[Macros] Add default plugin paths for Darwin SDKs and platforms.

Corresponding to swiftlang/swift-driver#1377, this
adds some default plugin paths for Darwin SDKs and platforms.
Fixes rdar://110819604.

Author: DougGregor

lib/Driver/DarwinToolChains.cpp

@@ -620,12 +620,49 @@ void toolchains::Darwin::addCommonFrontendArgs(
   }
 }
 
+/// Add the frontend arguments needed to find external plugins in standard
+/// locations based on the base path.
+static void addExternalPluginFrontendArgs(
+    StringRef basePath, const llvm::opt::ArgList &inputArgs,
+    llvm::opt::ArgStringList &arguments) {
+  // Plugin server: $BASE/usr/bin/swift-plugin-server
+  SmallString<128> pluginServer;
+  llvm::sys::path::append(
+      pluginServer, basePath, "usr", "bin", "swift-plugin-server");
+
+  SmallString<128> pluginDir;
+  llvm::sys::path::append(pluginDir, basePath, "usr", "lib");
+  llvm::sys::path::append(pluginDir, "swift", "host", "plugins");
+  arguments.push_back("-external-plugin-path");
+  arguments.push_back(inputArgs.MakeArgString(pluginDir + "#" + pluginServer));
+
+  pluginDir.clear();
+  llvm::sys::path::append(pluginDir, basePath, "usr", "local", "lib");
+  llvm::sys::path::append(pluginDir, "swift", "host", "plugins");
+  arguments.push_back("-external-plugin-path");
+  arguments.push_back(inputArgs.MakeArgString(pluginDir + "#" + pluginServer));
+}
+
 void toolchains::Darwin::addPlatformSpecificPluginFrontendArgs(
     const OutputInfo &OI,
     const CommandOutput &output,
     const llvm::opt::ArgList &inputArgs,
     llvm::opt::ArgStringList &arguments) const {
-  
+  // Add SDK-relative directories for plugins.
+  if (!OI.SDKPath.empty()) {
+    addExternalPluginFrontendArgs(OI.SDKPath, inputArgs, arguments);
+  }
+
+  // Add platform-relative directories for plugins.
+  if (!OI.SDKPath.empty()) {
+    SmallString<128> platformPath;
+    llvm::sys::path::append(platformPath, OI.SDKPath);
+    llvm::sys::path::remove_filename(platformPath); // specific SDK
+    llvm::sys::path::remove_filename(platformPath); // SDKs
+    llvm::sys::path::remove_filename(platformPath); // Developer
+    llvm::sys::path::append(platformPath, "Developer");
+    addExternalPluginFrontendArgs(platformPath, inputArgs, arguments);
+  }
 }
 
 ToolChain::InvocationInfo
@@ -702,7 +739,7 @@ toolchains::Darwin::constructInvocation(const DynamicLinkJobAction &job,
   }
 
   if (context.Args.hasArg(options::OPT_enable_app_extension)) {
-    // Keep this string fixed in case the option used by the
+    // Keep this string fixed in case the option used by thez
     // compiler itself changes.
     Arguments.push_back("-application_extension");
   }

lib/Driver/ToolChains.h

@@ -53,6 +53,12 @@ class LLVM_LIBRARY_VISIBILITY Darwin : public ToolChain {
       const llvm::opt::ArgList &inputArgs,
       llvm::opt::ArgStringList &arguments) const override;
 
+  void addPlatformSpecificPluginFrontendArgs(
+      const OutputInfo &OI,
+      const CommandOutput &output,
+      const llvm::opt::ArgList &inputArgs,
+      llvm::opt::ArgStringList &arguments) const override;
+
   InvocationInfo constructInvocation(const InterpretJobAction &job,
                                      const JobContext &context) const override;
   InvocationInfo constructInvocation(const DynamicLinkJobAction &job,

test/Driver/compiler_plugin_path_macosx.swift

@@ -0,0 +1,24 @@
+// RUN: %swiftc_driver -driver-print-jobs -target x86_64-apple-macosx10.9 %s 2>^1 | %FileCheck %s
+// REQUIRES: OS=macosx
+
+// CHECK: -external-plugin-path
+// CHECK-SAME: .sdk/usr/lib/swift/host/plugins#
+// CHECK-SAME: .sdk/usr/bin/swift-plugin-server
+
+// CHECK-SAME: -external-plugin-path
+// CHECK-SAME: .sdk/usr/local/lib/swift/host/plugins#
+// CHECK-SAME: .sdk/usr/bin/swift-plugin-server
+
+// CHECK-SAME: -external-plugin-path
+// CHECK-SAME: MacOSX.platform/Developer/usr/lib/swift/host/plugins#
+// CHECK-SAME: MacOSX.platform/Developer/usr/bin/swift-plugin-server
+
+// CHECK-SAME: -external-plugin-path
+// CHECK-SAME: MacOSX.platform/Developer/usr/local/lib/swift/host/plugins#
+// CHECK-SAME: MacOSX.platform/Developer/usr/bin/swift-plugin-server
+
+// CHECK-SAME: -plugin-path
+// CHECK-SAME: {{(/|\\\\)}}lib{{(/|\\\\)}}swift{{(/|\\\\)}}host{{(/|\\\\)}}plugins
+
+// CHECK-SAME: -plugin-path
+// CHECK-SAME: {{(/|\\\\)}}local{{(/|\\\\)}}lib{{(/|\\\\)}}swift{{(/|\\\\)}}host{{(/|\\\\)}}plugins

test/Driver/driver-compile.swift

@@ -75,7 +75,7 @@
 // COMPLEX: bin{{/|\\\\}}swift
 // COMPLEX: -c
 // COMPLEX: Driver{{/|\\\\}}driver-compile.swift
-// COMPLEX-DAG: -sdk {{.*}}/Inputs/clang-importer-sdk
+// COMPLEX-DAG: -sdk
 // COMPLEX-DAG: -foo -bar
 // COMPLEX-DAG: -Xllvm -baz
 // COMPLEX-DAG: -Xcc -garply

test/Driver/merge-module.swift

@@ -36,15 +36,16 @@
 // SIMPLE: -o main.swiftmodule
 
 
-// COMPLEX: {{bin(/|\\\\)swift(-frontend|c)?(\.exe)?"?}} -frontend
+// COMPLEX: -frontend
 // COMPLEX: -emit-module
 // COMPLEX-DAG: -emit-module-doc-path {{[^ ]*[/\\]}}merge-module-{{[^ ]*}}.swiftdoc
-// COMPLEX-DAG: -sdk {{.*}}/Inputs/clang-importer-sdk
+// COMPLEX-DAG: -sdk
+// COMPLEX-DAG /Inputs/clang-importer-sdk
 // COMPLEX-DAG: -foo -bar
 // COMPLEX-DAG: -F /path/to/frameworks -F /path/to/more/frameworks
 // COMPLEX-DAG: -I /path/to/headers -I path/to/more/headers
 // COMPLEX-DAG: -module-cache-path /tmp/modules
-// COMPLEX: {{bin(/|\\\\)swift(-frontend|c)?(\.exe)?"?}} -frontend
+// COMPLEX-DAG: -frontend
 // COMPLEX: -emit-module
 // COMPLEX-DAG: -F /path/to/frameworks -F /path/to/more/frameworks
 // COMPLEX-DAG: -I /path/to/headers -I path/to/more/headers

test/Driver/sdk.swift

@@ -12,7 +12,7 @@
 // OSX: bin{{/|\\\\}}swift
 // OSX: Driver{{/|\\\\}}sdk.swift
 // OSX: -sdk {{.*}}/Inputs/clang-importer-sdk
-// OSX-NEXT: bin{{/|\\\\}}swift
+// OSX: bin{{/|\\\\}}swift
 // OSX: -sdk {{.*}}/Inputs/clang-importer-sdk
 // OSX: {{.*}}.o{{[ "]}}
 // OSX: {{-syslibroot|--sysroot}} {{[^ ]*}}/Inputs/clang-importer-sdk