[mono][swift-interop] Support for Swift frozen struct lowering in mini-JIT/AOT/interpreter (#102143)

* refactor + bug fixes for swift struct marshalling

* mini struct lowering

* interpreter swift struct lowering

* enable SwiftAbiStress on Mono

Author: matouskozak

src/mono/mono/metadata/marshal.c

@@ -3711,7 +3711,7 @@ mono_marshal_get_native_wrapper (MonoMethod *method, gboolean check_exceptions,
 						swift_error_args++;
 					} else if (param_klass == swift_self) {
 						swift_self_args++;
-					} else if (!m_class_is_blittable (param_klass) || m_class_is_simd_type (param_klass)) {
+					} else if (!type_is_blittable (method->signature->params [i]) || m_class_is_simd_type (param_klass)) {
 						swift_error_args = swift_self_args = 0;
 						mono_error_set_generic_error (emitted_error, "System", "InvalidProgramException", "Passing non-blittable types to a P/Invoke with the Swift calling convention is unsupported.");
 						break;
@@ -6693,7 +6693,8 @@ typedef enum {
 	SWIFT_DOUBLE,
 } SwiftPhysicalLoweringKind;
 
-static int get_swift_lowering_alignment (SwiftPhysicalLoweringKind kind) {
+static int get_swift_lowering_alignment (SwiftPhysicalLoweringKind kind) 
+{
 	switch (kind) {
 	case SWIFT_INT64:
 	case SWIFT_DOUBLE:
@@ -6705,7 +6706,8 @@ static int get_swift_lowering_alignment (SwiftPhysicalLoweringKind kind) {
 	}
 }
 
-static void set_lowering_range(guint8* lowered_bytes, guint32 offset, guint32 size, SwiftPhysicalLoweringKind kind) {
+static void set_lowering_range(guint8* lowered_bytes, guint32 offset, guint32 size, SwiftPhysicalLoweringKind kind) 
+{
 	bool force_opaque = false;
 
 	if (offset != ALIGN_TO(offset, get_swift_lowering_alignment(kind))) {
@@ -6736,7 +6738,8 @@ static void set_lowering_range(guint8* lowered_bytes, guint32 offset, guint32 si
 
 static void record_struct_field_physical_lowering (guint8* lowered_bytes, MonoType* type, guint32 offset);
 
-static void record_inlinearray_struct_physical_lowering (guint8* lowered_bytes, MonoClass* klass, guint32 offset) {
+static void record_inlinearray_struct_physical_lowering (guint8* lowered_bytes, MonoClass* klass, guint32 offset) 
+{
 	// Get the first field and record its physical lowering N times
 	MonoClassField* field = mono_class_get_fields_internal (klass, NULL);
 	MonoType* fieldType = field->type;
@@ -6755,17 +6758,21 @@ static void record_struct_physical_lowering (guint8* lowered_bytes, MonoClass* k
 	// For each field, we need to record the physical lowering of it.
 	gpointer iter = NULL;
 	MonoClassField* field;
+	int type_offset = MONO_ABI_SIZEOF (MonoObject);
 	while ((field = mono_class_get_fields_internal (klass, &iter))) {
 		if (field->type->attrs & FIELD_ATTRIBUTE_STATIC)
 			continue;
 		if (mono_field_is_deleted (field))
 			continue;
 
-		record_struct_field_physical_lowering(lowered_bytes, field->type, offset + m_field_get_offset(field));
+		record_struct_field_physical_lowering(lowered_bytes, field->type, (offset + m_field_get_offset(field)) - type_offset);
 	}
 }
 
-static void record_struct_field_physical_lowering (guint8* lowered_bytes, MonoType* type, guint32 offset) {
+static void record_struct_field_physical_lowering (guint8* lowered_bytes, MonoType* type, guint32 offset) 
+{
+	int align;
+
 	// Normalize pointer types to IntPtr and resolve generic classes.
 	// We don't need to care about specific pointer types at this ABI level.
 	if (type->type == MONO_TYPE_PTR || type->type == MONO_TYPE_FNPTR) {
@@ -6793,7 +6800,7 @@ static void record_struct_field_physical_lowering (guint8* lowered_bytes, MonoTy
 			kind = SWIFT_DOUBLE;
 		}
 
-		set_lowering_range(lowered_bytes, offset, mono_type_size(type, NULL), kind);
+		set_lowering_range(lowered_bytes, offset, mono_type_size(type, &align), kind);
 	}
 }
 
@@ -6820,13 +6827,13 @@ mono_marshal_get_swift_physical_lowering (MonoType *type, gboolean native_layout
 	}
 
 	MonoClass *klass = mono_class_from_mono_type_internal (type);
-
+	int vtype_size = mono_class_value_size (klass, NULL);
 	// TODO: We currently don't support vector types, so we can say that the maximum size of a non-by_reference struct
 	// is 4 * PointerSize.
 	// Strictly, this is inaccurate in the case where a struct has a fully-empty 8 bytes of padding using explicit layout,
 	// but that's not possible in the Swift layout algorithm.
 
-	if (m_class_get_instance_size(klass) > 4 * TARGET_SIZEOF_VOID_P) {
+	if (vtype_size > 4 * TARGET_SIZEOF_VOID_P) {
 		lowering.by_reference = TRUE;
 		return lowering;
 	}
@@ -6845,8 +6852,7 @@ mono_marshal_get_swift_physical_lowering (MonoType *type, gboolean native_layout
 	GArray* intervals = g_array_new(FALSE, TRUE, sizeof(struct _SwiftInterval));
 
 	// Now we'll build the intervals from the lowered_bytes array
-	int instance_size = m_class_get_instance_size(klass);
-	for (int i = 0; i < instance_size; ++i) {
+	for (int i = 0; i < vtype_size; ++i) {
         	// Don't create an interval for empty bytes
 		if (lowered_bytes[i] == SWIFT_EMPTY) {
 			continue;
@@ -6874,19 +6880,23 @@ mono_marshal_get_swift_physical_lowering (MonoType *type, gboolean native_layout
 	}
 
 	// Merge opaque intervals that are in the same pointer-sized block
-	for (int i = 0; i < intervals->len - 1; ++i) {
-		struct _SwiftInterval current = g_array_index(intervals, struct _SwiftInterval, i);
-		struct _SwiftInterval next = g_array_index(intervals, struct _SwiftInterval, i + 1);
-
-		if (current.kind == SWIFT_OPAQUE && next.kind == SWIFT_OPAQUE && current.start / TARGET_SIZEOF_VOID_P == next.start / TARGET_SIZEOF_VOID_P) {
-			current.size = next.start + next.size - current.start;
-			g_array_remove_index(intervals, i + 1);
-			i--;
+	for (int i = 0; i < intervals->len; ++i) {
+		struct _SwiftInterval interval = g_array_index(intervals, struct _SwiftInterval, i);
+
+		if (i != 0 && interval.kind == SWIFT_OPAQUE) {
+			// Merge two opaque intervals when the previous interval ends in the same pointer-sized block
+			struct _SwiftInterval prevInterval = g_array_index(intervals, struct _SwiftInterval, i - 1);
+			if (prevInterval.kind == SWIFT_OPAQUE && (prevInterval.start + prevInterval.size) / TARGET_SIZEOF_VOID_P == interval.start / TARGET_SIZEOF_VOID_P) {
+				(g_array_index(intervals, struct _SwiftInterval, i - 1)).size = interval.start + interval.size - prevInterval.start;
+				g_array_remove_index(intervals, i);
+				--i;
+				continue;
+			}
 		}
 	}
 
 	// Now that we have the intervals, we can calculate the lowering
-	MonoTypeEnum lowered_types[4];
+	MonoType *lowered_types[4];
 	guint32 offsets[4];
 	guint32 num_lowered_types = 0;
 
@@ -6904,13 +6914,13 @@ mono_marshal_get_swift_physical_lowering (MonoType *type, gboolean native_layout
 
 		switch (interval.kind) {
 			case SWIFT_INT64:
-				lowered_types[num_lowered_types++] = MONO_TYPE_I8;
+				lowered_types[num_lowered_types++] = m_class_get_byval_arg (mono_defaults.int64_class);
 				break;
 			case SWIFT_FLOAT:
-				lowered_types[num_lowered_types++] = MONO_TYPE_R4;
+				lowered_types[num_lowered_types++] = m_class_get_byval_arg (mono_defaults.single_class);
 				break;
 			case SWIFT_DOUBLE:
-				lowered_types[num_lowered_types++] = MONO_TYPE_R8;
+				lowered_types[num_lowered_types++] = m_class_get_byval_arg (mono_defaults.double_class);
 				break;
 			case SWIFT_OPAQUE:
 			{
@@ -6943,20 +6953,20 @@ mono_marshal_get_swift_physical_lowering (MonoType *type, gboolean native_layout
 
 					offsets[num_lowered_types] = opaque_interval_start;
 
-					if (remaining_interval_size > 8 && (opaque_interval_start % 8 == 0)) {
-						lowered_types[num_lowered_types] = MONO_TYPE_I8;
+					if (remaining_interval_size > 4 && (opaque_interval_start % 8 == 0)) {
+						lowered_types[num_lowered_types] = m_class_get_byval_arg (mono_defaults.int64_class);
 						remaining_interval_size -= 8;
 						opaque_interval_start += 8;
-					} else if (remaining_interval_size > 4 && (opaque_interval_start % 4 == 0)) {
-						lowered_types[num_lowered_types] = MONO_TYPE_I4;
+					} else if (remaining_interval_size > 2 && (opaque_interval_start % 4 == 0)) {
+						lowered_types[num_lowered_types] = m_class_get_byval_arg (mono_defaults.int32_class);
 						remaining_interval_size -= 4;
 						opaque_interval_start += 4;
-					} else if (remaining_interval_size > 2 && (opaque_interval_start % 2 == 0)) {
-						lowered_types[num_lowered_types] = MONO_TYPE_I2;
+					} else if (remaining_interval_size > 1 && (opaque_interval_start % 2 == 0)) {
+						lowered_types[num_lowered_types] = m_class_get_byval_arg (mono_defaults.int16_class);
 						remaining_interval_size -= 2;
 						opaque_interval_start += 2;
 					} else {
-						lowered_types[num_lowered_types] = MONO_TYPE_U1;
+						lowered_types[num_lowered_types] = m_class_get_byval_arg (mono_defaults.byte_class);
 						remaining_interval_size -= 1;
 						opaque_interval_start += 1;
 					}
@@ -6967,7 +6977,7 @@ mono_marshal_get_swift_physical_lowering (MonoType *type, gboolean native_layout
 		}
 	}
 
-	memcpy(lowering.lowered_elements, lowered_types, num_lowered_types * sizeof(MonoTypeEnum));
+	memcpy(lowering.lowered_elements, lowered_types, num_lowered_types * sizeof(MonoType*));
 	memcpy(lowering.offsets, offsets, num_lowered_types * sizeof(guint32));
 	lowering.num_lowered_elements = num_lowered_types;
 	lowering.by_reference = FALSE;

src/mono/mono/metadata/marshal.h

@@ -745,8 +745,8 @@ GENERATE_TRY_GET_CLASS_WITH_CACHE_DECL (swift_error)
 
 typedef struct {
 	gboolean by_reference;
-	int num_lowered_elements;
-	MonoTypeEnum lowered_elements[4];
+	uint32_t num_lowered_elements;
+	MonoType *lowered_elements[4];
 	uint32_t offsets[4];
 } SwiftPhysicalLowering;
 

src/mono/mono/metadata/metadata-internals.h

@@ -1010,6 +1010,7 @@ MonoMethodSignature  *mono_metadata_signature_dup_mempool (MonoMemPool *mp, Mono
 MonoMethodSignature  *mono_metadata_signature_dup_mem_manager (MonoMemoryManager *mem_manager, MonoMethodSignature *sig);
 MonoMethodSignature  *mono_metadata_signature_dup_add_this (MonoImage *image, MonoMethodSignature *sig, MonoClass *klass);
 MonoMethodSignature  *mono_metadata_signature_dup_delegate_invoke_to_target (MonoMethodSignature *sig);
+MonoMethodSignature  *mono_metadata_signature_dup_new_params (MonoMemPool *mp, MonoMethodSignature *sig, uint32_t num_params, MonoType **new_params);
 
 MonoGenericInst *
 mono_get_shared_generic_inst (MonoGenericContainer *container);

src/mono/mono/metadata/metadata.c

@@ -2546,6 +2546,37 @@ mono_metadata_signature_dup_delegate_invoke_to_target (MonoMethodSignature *sig)
 	return res;
 }
 
+/**
+ * mono_metadata_signature_dup_new_params:
+ * @param mp The memory pool to allocate the duplicated signature from.
+ * @param sig The original method signature.
+ * @param num_params The number parameters in the new signature.
+ * @param new_params An array of MonoType pointers representing the new parameters.
+ * 
+ * Duplicate an existing \c MonoMethodSignature but with a new set of parameters.
+ * This is a Mono runtime internal function.
+ * 
+ * @return the new \c MonoMethodSignature structure.
+ */
+MonoMethodSignature*
+mono_metadata_signature_dup_new_params (MonoMemPool *mp, MonoMethodSignature *sig, uint32_t num_params, MonoType **new_params)
+{
+	size_t new_sig_size = MONO_SIZEOF_METHOD_SIGNATURE + num_params * sizeof (MonoType*);
+	if (sig->ret)
+		new_sig_size += mono_sizeof_type (sig->ret);
+	
+	MonoMethodSignature *res = (MonoMethodSignature *)mono_mempool_alloc0 (mp, (unsigned int)new_sig_size);
+	memcpy (res, sig, MONO_SIZEOF_METHOD_SIGNATURE);
+	res->param_count = GUINT32_TO_UINT16 (num_params);
+
+	for (uint16_t i = 0; i < res->param_count; i++) {
+		res->params [i] = new_params [i];
+	}
+	res->ret = sig->ret;
+
+	return res;
+}
+
 /*
  * mono_metadata_signature_size:
  *

src/mono/mono/mini/interp/transform.c

@@ -3320,6 +3320,95 @@ interp_try_devirt (MonoClass *this_klass, MonoMethod *target_method)
 	return NULL;
 }
 
+static MonoMethodSignature*
+interp_emit_swiftcall_struct_lowering (TransformData *td, MonoMethodSignature *csignature)
+{
+	// P/Invoke calls shouldn't contain 'this'
+	g_assert (!csignature->hasthis);
+ 	
+	/*
+	 * Argument reordering here doesn't handle on the fly offset allocation 
+	 * and requires the full var offset allocator pass that is only ran for optimized code
+	 */ 
+	g_assert (td->optimized);
+
+	MonoMethodSignature *new_csignature;
+	// Save the function pointer
+	StackInfo sp_fp = td->sp [-1];
+	--td->sp;
+
+	// Save the old arguments				
+	td->sp -= csignature->param_count;
+	StackInfo *sp_old_params = (StackInfo*) mono_mempool_alloc (td->mempool, sizeof (StackInfo) * csignature->param_count);
+	for (int i = 0; i < csignature->param_count; ++i)
+		sp_old_params [i] = td->sp [i];
+
+	GArray *new_params = g_array_sized_new (FALSE, FALSE, sizeof (MonoType*), csignature->param_count);
+	uint32_t new_param_count = 0;
+	int align;
+	MonoClass *swift_self = mono_class_try_get_swift_self_class ();
+	MonoClass *swift_error = mono_class_try_get_swift_error_class ();
+	/*
+	* Go through the lowered arguments, if the argument is a struct, 
+	* we need to replace it with a sequence of lowered arguments.
+	* Also record the updated parameters for the new signature.
+	*/
+	for (int idx_param = 0; idx_param < csignature->param_count; ++idx_param) {
+		MonoType *ptype = csignature->params [idx_param];
+		MonoClass *klass = mono_class_from_mono_type_internal (ptype);
+		// SwiftSelf and SwiftError are special cases where we need to preserve the class information for the codegen to handle them correctly.
+		if (mono_type_is_struct (ptype) && !(klass == swift_self || klass == swift_error)) {
+			SwiftPhysicalLowering lowered_swift_struct = mono_marshal_get_swift_physical_lowering (ptype, FALSE);
+			if (!lowered_swift_struct.by_reference) {
+				for (uint32_t idx_lowered = 0; idx_lowered < lowered_swift_struct.num_lowered_elements; ++idx_lowered) {
+					int mt_lowered = mono_mint_type (lowered_swift_struct.lowered_elements [idx_lowered]);
+					int lowered_elem_size = mono_type_size (lowered_swift_struct.lowered_elements [idx_lowered], &align); 
+					// Load the lowered elements of the struct
+					interp_add_ins (td, MINT_MOV_SRC_OFF);
+					interp_ins_set_sreg (td->last_ins, sp_old_params [idx_param].var);
+					td->last_ins->data [0] = (guint16) lowered_swift_struct.offsets [idx_lowered];
+					td->last_ins->data [1] = GINT_TO_UINT16 (mt_lowered);
+					td->last_ins->data [2] = GINT_TO_UINT16 (lowered_elem_size);
+					push_mono_type (td, lowered_swift_struct.lowered_elements [idx_lowered], mt_lowered, mono_class_from_mono_type_internal (lowered_swift_struct.lowered_elements [idx_lowered]));
+					interp_ins_set_dreg (td->last_ins, td->sp [-1].var);
+					
+					++new_param_count;
+					g_array_append_val (new_params, lowered_swift_struct.lowered_elements [idx_lowered]);
+				}
+			} else {
+				// For structs that cannot be lowered, we change the argument to byref type
+				ptype = mono_class_get_byref_type (mono_defaults.typed_reference_class);
+				// Load the address of the struct
+				interp_add_ins (td, MINT_LDLOCA_S);
+				interp_ins_set_sreg (td->last_ins, sp_old_params [idx_param].var);
+				push_simple_type (td, STACK_TYPE_I);
+				interp_ins_set_dreg (td->last_ins, td->sp [-1].var);
+
+				++new_param_count;
+				g_array_append_val (new_params, ptype);
+			}
+		} else {
+			// Copy over non-struct arguments
+			memcpy (td->sp, &sp_old_params [idx_param], sizeof (StackInfo));
+			++td->sp;
+
+			++new_param_count;
+			g_array_append_val (new_params, ptype);
+		}
+	}
+	// Restore the function pointer
+	memcpy (td->sp, &sp_fp, sizeof (StackInfo));
+	++td->sp;
+
+	// Create a new dummy signature with the lowered arguments
+	new_csignature = mono_metadata_signature_dup_new_params (td->mempool, csignature, new_param_count, (MonoType**)new_params->data);
+
+	// Deallocate temp array
+	g_array_free (new_params, TRUE);
+
+	return new_csignature;
+}
+
 /* Return FALSE if error, including inline failure */
 static gboolean
 interp_transform_call (TransformData *td, MonoMethod *method, MonoMethod *target_method, MonoGenericContext *generic_context, MonoClass *constrained_class, gboolean readonly, MonoError *error, gboolean check_visibility, gboolean save_last_error, gboolean tailcall)
@@ -3404,6 +3493,16 @@ interp_transform_call (TransformData *td, MonoMethod *method, MonoMethod *target
 		return FALSE;
 	}
 
+#ifdef MONO_ARCH_HAVE_SWIFTCALL
+	/*
+	* We need to modify the signature of the swiftcall calli to account for the lowering of Swift structs.
+	* This is done by replacing struct arguments on stack with a lowered sequence and updating the signature.
+	*/
+	if (csignature->pinvoke && mono_method_signature_has_ext_callconv (csignature, MONO_EXT_CALLCONV_SWIFTCALL)) {
+		csignature = interp_emit_swiftcall_struct_lowering (td, csignature);
+	}
+#endif
+
 	if (check_visibility && target_method && !mono_method_can_access_method (method, target_method))
 		interp_generate_mae_throw (td, method, target_method);