[6.0🍒][SILGen] Create thunks for non-throwing -> indirect error result conversions

lib/SIL/IR/TypeLowering.cpp

@@ -4664,6 +4664,12 @@ TypeConverter::checkFunctionForABIDifferences(SILModule &M,
       return ABIDifference::NeedsThunk;
   }
 
+  // Non-throwing functions and functions with indirect error result need thunk
+  // because of the trailing error result storage parameter.
+  if (fnTy1->hasIndirectErrorResult() != fnTy2->hasIndirectErrorResult()) {
+    return ABIDifference::NeedsThunk;
+  }
+
   // Asynchronous functions require a thunk if they differ in whether they
   // have an error result.
   if (fnTy1->hasErrorResult() != fnTy2->hasErrorResult() &&

test/SILGen/typed_throws_thunk.swift

@@ -0,0 +1,139 @@
+// RUN: %target-swift-emit-silgen %s | %FileCheck %s
+
+struct ConcreteError: Error {}
+
+func existentialPassThrough(_ body: () throws(Error) -> Void) throws(Error) {
+  try body()
+}
+
+func concretePassThrough(_ body: () throws(ConcreteError) -> Void) throws(ConcreteError) {
+  try body()
+}
+
+func genericPassThrough<X>(_ body: () throws(X) -> Void) throws(X) {
+  try body()
+}
+
+func neverThrow() {}
+func throwConcrete() throws(ConcreteError) {}
+func throwExistential() throws {}
+
+// CHECK-LABEL: sil{{.*}} @$s18typed_throws_thunk5test1yyKF
+func test1() throws {
+  // No thunk needed here because no indirect error result
+  // CHECK-NOT: function_ref thunk for
+  // CHECK: [[FN:%[0-9]+]] = function_ref @$s18typed_throws_thunk22existentialPassThroughyyyyKXEKF
+  // CHECK-NEXT: try_apply [[FN]]
+  try existentialPassThrough(neverThrow)
+}
+
+// CHECK-LABEL: sil{{.*}} @$s18typed_throws_thunk5test2yyKF
+func test2() throws {
+  // No thunk needed here because no indirect error result
+  // CHECK-NOT: function_ref thunk for
+  // CHECK: [[FN:%[0-9]+]] = function_ref @$s18typed_throws_thunk19concretePassThroughyyyyAA13ConcreteErrorVYKXEADYKF
+  // CHECK-NEXT: try_apply [[FN]]
+  try concretePassThrough(neverThrow)
+}
+
+// CHECK-LABEL: sil{{.*}} @$s18typed_throws_thunk5test3yyF
+func test3() {
+  // CHECK:      [[T1:%[0-9]+]] = function_ref @$s18typed_throws_thunk10neverThrowyyF
+  // CHECK-NEXT: [[T2:%[0-9]+]] = thin_to_thick_function [[T1]]
+  // CHECK-NEXT: [[T3:%[0-9]+]] = convert_escape_to_noescape [not_guaranteed] [[T2]]
+  // CHECK-NEXT: function_ref thunk for
+  // CHECK-NEXT: [[THUNK:%[0-9]+]] = function_ref @$sIg_s5NeverOIegzr_TR
+  // CHECK-NEXT: [[T4:%[0-9]+]] = partial_apply [callee_guaranteed] [[THUNK]]([[T3]])
+  // CHECK-NEXT: [[T5:%[0-9]+]] = convert_function [[T4]]
+  // CHECK-NEXT: [[T6:%[0-9]+]] = convert_escape_to_noescape [not_guaranteed] [[T5]]
+  // CHECK-NEXT: // function_ref genericPassThrough<A>(_:)
+  // CHECK-NEXT: [[T7:%[0-9]+]] = function_ref @$s18typed_throws_thunk18genericPassThroughyyyyxYKXExYKs5ErrorRzlF
+  // CHECK-NEXT: [[T8:%[0-9]+]] = alloc_stack $Never
+  // CHECK-NEXT: try_apply [[T7]]<Never>([[T8]], [[T6]])
+  genericPassThrough(neverThrow)
+}
+
+// CHECK-LABEL: sil{{.*}} @$s18typed_throws_thunk5test4yyyyxYKXEKs5ErrorRzlF
+// Indirect -> Indirect should not require a thunk
+func test4<T: Error>(_ x: () throws(T) -> Void) throws {
+  // CHECK-NOT: function_ref thunk for
+  // CHECK: [[FN:%[0-9]+]] = function_ref @$s18typed_throws_thunk18genericPassThroughyyyyxYKXExYKs5ErrorRzlF
+  // CHECK: try_apply [[FN]]
+  try genericPassThrough(x)
+}
+
+// CHECK-LABEL: sil{{.*}} @$s18typed_throws_thunk5test5yyyyxYKXEKs5ErrorRzlF
+// Indirect -> Existential should require a thunk
+func test5<T: Error>(_ x: () throws(T) -> Void) throws {
+  // CHECK: bb0([[T0:%[0-9]+]]
+  // CHECK:      [[T3:%[0-9]+]] = copy_value [[T0]]
+  // CHECK-NEXT: [[T4:%[0-9]+]] = convert_function [[T3]]
+  // CHECK-NEXT: // function_ref thunk for @callee_guaranteed () -> (@error @out A)
+  // CHECK-NEXT: [[T5:%[0-9]+]] = function_ref @$sxIgzr_s5Error_pIegzo_sAARzlTR
+  // CHECK-NEXT: [[T6:%[0-9]+]] = partial_apply [callee_guaranteed] [[T5]]<T>([[T4]])
+  // CHECK-NEXT: [[T7:%[0-9]+]] = convert_escape_to_noescape [not_guaranteed] [[T6]]
+  // CHECK-NEXT: // function_ref existentialPassThrough(_:)
+  // CHECK-NEXT: [[T8:%[0-9]+]] = function_ref @$s18typed_throws_thunk22existentialPassThroughyyyyKXEKF
+  // CHECK-NEXT: try_apply [[T8]]([[T7]])
+  try existentialPassThrough(x)
+}
+
+// CHECK-LABEL: sil{{.*}} @$s18typed_throws_thunk5test6yyKF
+// Concrete -> Existential should require a thunk
+func test6() throws {
+  // CHECK:      [[T1:%[0-9]+]] = function_ref @$s18typed_throws_thunk13throwConcreteyyAA0E5ErrorVYKF
+  // CHECK-NEXT: [[T2:%[0-9]+]] = thin_to_thick_function [[T1]]
+  // CHECK-NEXT: // function_ref thunk for @escaping @callee_guaranteed () -> (@error @owned ConcreteError)
+  // CHECK-NEXT: [[T3:%[0-9]+]] = function_ref @$s18typed_throws_thunk13ConcreteErrorVIegzo_s0E0_pIegzo_TR
+  // CHECK-NEXT: [[T4:%[0-9]+]] = partial_apply [callee_guaranteed] [[T3]]([[T2]])
+  // CHECK-NEXT: [[T5:%[0-9]+]] = convert_escape_to_noescape [not_guaranteed] [[T4]]
+  // CHECK-NEXT: // function_ref existentialPassThrough(_:)
+  // CHECK-NEXT: [[T6:%[0-9]+]] = function_ref @$s18typed_throws_thunk22existentialPassThroughyyyyKXEKF
+  // CHECK-NEXT: try_apply [[T6]]([[T5]])
+  try existentialPassThrough(throwConcrete)
+}
+
+// CHECK-LABEL: sil{{.*}} @$s18typed_throws_thunk5test7yyKF
+// Concrete -> Concrete should not require a thunk
+func test7() throws {
+  // CHECK-NOT: function_ref thunk for
+  // CHECK: [[FN:%[0-9]+]] = function_ref @$s18typed_throws_thunk19concretePassThroughyyyyAA13ConcreteErrorVYKXEADYKF
+  // CHECK: try_apply [[FN]]
+  try concretePassThrough(throwConcrete)
+}
+
+// CHECK-LABEL: sil{{.*}} @$s18typed_throws_thunk5test8yyKF
+// Concrete -> Indirect should require a thunk
+func test8() throws {
+  // CHECK:      [[T1:%[0-9]+]] = function_ref @$s18typed_throws_thunk13throwConcreteyyAA0E5ErrorVYKF
+  // CHECK-NEXT: [[T2:%[0-9]+]] = thin_to_thick_function [[T1]]
+  // CHECK-NEXT: [[T3:%[0-9]+]] = convert_escape_to_noescape [not_guaranteed] [[T2]]
+  // CHECK-NEXT: // function_ref thunk for @callee_guaranteed () -> (@error @owned ConcreteError)
+  // CHECK-NEXT: [[T4:%[0-9]+]] = function_ref @$s18typed_throws_thunk13ConcreteErrorVIgzo_ACIegzr_TR
+  // CHECK-NEXT: [[T5:%[0-9]+]] = partial_apply [callee_guaranteed] [[T4]]([[T3]])
+  // CHECK-NEXT: [[T6:%[0-9]+]] = convert_function [[T5]]
+  // CHECK-NEXT: [[T7:%[0-9]+]] = convert_escape_to_noescape [not_guaranteed] [[T6]]
+  // CHECK-NEXT: // function_ref genericPassThrough<A>(_:)
+  // CHECK-NEXT: [[T8:%[0-9]+]] = function_ref @$s18typed_throws_thunk18genericPassThroughyyyyxYKXExYKs5ErrorRzlF
+  // CHECK-NEXT: [[T9:%[0-9]+]] = alloc_stack $ConcreteError
+  // CHECK-NEXT: try_apply [[T8]]<ConcreteError>([[T9]], [[T7]])
+  try genericPassThrough(throwConcrete)
+}
+
+// CHECK-LABEL: sil{{.*}} @$s18typed_throws_thunk5test9yyKF
+// Existential -> Indirect should require a thunk
+func test9() throws {
+  // CHECK:      [[T1:%[0-9]+]] = function_ref @$s18typed_throws_thunk16throwExistentialyyKF
+  // CHECK-NEXT: [[T2:%[0-9]+]] = thin_to_thick_function [[T1]]
+  // CHECK-NEXT: [[T3:%[0-9]+]] = convert_escape_to_noescape [not_guaranteed] [[T2]]
+  // CHECK-NEXT: // function_ref thunk for @callee_guaranteed () -> (@error @owned Error)
+  // CHECK-NEXT: [[T4:%[0-9]+]] = function_ref @$ss5Error_pIgzo_sAA_pIegzr_TR
+  // CHECK-NEXT: [[T5:%[0-9]+]] = partial_apply [callee_guaranteed] [[T4]]([[T3]])
+  // CHECK-NEXT: [[T6:%[0-9]+]] = convert_function [[T5]]
+  // CHECK-NEXT: [[T7:%[0-9]+]] = convert_escape_to_noescape [not_guaranteed] [[T6]]
+  // CHECK-NEXT: // function_ref genericPassThrough<A>(_:)
+  // CHECK-NEXT: [[T8:%[0-9]+]] = function_ref @$s18typed_throws_thunk18genericPassThroughyyyyxYKXExYKs5ErrorRzlF
+  // CHECK-NEXT: [[T9:%[0-9]+]] = alloc_stack $any Error
+  // CHECK-NEXT: try_apply [[T8]]<any Error>([[T9]], [[T7]])
+  try genericPassThrough(throwExistential)
+}