOD->Value);
   return TPOD;

diff --git a/clang/lib/AST/Expr.cpp b/clang/lib/AST/Expr.cpp
@@ -3680,7 +3680,7 @@ bool Expr::HasSideEffects(const ASTContext &Ctx,
   case ParenExprClass:
   case ArraySubscriptExprClass:
   case MatrixSubscriptExprClass:
-  case OMPArraySectionExprClass:
+  case ArraySectionExprClass:
   case OMPArrayShapingExprClass:
   case OMPIteratorExprClass:
   case MemberExprClass:
@@ -5060,9 +5060,9 @@ QualType AtomicExpr::getValueType() const {
   return T;
 }
 
-QualType OMPArraySectionExpr::getBaseOriginalType(const Expr *Base) {
+QualType ArraySectionExpr::getBaseOriginalType(const Expr *Base) {
   unsigned ArraySectionCount = 0;
-  while (auto *OASE = dyn_cast<OMPArraySectionExpr>(Base->IgnoreParens())) {
+  while (auto *OASE = dyn_cast<ArraySectionExpr>(Base->IgnoreParens())) {
     Base = OASE->getBase();
     ++ArraySectionCount;
   }

diff --git a/clang/lib/AST/ExprClassification.cpp b/clang/lib/AST/ExprClassification.cpp
@@ -145,7 +145,7 @@ static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E) {
   case Expr::FunctionParmPackExprClass:
   case Expr::MSPropertyRefExprClass:
   case Expr::MSPropertySubscriptExprClass:
-  case Expr::OMPArraySectionExprClass:
+  case Expr::ArraySectionExprClass:
   case Expr::OMPArrayShapingExprClass:
   case Expr::OMPIteratorExprClass:
     return Cl::CL_LValue;

diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
@@ -16130,7 +16130,7 @@ static ICEDiag CheckICE(const Expr* E, const ASTContext &Ctx) {
   case Expr::StringLiteralClass:
   case Expr::ArraySubscriptExprClass:
   case Expr::MatrixSubscriptExprClass:
-  case Expr::OMPArraySectionExprClass:
+  case Expr::ArraySectionExprClass:
   case Expr::OMPArrayShapingExprClass:
   case Expr::OMPIteratorExprClass:
   case Expr::MemberExprClass:

diff --git a/clang/lib/AST/ExternalASTSource.cpp b/clang/lib/AST/ExternalASTSource.cpp
@@ -68,7 +68,7 @@ bool ExternalASTSource::layoutRecordType(
   return false;
 }
 
-Decl *ExternalASTSource::GetExternalDecl(Decl::DeclID ID) { return nullptr; }
+Decl *ExternalASTSource::GetExternalDecl(GlobalDeclID ID) { return nullptr; }
 
 Selector ExternalASTSource::GetExternalSelector(uint32_t ID) {
   return Selector();

diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp
@@ -4715,7 +4715,7 @@ void CXXNameMangler::mangleExpression(const Expr *E, unsigned Arity,
   case Expr::MSPropertySubscriptExprClass:
   case Expr::TypoExprClass: // This should no longer exist in the AST by now.
   case Expr::RecoveryExprClass:
-  case Expr::OMPArraySectionExprClass:
+  case Expr::ArraySectionExprClass:
   case Expr::OMPArrayShapingExprClass:
   case Expr::OMPIteratorExprClass:
   case Expr::CXXInheritedCtorInitExprClass:

diff --git a/clang/lib/AST/NSAPI.cpp b/clang/lib/AST/NSAPI.cpp
@@ -462,7 +462,7 @@ NSAPI::getNSNumberFactoryMethodKind(QualType T) const {
   case BuiltinType::PseudoObject:
   case BuiltinType::BuiltinFn:
   case BuiltinType::IncompleteMatrixIdx:
-  case BuiltinType::OMPArraySection:
+  case BuiltinType::ArraySection:
   case BuiltinType::OMPArrayShaping:
   case BuiltinType::OMPIterator:
   case BuiltinType::BFloat16: