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[SILGen] Switch @_extern(c) over to a foreign entrypoint #84974

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Merged
merged 2 commits into from
Oct 17, 2025
Merged

[SILGen] Switch @_extern(c) over to a foreign entrypoint #84974

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3445b86
[SILGen] Switch `@_extern(c)` over to a foreign entrypoint
DougGregor Oct 17, 2025
79fc0f1
[extern] Give `@_extern(c)` functions `@convention(c)` type
DougGregor Oct 17, 2025
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3 changes: 3 additions & 0 deletions lib/SIL/IR/SILDeclRef.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -111,6 +111,9 @@ bool swift::requiresForeignEntryPoint(ValueDecl *vd) {
if (vd->hasClangNode())
return true;

if (ExternAttr::find(vd->getAttrs(), ExternKind::C))
return true;

if (auto *accessor = dyn_cast<AccessorDecl>(vd)) {
// Property accessors should be generated alongside the property.
if (accessor->isGetterOrSetter()) {
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2 changes: 0 additions & 2 deletions lib/SIL/IR/SILFunctionType.cpp
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Expand Up @@ -4474,8 +4474,6 @@ TypeConverter::getDeclRefRepresentation(SILDeclRef c) {
case SILDeclRef::Kind::Func:
if (c.getDecl()->getDeclContext()->isTypeContext())
return SILFunctionTypeRepresentation::Method;
if (ExternAttr::find(c.getDecl()->getAttrs(), ExternKind::C))
return SILFunctionTypeRepresentation::CFunctionPointer;
return SILFunctionTypeRepresentation::Thin;

case SILDeclRef::Kind::Destroyer:
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3 changes: 3 additions & 0 deletions lib/SILGen/SILGenExpr.cpp
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Expand Up @@ -996,6 +996,9 @@ emitRValueForDecl(SILLocation loc, ConcreteDeclRef declRef, Type ncRefType,
// If the referenced decl isn't a VarDecl, it should be a constant of some
// sort.
SILDeclRef silDeclRef(decl);
if (ExternAttr::find(decl->getAttrs(), ExternKind::C))
silDeclRef = silDeclRef.asForeign();

assert(silDeclRef.getParameterListCount() == 1);
auto substType = cast<AnyFunctionType>(refType);
auto typeContext = getFunctionTypeInfo(substType);
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5 changes: 5 additions & 0 deletions lib/Sema/TypeCheckDecl.cpp
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Expand Up @@ -2565,6 +2565,11 @@ InterfaceTypeRequest::evaluate(Evaluator &eval, ValueDecl *D) const {
infoBuilder = infoBuilder.withSendingResult();
}

if (ExternAttr::find(D->getAttrs(), ExternKind::C)) {
infoBuilder = infoBuilder.withRepresentation(
FunctionTypeRepresentation::CFunctionPointer);
}

// Lifetime dependencies only apply to the outer function type.
if (!hasSelf && lifetimeDependenceInfo.has_value()) {
infoBuilder =
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28 changes: 20 additions & 8 deletions test/SILGen/extern_c.swift
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Expand Up @@ -6,46 +6,58 @@
@_extern(c, "my_c_name")
func withCName(_ x: Int) -> Int

// CHECK-DAG: sil hidden_external [asmname "take_c_func_ptr"] @$s8extern_c12takeCFuncPtryyS2iXCF : $@convention(c) (@convention(c) (Int) -> Int) -> ()
// CHECK-DAG: sil hidden_external [asmname "take_c_func_ptr"] @$s8extern_c12takeCFuncPtryyS2iXCFTo : $@convention(c) (@convention(c) (Int) -> Int) -> ()
@_extern(c, "take_c_func_ptr")
func takeCFuncPtr(_ f: @convention(c) (Int) -> Int)

// CHECK-DAG: sil [asmname "public_visible"] @$s8extern_c16publicVisibilityyS2iF : $@convention(c) (Int) -> Int
// CHECK-DAG: sil [serialized] [asmname "public_visible"] @$s8extern_c16publicVisibilityyS2iFTo : $@convention(c) (Int) -> Int
@_extern(c, "public_visible")
public func publicVisibility(_ x: Int) -> Int

// CHECK-DAG: sil [asmname "private_visible"] @$s8extern_c17privateVisibility{{.*}} : $@convention(c) (Int) -> Int
@_extern(c, "private_visible")
private func privateVisibility(_ x: Int) -> Int

// CHECK-DAG: sil hidden_external [asmname "withoutCName"] @$s8extern_c12withoutCNameSiyF : $@convention(c) () -> Int
// CHECK-DAG: sil hidden_external [asmname "withoutCName"] @$s8extern_c12withoutCNameSiyFTo : $@convention(c) () -> Int
@_extern(c)
func withoutCName() -> Int

// CHECK-DAG: sil hidden [ossa] @$s8extern_c10defaultArgyySiFfA_ : $@convention(thin) () -> Int {
// CHECK-DAG: sil hidden_external [asmname "default_arg"] @$s8extern_c10defaultArgyySiF : $@convention(c) (Int) -> ()
// CHECK-DAG: sil hidden_external [asmname "default_arg"] @$s8extern_c10defaultArgyySiFTo : $@convention(c) (Int) -> ()
@_extern(c, "default_arg")
func defaultArg(_ x: Int = 42)

func callMe(body: (Int) -> Int) -> Int {
return body(17)
}

func main() {
// CHECK-DAG: [[F1:%.+]] = function_ref @$s8extern_c9withCNameyS2iFTo : $@convention(c) (Int) -> Int
// CHECK-DAG: [[F2:%.+]] = function_ref @$s8extern_c12takeCFuncPtryyS2iXCF : $@convention(c) (@convention(c) (Int) -> Int) -> ()
// CHECK-DAG: [[F2:%.+]] = function_ref @$s8extern_c12takeCFuncPtryyS2iXCFTo : $@convention(c) (@convention(c) (Int) -> Int) -> ()
// CHECK-DAG: apply [[F2]]([[F1]]) : $@convention(c) (@convention(c) (Int) -> Int) -> ()
takeCFuncPtr(withCName)
// CHECK-DAG: [[F3:%.+]] = function_ref @$s8extern_c16publicVisibilityyS2iF : $@convention(c) (Int) -> Int
// CHECK-DAG: [[F3:%.+]] = function_ref @$s8extern_c16publicVisibilityyS2iFTo : $@convention(c) (Int) -> Int
// CHECK-DAG: apply [[F3]]({{.*}}) : $@convention(c) (Int) -> Int
_ = publicVisibility(42)
// CHECK-DAG: [[F4:%.+]] = function_ref @$s8extern_c17privateVisibility{{.*}} : $@convention(c) (Int) -> Int
// CHECK-DAG: apply [[F4]]({{.*}}) : $@convention(c) (Int) -> Int
_ = privateVisibility(24)
// CHECK-DAG: [[F5:%.+]] = function_ref @$s8extern_c12withoutCNameSiyF : $@convention(c) () -> Int
// CHECK-DAG: [[F5:%.+]] = function_ref @$s8extern_c12withoutCNameSiyFTo : $@convention(c) () -> Int
// CHECK-DAG: apply [[F5]]() : $@convention(c) () -> Int
_ = withoutCName()
// CHECK-DAG: [[F6:%.+]] = function_ref @$s8extern_c10defaultArgyySiFfA_ : $@convention(thin) () -> Int
// CHECK-DAG: [[DEFAULT_V:%.+]] = apply [[F6]]() : $@convention(thin) () -> Int
// CHECK-DAG: [[F7:%.+]] = function_ref @$s8extern_c10defaultArgyySiF : $@convention(c) (Int) -> ()
// CHECK-DAG: [[F7:%.+]] = function_ref @$s8extern_c10defaultArgyySiFTo : $@convention(c) (Int) -> ()
// CHECK-DAG: apply [[F7]]([[DEFAULT_V]]) : $@convention(c) (Int) -> ()
defaultArg()

// CHECK-DAG: [[CREF:%[0-9]+]] = function_ref @$s8extern_c16publicVisibilityyS2iFTo : $@convention(c) (Int) -> Int
// CHECK-DAG: [[THUNK:%[0-9]+]] = function_ref @$sS2iIetCyd_S2iIegyd_TR : $@convention(thin) (Int, @convention(c) (Int) -> Int) -> Int
// CHECK-DAG: [[APPLIED:%[0-9]+]] = partial_apply [callee_guaranteed] [[THUNK]]([[CREF]]) : $@convention(thin) (Int, @convention(c) (Int) -> Int) -> Int
// CHECK-DAG: [[NOESCAPE_APPLIED:%[0-9]+]] = convert_escape_to_noescape [not_guaranteed] [[APPLIED]] to $@noescape @callee_guaranteed (Int) -> Int
// CHECK-DAG: [[CALL_ME:%[0-9]+]] = function_ref @$s8extern_c6callMe4bodyS3iXE_tF
// CHECK-DAG: apply [[CALL_ME]]([[NOESCAPE_APPLIED]]) : $@convention(thin) (@guaranteed @noescape @callee_guaranteed (Int) -> Int) -> Int
_ = callMe(body: publicVisibility)
}

main()