SIL: serialize computed effects for @alwaysEmitIntoClient functions, even if library evolution is turned on.

This is possible because no copy of the function is emitted in the original module.

Author: eeckstein

lib/Serialization/SerializeSIL.cpp

@@ -529,8 +529,16 @@ void SILSerializer::writeSILFunction(const SILFunction &F, bool DeclOnly) {
 
   unsigned numAttrs = NoBody ? 0 : F.getSpecializeAttrs().size();
   auto resilience = F.getModule().getSwiftModule()->getResilienceStrategy();
-  bool serializeDerivedEffects = (resilience != ResilienceStrategy::Resilient) &&
-                                 !F.hasSemanticsAttr("optimize.no.crossmodule");
+  bool serializeDerivedEffects =
+    // We must not serialize computed effects if library evolution is turned on,
+    // because the copy of the function, which is emitted into the current module,
+    // might have different effects in different versions of the library.
+    (resilience != ResilienceStrategy::Resilient ||
+    // But we can serialize computed effects for @alwaysEmitIntoClient functions,
+    // even when library evolution is enabled, because no copy of the function is
+    // emitted in the original module.
+    F.getLinkage() == SILLinkage::PublicNonABI) &&
+    !F.hasSemanticsAttr("optimize.no.crossmodule");
 
   F.visitArgEffects(
     [&](int effectIdx, int argumentIndex, bool isDerived) {

test/SIL/Serialization/effects.sil

@@ -0,0 +1,31 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend %s -module-name=NonLE -emit-module -o %t/NonLE.swiftmodule
+// RUN: %target-swift-frontend %s -module-name=LE -enable-library-evolution -emit-module -o %t/LE.swiftmodule
+// RUN: %target-sil-opt %t/NonLE.swiftmodule | %FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-NONLE
+// RUN: %target-sil-opt %t/LE.swiftmodule | %FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-LE
+
+sil_stage canonical
+
+import Swift
+import Builtin
+
+// CHECK-LABEL:      sil [serialized] [canonical] [ossa] @public_func :
+// CHECK-NONLE-NEXT: [global: ]
+// CHECK-NEXT:       bb0:
+sil [serialized] [ossa] @public_func : $@convention(thin) () -> () {
+[global: ]
+bb0:
+  %r = tuple ()
+  return %r
+}
+
+// CHECK-LABEL:      sil non_abi [serialized] [canonical] [ossa] @public_non_abi_func :
+// CHECK-NEXT:       [global: ]
+// CHECK-NEXT:       bb0:
+sil non_abi [serialized] [ossa] @public_non_abi_func : $@convention(thin) () -> () {
+[global: ]
+bb0:
+  %r = tuple ()
+  return %r
+}
+