diff --git a/clang/include/clang/AST/ComparisonCategories.h b/clang/include/clang/AST/ComparisonCategories.h
--- a/clang/include/clang/AST/ComparisonCategories.h
+++ b/clang/include/clang/AST/ComparisonCategories.h
@@ -19,6 +19,7 @@
 #include "llvm/ADT/DenseMap.h"
 #include <array>
 #include <cassert>
+#include <vector>
 
 namespace llvm {
   class StringRef;
diff --git a/llvm/include/llvm/ADT/ArrayRef.h b/llvm/include/llvm/ADT/ArrayRef.h
--- a/llvm/include/llvm/ADT/ArrayRef.h
+++ b/llvm/include/llvm/ADT/ArrayRef.h
@@ -26,6 +26,8 @@
 
 namespace llvm {
 
+  template<typename T> struct DenseMapInfo;
+
   /// ArrayRef - Represent a constant reference to an array (0 or more elements
   /// consecutively in memory), i.e. a start pointer and a length.  It allows
   /// various APIs to take consecutive elements easily and conveniently.
@@ -569,6 +571,35 @@
     return hash_combine_range(S.begin(), S.end());
   }
 
+  // Provide DenseMapInfo for ArrayRefs.
+  template <typename T> struct DenseMapInfo<ArrayRef<T>> {
+    static inline ArrayRef<T> getEmptyKey() {
+      return ArrayRef<T>(
+          reinterpret_cast<const T *>(~static_cast<uintptr_t>(0)), size_t(0));
+    }
+
+    static inline ArrayRef<T> getTombstoneKey() {
+      return ArrayRef<T>(
+          reinterpret_cast<const T *>(~static_cast<uintptr_t>(1)), size_t(0));
+    }
+
+    static unsigned getHashValue(ArrayRef<T> Val) {
+      assert(Val.data() != getEmptyKey().data() &&
+             "Cannot hash the empty key!");
+      assert(Val.data() != getTombstoneKey().data() &&
+             "Cannot hash the tombstone key!");
+      return (unsigned)(hash_value(Val));
+    }
+
+    static bool isEqual(ArrayRef<T> LHS, ArrayRef<T> RHS) {
+      if (RHS.data() == getEmptyKey().data())
+        return LHS.data() == getEmptyKey().data();
+      if (RHS.data() == getTombstoneKey().data())
+        return LHS.data() == getTombstoneKey().data();
+      return LHS == RHS;
+    }
+  };
+
 } // end namespace llvm
 
 #endif // LLVM_ADT_ARRAYREF_H
diff --git a/llvm/include/llvm/ADT/DenseMapInfo.h b/llvm/include/llvm/ADT/DenseMapInfo.h
--- a/llvm/include/llvm/ADT/DenseMapInfo.h
+++ b/llvm/include/llvm/ADT/DenseMapInfo.h
@@ -13,9 +13,7 @@
 #ifndef LLVM_ADT_DENSEMAPINFO_H
 #define LLVM_ADT_DENSEMAPINFO_H
 
-#include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/Hashing.h"
-#include "llvm/ADT/StringRef.h"
 #include <cassert>
 #include <cstddef>
 #include <cstdint>
@@ -284,62 +282,6 @@
   }
 };
 
-// Provide DenseMapInfo for StringRefs.
-template <> struct DenseMapInfo<StringRef> {
-  static inline StringRef getEmptyKey() {
-    return StringRef(reinterpret_cast<const char *>(~static_cast<uintptr_t>(0)),
-                     0);
-  }
-
-  static inline StringRef getTombstoneKey() {
-    return StringRef(reinterpret_cast<const char *>(~static_cast<uintptr_t>(1)),
-                     0);
-  }
-
-  static unsigned getHashValue(StringRef Val) {
-    assert(Val.data() != getEmptyKey().data() && "Cannot hash the empty key!");
-    assert(Val.data() != getTombstoneKey().data() &&
-           "Cannot hash the tombstone key!");
-    return (unsigned)(hash_value(Val));
-  }
-
-  static bool isEqual(StringRef LHS, StringRef RHS) {
-    if (RHS.data() == getEmptyKey().data())
-      return LHS.data() == getEmptyKey().data();
-    if (RHS.data() == getTombstoneKey().data())
-      return LHS.data() == getTombstoneKey().data();
-    return LHS == RHS;
-  }
-};
-
-// Provide DenseMapInfo for ArrayRefs.
-template <typename T> struct DenseMapInfo<ArrayRef<T>> {
-  static inline ArrayRef<T> getEmptyKey() {
-    return ArrayRef<T>(reinterpret_cast<const T *>(~static_cast<uintptr_t>(0)),
-                       size_t(0));
-  }
-
-  static inline ArrayRef<T> getTombstoneKey() {
-    return ArrayRef<T>(reinterpret_cast<const T *>(~static_cast<uintptr_t>(1)),
-                       size_t(0));
-  }
-
-  static unsigned getHashValue(ArrayRef<T> Val) {
-    assert(Val.data() != getEmptyKey().data() && "Cannot hash the empty key!");
-    assert(Val.data() != getTombstoneKey().data() &&
-           "Cannot hash the tombstone key!");
-    return (unsigned)(hash_value(Val));
-  }
-
-  static bool isEqual(ArrayRef<T> LHS, ArrayRef<T> RHS) {
-    if (RHS.data() == getEmptyKey().data())
-      return LHS.data() == getEmptyKey().data();
-    if (RHS.data() == getTombstoneKey().data())
-      return LHS.data() == getTombstoneKey().data();
-    return LHS == RHS;
-  }
-};
-
 template <> struct DenseMapInfo<hash_code> {
   static inline hash_code getEmptyKey() { return hash_code(-1); }
   static inline hash_code getTombstoneKey() { return hash_code(-2); }
diff --git a/llvm/include/llvm/ADT/StringRef.h b/llvm/include/llvm/ADT/StringRef.h
--- a/llvm/include/llvm/ADT/StringRef.h
+++ b/llvm/include/llvm/ADT/StringRef.h
@@ -35,6 +35,7 @@
   class APInt;
   class hash_code;
   template <typename T> class SmallVectorImpl;
+  template <typename T> struct DenseMapInfo;
   class StringRef;
 
   /// Helper functions for StringRef::getAsInteger.
@@ -925,6 +926,35 @@
   LLVM_NODISCARD
   hash_code hash_value(StringRef S);
 
+  // Provide DenseMapInfo for StringRefs.
+  template <> struct DenseMapInfo<StringRef> {
+    static inline StringRef getEmptyKey() {
+      return StringRef(
+          reinterpret_cast<const char *>(~static_cast<uintptr_t>(0)), 0);
+    }
+
+    static inline StringRef getTombstoneKey() {
+      return StringRef(
+          reinterpret_cast<const char *>(~static_cast<uintptr_t>(1)), 0);
+    }
+
+    static unsigned getHashValue(StringRef Val) {
+      assert(Val.data() != getEmptyKey().data() &&
+             "Cannot hash the empty key!");
+      assert(Val.data() != getTombstoneKey().data() &&
+             "Cannot hash the tombstone key!");
+      return (unsigned)(hash_value(Val));
+    }
+
+    static bool isEqual(StringRef LHS, StringRef RHS) {
+      if (RHS.data() == getEmptyKey().data())
+        return LHS.data() == getEmptyKey().data();
+      if (RHS.data() == getTombstoneKey().data())
+        return LHS.data() == getTombstoneKey().data();
+      return LHS == RHS;
+    }
+  };
+
 } // end namespace llvm
 
 #endif // LLVM_ADT_STRINGREF_H
diff --git a/llvm/include/llvm/IR/PassInstrumentation.h b/llvm/include/llvm/IR/PassInstrumentation.h
--- a/llvm/include/llvm/IR/PassInstrumentation.h
+++ b/llvm/include/llvm/IR/PassInstrumentation.h
@@ -54,6 +54,7 @@
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringMap.h"
 #include <type_traits>
+#include <vector>
 
 namespace llvm {
 
diff --git a/llvm/include/llvm/Support/Threading.h b/llvm/include/llvm/Support/Threading.h
--- a/llvm/include/llvm/Support/Threading.h
+++ b/llvm/include/llvm/Support/Threading.h
@@ -17,6 +17,7 @@
 #include "llvm/ADT/BitVector.h"
 #include "llvm/ADT/FunctionExtras.h"
 #include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/StringRef.h"
 #include "llvm/Config/llvm-config.h" // for LLVM_ON_UNIX
 #include "llvm/Support/Compiler.h"
 #include <ciso646> // So we can check the C++ standard lib macros.
diff --git a/llvm/lib/CodeGen/AsmPrinter/WinException.h b/llvm/lib/CodeGen/AsmPrinter/WinException.h
--- a/llvm/lib/CodeGen/AsmPrinter/WinException.h
+++ b/llvm/lib/CodeGen/AsmPrinter/WinException.h
@@ -14,6 +14,7 @@
 #define LLVM_LIB_CODEGEN_ASMPRINTER_WIN64EXCEPTION_H
 
 #include "EHStreamer.h"
+#include <vector>
 
 namespace llvm {
 class GlobalValue;
diff --git a/llvm/lib/CodeGen/MBFIWrapper.cpp b/llvm/lib/CodeGen/MBFIWrapper.cpp
--- a/llvm/lib/CodeGen/MBFIWrapper.cpp
+++ b/llvm/lib/CodeGen/MBFIWrapper.cpp
@@ -11,8 +11,9 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/CodeGen/MBFIWrapper.h"
+#include "llvm/ADT/Optional.h"
 #include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
+#include "llvm/CodeGen/MBFIWrapper.h"
 
 using namespace llvm;
 
diff --git a/llvm/lib/MC/StringTableBuilder.cpp b/llvm/lib/MC/StringTableBuilder.cpp
--- a/llvm/lib/MC/StringTableBuilder.cpp
+++ b/llvm/lib/MC/StringTableBuilder.cpp
@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/MC/StringTableBuilder.h"
+#include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/CachedHashString.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringRef.h"
diff --git a/llvm/lib/Support/SmallPtrSet.cpp b/llvm/lib/Support/SmallPtrSet.cpp
--- a/llvm/lib/Support/SmallPtrSet.cpp
+++ b/llvm/lib/Support/SmallPtrSet.cpp
@@ -13,8 +13,9 @@
 
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/DenseMapInfo.h"
-#include "llvm/Support/MathExtras.h"
 #include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/MathExtras.h"
+#include "llvm/Support/MemAlloc.h"
 #include <algorithm>
 #include <cassert>
 #include <cstdlib>
diff --git a/llvm/lib/Target/AMDGPU/AMDGPUGlobalISelUtils.h b/llvm/lib/Target/AMDGPU/AMDGPUGlobalISelUtils.h
--- a/llvm/lib/Target/AMDGPU/AMDGPUGlobalISelUtils.h
+++ b/llvm/lib/Target/AMDGPU/AMDGPUGlobalISelUtils.h
@@ -9,6 +9,7 @@
 #ifndef LLVM_LIB_TARGET_AMDGPU_AMDGPUGLOBALISELUTILS_H
 #define LLVM_LIB_TARGET_AMDGPU_AMDGPUGLOBALISELUTILS_H
 
+#include "llvm/ADT/ArrayRef.h"
 #include "llvm/CodeGen/Register.h"
 #include <utility>
 
diff --git a/llvm/tools/llvm-c-test/echo.cpp b/llvm/tools/llvm-c-test/echo.cpp
--- a/llvm/tools/llvm-c-test/echo.cpp
+++ b/llvm/tools/llvm-c-test/echo.cpp
@@ -18,6 +18,7 @@
 #include "llvm-c/DebugInfo.h"
 #include "llvm-c/Target.h"
 #include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/SmallVector.h"
 #include "llvm/Support/ErrorHandling.h"
 
 #include <stdio.h>
diff --git a/mlir/include/mlir/IR/AffineExpr.h b/mlir/include/mlir/IR/AffineExpr.h
--- a/mlir/include/mlir/IR/AffineExpr.h
+++ b/mlir/include/mlir/IR/AffineExpr.h
@@ -17,6 +17,7 @@
 #include "mlir/Support/LLVM.h"
 #include "llvm/ADT/DenseMapInfo.h"
 #include "llvm/Support/Casting.h"
+#include <functional>
 #include <type_traits>
 
 namespace mlir {
diff --git a/mlir/include/mlir/IR/DialectInterface.h b/mlir/include/mlir/IR/DialectInterface.h
--- a/mlir/include/mlir/IR/DialectInterface.h
+++ b/mlir/include/mlir/IR/DialectInterface.h
@@ -11,6 +11,7 @@
 
 #include "mlir/Support/TypeID.h"
 #include "llvm/ADT/DenseSet.h"
+#include "llvm/ADT/STLExtras.h"
 
 namespace mlir {
 class Dialect;
diff --git a/mlir/include/mlir/Support/InterfaceSupport.h b/mlir/include/mlir/Support/InterfaceSupport.h
--- a/mlir/include/mlir/Support/InterfaceSupport.h
+++ b/mlir/include/mlir/Support/InterfaceSupport.h
@@ -14,6 +14,7 @@
 #define MLIR_SUPPORT_INTERFACESUPPORT_H
 
 #include "mlir/Support/TypeID.h"
+#include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/Support/TypeName.h"
 
diff --git a/mlir/include/mlir/Support/StorageUniquer.h b/mlir/include/mlir/Support/StorageUniquer.h
--- a/mlir/include/mlir/Support/StorageUniquer.h
+++ b/mlir/include/mlir/Support/StorageUniquer.h
@@ -12,7 +12,9 @@
 #include "mlir/Support/LLVM.h"
 #include "mlir/Support/LogicalResult.h"
 #include "mlir/Support/TypeID.h"
+#include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/DenseSet.h"
+#include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Allocator.h"
 
 namespace mlir {