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[SILGen] Create thunks for non-throwing -> indirect error result conversions
When a non-throwing function is passed to a function that expects a throwing function with an indirect error result, we need to create a thunk because the indirect error result pointer is passed as an extra trailing parameter. Extra trailing parameters except for `swifterror` and `swiftself` are not allowed on some platforms like WebAssembly, so they need to be called as exactly the same function signature. ```swift func passThrough<X>(_ c: () throws(X) -> Void) throws(X) { try c() } func neverThrow() {} passThrough(neverThrow) ```
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‎lib/SIL/IR/TypeLowering.cpp

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

‎test/SILGen/typed_throws_thunk.swift

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

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