SILGen: Fix bug with NSString import-as-member globals

This is not really the right fix if we want to have physically
addressed lvalues support bridging in general, but doing so
requires adding a new LValue component type and doing a bunch
more refactoring, so just hack in a narrow fix for now since
it only seems to occur in one case.

Fixes <rdar://problem/34913892>.

Author: slavapestov

lib/SILGen/SILGenLValue.cpp

@@ -3213,6 +3213,9 @@ RValue SILGenFunction::emitLoadOfLValue(SILLocation loc, LValue &&src,
   // Any writebacks should be scoped to after the load.
   FormalEvaluationScope scope(*this);
 
+  // We shouldn't need to re-abstract here, but we might have to bridge.
+  // This should only happen if we have a global variable of NSString type.
+  auto origFormalType = src.getOrigFormalType();
   auto substFormalType = src.getSubstFormalType();
   auto &rvalueTL = getTypeLowering(src.getTypeOfRValue());
 
@@ -3226,6 +3229,7 @@ RValue SILGenFunction::emitLoadOfLValue(SILLocation loc, LValue &&src,
              .offset(*this, loc, addr, AccessKind::Read);
     return RValue(*this, loc, substFormalType,
                   emitLoad(loc, addr.getValue(),
+                           origFormalType, substFormalType,
                            rvalueTL, C, IsNotTake,
                            isBaseGuaranteed));
   }

test/IDE/Inputs/custom-modules/ImportAsMemberClass.h

@@ -32,4 +32,15 @@ UnavailableDefaultInit * _Nonnull MakeUnavailableDefaultInit(void);
 __attribute__((swift_name("UnavailableDefaultInitSub.init()")))
 UnavailableDefaultInitSub * _Nonnull MakeUnavailableDefaultInitSub(void);
 
+#pragma clang assume_nonnull begin
+
+extern NSString * PKPandaCutenessFactor __attribute__((swift_name("Panda.cutenessFactor")));
+extern NSString * _Nullable PKPandaCuddlynessFactor __attribute__((swift_name("Panda.cuddlynessFactor")));
+
+__attribute__((swift_name("Panda")))
+@interface PKPanda : NSObject
+@end
+
+#pragma clang assume_nonnull end
+
 #endif

test/SILGen/import_as_member.swift

@@ -1,42 +1,64 @@
-// RUN: %target-swift-frontend -emit-silgen -I %S/../IDE/Inputs/custom-modules %s 2>&1 | %FileCheck --check-prefix=SIL %s
+// RUN: %target-swift-frontend -emit-silgen -I %S/../IDE/Inputs/custom-modules %s | %FileCheck %s
 // REQUIRES: objc_interop
 import ImportAsMember.A
 import ImportAsMember.Class
 
 public func returnGlobalVar() -> Double {
 	return Struct1.globalVar
 }
-// SIL-LABEL: sil {{.*}}returnGlobalVar{{.*}} () -> Double {
-// SIL:   %0 = global_addr @IAMStruct1GlobalVar : $*Double
-// SIL:   [[READ:%.*]] = begin_access [read] [dynamic] %0 : $*Double
-// SIL:   [[VAL:%.*]] = load [trivial] [[READ]] : $*Double
-// SIL:   return [[VAL]] : $Double
-// SIL-NEXT: }
-
-// SIL-LABEL: sil {{.*}}anchor{{.*}} () -> () {
-func anchor() {}
-
-// SIL-LABEL: sil {{.*}}useClass{{.*}}
-// SIL: bb0([[D:%[0-9]+]] : $Double, [[OPTS:%[0-9]+]] : $SomeClass.Options):
+// CHECK-LABEL: sil {{.*}}returnGlobalVar{{.*}} () -> Double {
+// CHECK:   %0 = global_addr @IAMStruct1GlobalVar : $*Double
+// CHECK:   [[READ:%.*]] = begin_access [read] [dynamic] %0 : $*Double
+// CHECK:   [[VAL:%.*]] = load [trivial] [[READ]] : $*Double
+// CHECK:   return [[VAL]] : $Double
+// CHECK-NEXT: }
+
+// N.B. Whether by design or due to a bug, nullable NSString globals
+// still import as non-null.
+public func returnStringGlobalVar() -> String {
+  return Panda.cutenessFactor
+}
+// CHECK-LABEL: sil {{.*}}returnStringGlobalVar{{.*}} () -> @owned String {
+// CHECK:   %0 = global_addr @PKPandaCutenessFactor : $*NSString
+// CHECK:   [[VAL:%.*]] = load [copy] %0 : $*NSString
+// CHECK:   [[BRIDGE:%.*]] = function_ref @_T0SS10FoundationE36_unconditionallyBridgeFromObjectiveCSSSo8NSStringCSgFZ
+// CHECK:   [[RESULT:%.*]] = apply [[BRIDGE]](
+// CHECK:   return [[RESULT]] : $String
+// CHECK-NEXT: }
+
+public func returnNullableStringGlobalVar() -> String? {
+  return Panda.cuddlynessFactor
+}
+// CHECK-LABEL: sil {{.*}}returnNullableStringGlobalVar{{.*}} () -> @owned Optional<String> {
+// CHECK:   %0 = global_addr @PKPandaCuddlynessFactor : $*NSString
+// CHECK:   [[VAL:%.*]] = load [copy] %0 : $*NSString
+// CHECK:   [[BRIDGE:%.*]] = function_ref @_T0SS10FoundationE36_unconditionallyBridgeFromObjectiveCSSSo8NSStringCSgFZ
+// CHECK:   [[RESULT:%.*]] = apply [[BRIDGE]](
+// CHECK:   [[SOME:%.*]] = enum $Optional<String>, #Optional.some!enumelt.1, [[RESULT]]
+// CHECK:   return [[SOME]] : $Optional<String>
+// CHECK-NEXT: }
+
+// CHECK-LABEL: sil {{.*}}useClass{{.*}}
+// CHECK: bb0([[D:%[0-9]+]] : $Double, [[OPTS:%[0-9]+]] : $SomeClass.Options):
 public func useClass(d: Double, opts: SomeClass.Options) {
-  // SIL: [[CTOR:%[0-9]+]] = function_ref @MakeIAMSomeClass : $@convention(c) (Double) -> @autoreleased SomeClass
-  // SIL: [[OBJ:%[0-9]+]] = apply [[CTOR]]([[D]])
+  // CHECK: [[CTOR:%[0-9]+]] = function_ref @MakeIAMSomeClass : $@convention(c) (Double) -> @autoreleased SomeClass
+  // CHECK: [[OBJ:%[0-9]+]] = apply [[CTOR]]([[D]])
   let o = SomeClass(value: d)
 
-  // SIL: [[APPLY_FN:%[0-9]+]] = function_ref @IAMSomeClassApplyOptions : $@convention(c) (SomeClass, SomeClass.Options) -> ()
-  // SIL: [[BORROWED_OBJ:%.*]] = begin_borrow [[OBJ]]
-  // SIL: apply [[APPLY_FN]]([[BORROWED_OBJ]], [[OPTS]])
-  // SIL: end_borrow [[BORROWED_OBJ]] from [[OBJ]]
-  // SIL: destroy_value [[OBJ]]
+  // CHECK: [[APPLY_FN:%[0-9]+]] = function_ref @IAMSomeClassApplyOptions : $@convention(c) (SomeClass, SomeClass.Options) -> ()
+  // CHECK: [[BORROWED_OBJ:%.*]] = begin_borrow [[OBJ]]
+  // CHECK: apply [[APPLY_FN]]([[BORROWED_OBJ]], [[OPTS]])
+  // CHECK: end_borrow [[BORROWED_OBJ]] from [[OBJ]]
+  // CHECK: destroy_value [[OBJ]]
   o.applyOptions(opts)
 }
 
 extension SomeClass {
-  // SIL-LABEL: sil hidden @_T0So9SomeClassC16import_as_memberEABSd6double_tcfc
-  // SIL: bb0([[DOUBLE:%[0-9]+]] : $Double
-  // SIL-NOT: value_metatype
-  // SIL: [[FNREF:%[0-9]+]] = function_ref @MakeIAMSomeClass
-  // SIL: apply [[FNREF]]([[DOUBLE]])
+  // CHECK-LABEL: sil hidden @_T0So9SomeClassC16import_as_memberEABSd6double_tcfc
+  // CHECK: bb0([[DOUBLE:%[0-9]+]] : $Double
+  // CHECK-NOT: value_metatype
+  // CHECK: [[FNREF:%[0-9]+]] = function_ref @MakeIAMSomeClass
+  // CHECK: apply [[FNREF]]([[DOUBLE]])
   convenience init(double: Double) {
     self.init(value: double)
   }
@@ -47,6 +69,3 @@ public func useSpecialInit() -> Struct1 {
   // return Struct1(specialLabel:())
 }
 
-public func useGlobal() -> Double {
-  return Struct1.globalVar
-}