Merge pull request swiftlang#22806 from slavapestov/imported-conformance-corner-case

SIL: Don't serialize imported conformances nested in non-public types

Author: slavapestov

lib/SIL/SILWitnessTable.cpp

@@ -12,10 +12,11 @@
 //
 // This file defines the SILWitnessTable class, which is used to map a protocol
 // conformance for a type to its implementing SILFunctions. This information is
-// (FIXME will be) used by IRGen to create witness tables for protocol dispatch.
+// used by IRGen to create witness tables for protocol dispatch.
+//
 // It can also be used by generic specialization and existential
-// devirtualization passes to promote witness_method and protocol_method
-// instructions to static function_refs.
+// devirtualization passes to promote witness_method instructions to static
+// function_refs.
 //
 //===----------------------------------------------------------------------===//
 
@@ -24,7 +25,6 @@
 #include "swift/AST/ASTMangler.h"
 #include "swift/AST/Module.h"
 #include "swift/AST/ProtocolConformance.h"
-#include "swift/ClangImporter/ClangModule.h"
 #include "swift/SIL/SILModule.h"
 #include "llvm/ADT/SmallString.h"
 
@@ -172,11 +172,6 @@ bool SILWitnessTable::conformanceIsSerialized(
   if (normalConformance && normalConformance->isResilient())
     return false;
 
-  // Serialize witness tables for conformances synthesized by
-  // the ClangImporter.
-  if (isa<ClangModuleUnit>(conformance->getDeclContext()->getModuleScopeContext()))
-    return true;
-
   if (conformance->getProtocol()->getEffectiveAccess() < AccessLevel::Public)
     return false;
 

lib/SILGen/SILGenType.cpp

@@ -487,9 +487,18 @@ class SILGenConformance : public SILGenWitnessTable<SILGenConformance> {
     } else {
       // This is the "real" rule; the above case should go away once we
       // figure out what's going on.
-      witnessLinkage = (witnessSerialized
-                        ? SILLinkage::Shared
-                        : SILLinkage::Private);
+
+      // Normally witness thunks can be private.
+      witnessLinkage = SILLinkage::Private;
+
+      // Unless the witness table is going to be serialized.
+      if (witnessSerialized)
+        witnessLinkage = SILLinkage::Shared;
+
+      // Or even if its not serialized, it might be for an imported
+      // conformance in which case it can be emitted multiple times.
+      if (Linkage == SILLinkage::Shared)
+        witnessLinkage = SILLinkage::Shared;
     }
 
     SILFunction *witnessFn = SGM.emitProtocolWitness(

test/SILGen/Inputs/objc_witnesses_serialized.h

@@ -0,0 +1,6 @@
+@class Public;
+@class Internal;
+
+enum InternalInner { a, b, c } __attribute__((swift_name("Public.Inner")));
+enum PublicInner { d, e, f } __attribute__((swift_name("Internal.Inner")));
+enum TopLevel { g, h, i };

test/SILGen/objc_witnesses_serialized.swift

@@ -0,0 +1,35 @@
+// RUN: %target-swift-emit-silgen -sdk %S/Inputs -I %S/Inputs -enable-source-import %s -import-objc-header %S/Inputs/objc_witnesses_serialized.h | %FileCheck %s
+
+// REQUIRES: objc_interop
+
+import Foundation
+
+func useRawRepresentable<T : RawRepresentable>(_: T) {}
+
+// FIXME: getEffectiveClangContext() is broken and checks
+// for an explicit '@objc' attribute.
+
+@objc public class Public : NSObject {
+  func takesInner(_ value: Inner) {
+    useRawRepresentable(value)
+  }
+}
+
+@objc internal class Internal : NSObject {
+  func takesInner(_ value: Inner) {
+    useRawRepresentable(value)
+  }
+}
+
+func takesTopLevel(_ value: TopLevel) {
+  useRawRepresentable(value)
+}
+
+// CHECK-LABEL: sil shared [transparent] [serialized] [thunk] [ossa] @$sSo13InternalInnerVSYSCSY8rawValuexSg03RawD0Qz_tcfCTW : $@convention(witness_method: RawRepresentable) (@in UInt32, @thick Public.Inner.Type) -> @out Optional<Public.Inner>
+// CHECK-LABEL: sil shared [transparent] [serialized] [thunk] [ossa] @$sSo13InternalInnerVSYSCSY8rawValue03RawD0QzvgTW : $@convention(witness_method: RawRepresentable) (@in_guaranteed Public.Inner) -> @out UInt32
+
+// CHECK-LABEL: sil shared [transparent] [thunk] [ossa] @$sSo11PublicInnerVSYSCSY8rawValuexSg03RawD0Qz_tcfCTW : $@convention(witness_method: RawRepresentable) (@in UInt32, @thick Internal.Inner.Type) -> @out Optional<Internal.Inner>
+// CHECK-LABEL: sil shared [transparent] [thunk] [ossa] @$sSo11PublicInnerVSYSCSY8rawValue03RawD0QzvgTW : $@convention(witness_method: RawRepresentable) (@in_guaranteed Internal.Inner) -> @out UInt32
+
+// CHECK-LABEL: sil shared [transparent] [serialized] [thunk] [ossa] @$sSo8TopLevelVSYSCSY8rawValuexSg03RawD0Qz_tcfCTW : $@convention(witness_method: RawRepresentable) (@in UInt32, @thick TopLevel.Type) -> @out Optional<TopLevel>
+// CHECK-LABEL: sil shared [transparent] [serialized] [thunk] [ossa] @$sSo8TopLevelVSYSCSY8rawValue03RawD0QzvgTW : $@convention(witness_method: RawRepresentable) (@in_guaranteed TopLevel) -> @out UInt32