[embedded] Skip EagerSpecializer on embedded Swift

Author: kubamracek

lib/SILOptimizer/PassManager/PassPipeline.cpp

@@ -683,7 +683,14 @@ static void addPerfEarlyModulePassPipeline(SILPassPipelinePlan &P) {
 static void addHighLevelFunctionPipeline(SILPassPipelinePlan &P) {
   P.startPipeline("HighLevel,Function+EarlyLoopOpt",
                   true /*isFunctionPassPipeline*/);
-  P.addEagerSpecializer();
+
+  // Skip EagerSpecializer on embedded Swift, which already specializes
+  // everything. Otherwise this would create metatype references for functions
+  // with @_specialize attribute and those are incompatible with Emebdded Swift.
+  if (!P.getOptions().EmbeddedSwift) {
+    P.addEagerSpecializer();
+  }
+
   P.addObjCBridgingOptimization();
 
   addFunctionPasses(P, OptimizationLevelKind::HighLevel);

test/embedded/specialize-attrs2.swift

@@ -0,0 +1,20 @@
+// RUN: %target-run-simple-swift(-parse-as-library -Onone -enable-experimental-feature Embedded -runtime-compatibility-version none -wmo -Xfrontend -disable-objc-interop -Xlinker -dead_strip) | %FileCheck %s
+// RUN: %target-run-simple-swift(-parse-as-library -O -enable-experimental-feature Embedded -runtime-compatibility-version none -wmo -Xfrontend -disable-objc-interop -Xlinker -dead_strip) | %FileCheck %s
+// RUN: %target-run-simple-swift(-parse-as-library -Osize -enable-experimental-feature Embedded -runtime-compatibility-version none -wmo -Xfrontend -disable-objc-interop -Xlinker -dead_strip) | %FileCheck %s
+
+// REQUIRES: swift_in_compiler
+// REQUIRES: executable_test
+// REQUIRES: optimized_stdlib
+// REQUIRES: OS=macosx
+
+@main
+struct Main {
+  static func main() {
+    let chars: [Character] = ["a", "b", "c"]
+    let s = Substring.init(chars)
+    print(s)
+    print("OK!")
+  }
+}
+
+// CHECK: OK!