[NFC] Split ProtocolDispatchStrategy out of MetadataValues.h.

This allows us to avoid rebuilding most of the compiler
whenever we add a new ABI constant.

Author: rjmccall

cmake/modules/AddSwift.cmake

@@ -630,3 +630,9 @@ macro(add_swift_tool_symlink name dest component)
   add_llvm_tool_symlink(${name} ${dest} ALWAYS_GENERATE)
   llvm_install_symlink(${name} ${dest} ALWAYS_GENERATE COMPONENT ${component})
 endmacro()
+
+# Declare that files in this library are built with LLVM's support
+# libraries available.
+macro(set_swift_llvm_is_available)
+  add_compile_options(-DSWIFT_LLVM_SUPPORT_IS_AVAILABLE)
+endmacro()

include/swift/ABI/MetadataValues.h

@@ -20,10 +20,10 @@
 #define SWIFT_ABI_METADATAVALUES_H
 
 #include "swift/ABI/KeyPath.h"
+#include "swift/ABI/ProtocolDispatchStrategy.h"
 #include "swift/AST/Ownership.h"
 #include "swift/Basic/LLVM.h"
 #include "swift/Basic/FlagSet.h"
-#include "swift/Runtime/Unreachable.h"
 
 #include <stdlib.h>
 #include <stdint.h>
@@ -410,20 +410,6 @@ enum class SpecialProtocol: uint8_t {
   Error = 1,
 };
 
-/// Identifiers for protocol method dispatch strategies.
-enum class ProtocolDispatchStrategy: uint8_t {
-  /// Uses ObjC method dispatch.
-  ///
-  /// This must be 0 for ABI compatibility with Objective-C protocol_t records.
-  ObjC = 0,
-  
-  /// Uses Swift protocol witness table dispatch.
-  ///
-  /// To invoke methods of this protocol, a pointer to a protocol witness table
-  /// corresponding to the protocol conformance must be available.
-  Swift = 1,
-};
-
 /// Flags for protocol descriptors.
 class ProtocolDescriptorFlags {
   typedef uint32_t int_type;
@@ -486,18 +472,7 @@ class ProtocolDescriptorFlags {
 
   /// Does the protocol require a witness table for method dispatch?
   bool needsWitnessTable() const {
-    return needsWitnessTable(getDispatchStrategy());
-  }
-  
-  static bool needsWitnessTable(ProtocolDispatchStrategy strategy) {
-    switch (strategy) {
-    case ProtocolDispatchStrategy::ObjC:
-      return false;
-    case ProtocolDispatchStrategy::Swift:
-      return true;
-    }
-
-    swift_runtime_unreachable("Unhandled ProtocolDispatchStrategy in switch.");
+    return swift::protocolRequiresWitnessTable(getDispatchStrategy());
   }
 
   /// Return the identifier if this is a special runtime-known protocol.

include/swift/ABI/ProtocolDispatchStrategy.h

@@ -0,0 +1,54 @@
+//===--- ProtocolDispatchStrategy.h - ---------------------------*- C++ -*-===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+//
+// This header declares the ProtocolDispatchStrategy enum and some
+// related operations.  It's split out because we would otherwise need
+// to include MetadataValues.h in some relatively central headers.s
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SWIFT_ABI_PROTOCOLDISPATCHSTRATEGY_H
+#define SWIFT_ABI_PROTOCOLDISPATCHSTRATEGY_H
+
+#include "swift/Runtime/Unreachable.h"
+
+namespace swift {
+
+/// Identifiers for protocol method dispatch strategies.
+enum class ProtocolDispatchStrategy: uint8_t {
+  /// Uses ObjC method dispatch.
+  ///
+  /// This must be 0 for ABI compatibility with Objective-C protocol_t records.
+  ObjC = 0,
+  
+  /// Uses Swift protocol witness table dispatch.
+  ///
+  /// To invoke methods of this protocol, a pointer to a protocol witness table
+  /// corresponding to the protocol conformance must be available.
+  Swift = 1,
+};
+
+/// Does a protocol using the given strategy require a witness table?
+inline bool protocolRequiresWitnessTable(ProtocolDispatchStrategy strategy) {
+  switch (strategy) {
+  case ProtocolDispatchStrategy::ObjC:
+    return false;
+  case ProtocolDispatchStrategy::Swift:
+    return true;
+  }
+
+  swift_runtime_unreachable("Unhandled ProtocolDispatchStrategy in switch.");
+}
+
+}
+
+#endif

include/swift/SIL/TypeLowering.h

@@ -13,7 +13,7 @@
 #ifndef SWIFT_SIL_TYPELOWERING_H
 #define SWIFT_SIL_TYPELOWERING_H
 
-#include "swift/ABI/MetadataValues.h"
+#include "swift/ABI/ProtocolDispatchStrategy.h"
 #include "swift/AST/CaptureInfo.h"
 #include "swift/AST/Module.h"
 #include "swift/SIL/AbstractionPattern.h"
@@ -792,8 +792,7 @@ class TypeConverter {
 
   /// True if a protocol uses witness tables for dynamic dispatch.
   static bool protocolRequiresWitnessTable(ProtocolDecl *P) {
-    return ProtocolDescriptorFlags::needsWitnessTable
-             (getProtocolDispatchStrategy(P));
+    return swift::protocolRequiresWitnessTable(getProtocolDispatchStrategy(P));
   }
 
   /// True if a type is passed indirectly at +0 when used as the "self"

lib/IRGen/IRGen.cpp

@@ -16,6 +16,7 @@
 
 #define DEBUG_TYPE "irgen"
 #include "IRGenModule.h"
+#include "swift/ABI/MetadataValues.h"
 #include "swift/AST/DiagnosticsIRGen.h"
 #include "swift/AST/IRGenOptions.h"
 #include "swift/AST/IRGenRequests.h"