Load runtime library modules from SDK

With this change, swiftc will still look for standard library and overlay modules in ../lib/swift (relative to the compiler), but if it doesn’t find them there, it will now look in usr/lib/swift in the SDK.

Author: beccadax

lib/Frontend/CompilerInvocation.cpp

@@ -49,6 +49,8 @@ static void updateRuntimeLibraryPaths(SearchPathOptions &SearchPathOpts,
   llvm::sys::path::append(LibPath, getPlatformNameForTriple(Triple));
   SearchPathOpts.RuntimeLibraryPath = LibPath.str();
 
+  // Set up the import paths containing the swiftmodules for the libraries in
+  // RuntimeLibraryPath.
   SearchPathOpts.RuntimeLibraryImportPaths.clear();
 
   // If this is set, we don't want any runtime import paths.
@@ -58,6 +60,12 @@ static void updateRuntimeLibraryPaths(SearchPathOptions &SearchPathOpts,
   if (!Triple.isOSDarwin())
     llvm::sys::path::append(LibPath, swift::getMajorArchitectureName(Triple));
   SearchPathOpts.RuntimeLibraryImportPaths.push_back(LibPath.str());
+
+  if (!SearchPathOpts.SDKPath.empty()) {
+    LibPath = SearchPathOpts.SDKPath;
+    llvm::sys::path::append(LibPath, "usr", "lib", "swift");
+    SearchPathOpts.RuntimeLibraryImportPaths.push_back(LibPath.str());
+  }
 }
 
 void CompilerInvocation::setRuntimeResourcePath(StringRef Path) {

test/Serialization/runtime-import-from-sdk.swift

@@ -0,0 +1,47 @@
+/// Tests the fallback behavior for runtime library import paths. These should
+/// prefer the resource directory, but fall back to the SDK.
+
+// Assumption: We build the standard library with the compiler, so the default
+// resource directory will contain a swiftmodule for the standard library.
+
+// %t/good-sdk contains a loadable standard library.
+// RUN: %empty-directory(%t/good-sdk/usr/lib/swift)
+// RUN: cp -r %platform-module-dir/Swift.swiftmodule %t/good-sdk/usr/lib/swift/Swift.swiftmodule
+
+// %t/bad-sdk contains an invalid standard library that cannot be loaded.
+// RUN: %empty-directory(%t/bad-sdk/usr/lib/swift/Swift.swiftmodule)
+// RUN: touch %t/bad-sdk/usr/lib/swift/Swift.swiftmodule/garbage-garbage-garbage.swiftmodule
+
+// %t/empty-toolchain does not contain a standard library.
+// RUN: %empty-directory(%t/empty-toolchain/usr/lib/swift)
+
+// FIXME: Until we have private imports, we need SwiftShims in the toolchain.
+// RUN: cp -r %test-resource-dir/shims %t/empty-toolchain/usr/lib/swift/shims
+
+// If the compiler's resource directory does not contain a runtime swiftmodule,
+// we should fall back to the SDK.
+
+// RUN: %empty-directory(%t/mcp)
+// RUN: %target-swift-frontend(mock-sdk: -sdk %t/good-sdk) -resource-dir %t/empty-toolchain/usr/lib/swift -module-cache-path %t/mcp -typecheck -verify %s
+
+// If the compiler's resource directory *does* contain a runtime swiftmodule, we
+// should *not* use the one in the SDK. (We assume that the resource directory
+// built with this compiler does contain a standard library.)
+
+// RUN: %empty-directory(%t/mcp)
+// RUN: %target-swift-frontend(mock-sdk: -sdk %t/bad-sdk) -module-cache-path %t/mcp -typecheck -verify %s
+
+// If neither the resource directory nor the SDK contains a runtime swiftmodule,
+// loading should fail. This just proves that we aren't getting runtime imports
+// some other way.
+
+// FIXME: We can't properly test this on a non-Darwin platform because we'll get
+// the same error message for "unloadable standard library" and "no standard
+// library". (SR-10097)
+// REQUIRES: objc_interop
+
+// RUN: %empty-directory(%t/mcp)
+// RUN: not %target-swift-frontend(mock-sdk: -sdk %t/bad-sdk) -resource-dir %t/empty-toolchain/usr/lib/swift -module-cache-path %t/mcp -typecheck %s 2>&1 | %FileCheck %s
+// CHECK: error: could not find module 'Swift' for target '{{.*}}'; found: garbage-garbage-garbage
+
+let x: Int = 1

test/lit.cfg

@@ -310,6 +310,7 @@ else:
     resource_dir_opt = ""
 stdlib_resource_dir_opt = resource_dir_opt
 sourcekitd_framework_dir = config.swift_lib_dir
+config.substitutions.append( ('%test-resource-dir', test_resource_dir) )
 lit_config.note('Using resource dir: ' + test_resource_dir)
 
 # Parse the variant triple.