[interop][SwiftToCxx] do not emit direct returns/passes when Swift's value type ABI is not yet supported

Author: hyp

lib/PrintAsClang/PrintClangFunction.cpp

@@ -556,8 +556,10 @@ static std::string encodeTypeInfo(const T &abiTypeInfo,
   return std::move(typeEncodingOS.str());
 }
 
+// Returns false if the given direct type is not yet supported because
+// of its ABI.
 template <class T>
-static void printDirectReturnOrParamCType(
+static bool printDirectReturnOrParamCType(
     const T &abiTypeInfo, Type valueType, const ModuleDecl *emittedModule,
     raw_ostream &os, raw_ostream &cPrologueOS,
     PrimitiveTypeMapping &typeMapping,
@@ -575,20 +577,21 @@ static void printDirectReturnOrParamCType(
 
   unsigned Count = 0;
   clang::CharUnits lastOffset;
-  abiTypeInfo.enumerateRecordMembers(
-      [&](clang::CharUnits offset, clang::CharUnits end, Type t) {
+  if (abiTypeInfo.enumerateRecordMembers([&](clang::CharUnits offset,
+                                             clang::CharUnits end, Type t) {
         lastOffset = offset;
         ++Count;
         addABIRecordToTypeEncoding(typeEncodingOS, offset, end, t, typeMapping);
-      });
+      }))
+    return false;
   assert(Count > 0 && "missing return values");
 
   // FIXME: is this "prettyfying" logic sound for multiple return values?
   if (isKnownCType(valueType, typeMapping) ||
       (Count == 1 && lastOffset.isZero() && !valueType->hasTypeParameter() &&
        valueType->isAnyClassReferenceType())) {
     prettifiedValuePrinter();
-    return;
+    return true;
   }
 
   os << "struct " << typeEncodingOS.str();
@@ -642,6 +645,7 @@ static void printDirectReturnOrParamCType(
   interopContext.runIfStubForDeclNotEmitted(typeEncodingOS.str(), [&]() {
     printStub(cPrologueOS, typeEncodingOS.str());
   });
+  return true;
 }
 
 /// Make adjustments to the Swift parameter name in generated C++, to
@@ -750,18 +754,20 @@ ClangRepresentation DeclAndTypeClangFunctionPrinter::printFunctionSignature(
     if (!directResultType) {
       os << "void";
     } else {
-      printDirectReturnOrParamCType(
-          *directResultType, resultTy, emittedModule, os, cPrologueOS,
-          typeMapping, interopContext, [&]() {
-            OptionalTypeKind retKind;
-            Type objTy;
-            std::tie(objTy, retKind) =
-                DeclAndTypePrinter::getObjectTypeAndOptionality(FD, resultTy);
-
-            auto s = printClangFunctionReturnType(objTy, retKind, emittedModule,
-                                                  outputLang);
-            assert(!s.isUnsupported());
-          });
+      if (!printDirectReturnOrParamCType(
+              *directResultType, resultTy, emittedModule, os, cPrologueOS,
+              typeMapping, interopContext, [&]() {
+                OptionalTypeKind retKind;
+                Type objTy;
+                std::tie(objTy, retKind) =
+                    DeclAndTypePrinter::getObjectTypeAndOptionality(FD,
+                                                                    resultTy);
+
+                auto s = printClangFunctionReturnType(
+                    objTy, retKind, emittedModule, outputLang);
+                assert(!s.isUnsupported());
+              }))
+        return ClangRepresentation::unsupported;
     }
   } else {
     OptionalTypeKind retKind;

test/Inputs/clang-importer-sdk/usr/include/simd.h

@@ -39,6 +39,8 @@ typedef double __attribute__((ext_vector_type(3))) double3;
 typedef double __attribute__((ext_vector_type(4))) double4;
 typedef double __attribute__((ext_vector_type(8))) double8;
 
+typedef struct { float4 columns[4]; } float4x4;
+
 // Types that we should not be able to import.
 typedef char __attribute__((ext_vector_type(17))) char17;
 typedef unsigned char __attribute__((ext_vector_type(21))) uchar21;
@@ -89,6 +91,7 @@ ushort6 makes_ushort6();
 int128 makes_int128();
 uint20 makes_uint20();
 
+#ifndef SIMD_NO_CODE
 takes_char2(char2);
 takes_char64(char64);
 takes_uchar3(uchar3);
@@ -130,3 +133,4 @@ takes_short5(short5);
 takes_ushort6(ushort6);
 takes_int128(int128);
 takes_uint20(uint20);
+#endif

test/Interop/CxxToSwiftToCxx/simd-bridge-cxx-struct-back-to-cxx.swift

@@ -0,0 +1,46 @@
+// RUN: %empty-directory(%t)
+// RUN: split-file %s %t
+
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -typecheck %t/use-cxx-types.swift -typecheck -module-name UseCxxTy -emit-clang-header-path %t/UseCxxTy.h -I %t -enable-experimental-cxx-interop -disable-availability-checking -Xcc -DSIMD_NO_CODE
+
+// RUN: %FileCheck %s < %t/UseCxxTy.h
+
+// FIXME: remove once https://github.com/apple/swift/pull/60971 lands.
+// RUN: echo "#include \"header.h\"" > %t/full-cxx-swift-cxx-bridging.h
+// RUN: cat %t/UseCxxTy.h >> %t/full-cxx-swift-cxx-bridging.h
+
+// RUN: %check-interop-cxx-header-in-clang(%t/full-cxx-swift-cxx-bridging.h -Wno-reserved-identifier -DSIMD_NO_CODE)
+
+// This is required to verify that `Struct` is returned and passed directly.
+// REQUIRES: PTRSIZE=64
+
+//--- header.h
+
+#include <simd.h>
+
+using simd_float4x4 = float4x4;
+
+//--- module.modulemap
+module CxxTest {
+    header "header.h"
+    requires cplusplus
+}
+
+//--- use-cxx-types.swift
+import CxxTest
+
+public struct Struct {
+    private let transform: simd_float4x4
+
+    public init() {
+        transform = simd_float4x4()
+    }
+}
+
+public func passStruct(_ x : Struct) {
+    
+}
+
+// CHECK: class SWIFT_SYMBOL("s:8UseCxxTy6StructV") Struct final {
+// CHECK-NOT: init(
+// CHECK:  // Unavailable in C++: Swift global function 'passStruct(_:)'