compiler: fix expanded structs in invoke calls

compiler/compiler.go

@@ -419,17 +419,9 @@ func (c *Compiler) Compile(mainPath string) error {
 			if f.LLVMFn.IsNil() {
 				return errors.New("cannot find function: " + f.LinkName())
 			}
-			fn := f.LLVMFn
-			receiverType := fn.Type().ElementType().ParamTypes()[0]
-			if c.targetData.TypeAllocSize(receiverType) > c.targetData.TypeAllocSize(c.i8ptrType) {
-				// The receiver value doesn't fit in a pointer. This means that
-				// the interface contains a pointer to the receiver value
-				// instead of the value itself. Which means we have to create a
-				// wrapper function.
-				fn, err = c.wrapInterfaceInvoke(f)
-				if err != nil {
-					return err
-				}
+			fn, err := c.wrapInterfaceInvoke(f)
+			if err != nil {
+				return err
 			}
 			fnPtr := llvm.ConstBitCast(fn, c.i8ptrType)
 			funcPointers = append(funcPointers, fnPtr)
@@ -771,12 +763,25 @@ func (c *Compiler) getDIType(typ types.Type) (llvm.Metadata, error) {
 // wrapper is only needed when the interface value actually doesn't fit in a
 // pointer and a pointer to the value must be created.
 func (c *Compiler) wrapInterfaceInvoke(f *ir.Function) (llvm.Value, error) {
+	receiverType, err := c.getLLVMType(f.Params[0].Type())
+	if err != nil {
+		return llvm.Value{}, err
+	}
+	expandedReceiverType := c.expandFormalParamType(receiverType)
+
+	if c.targetData.TypeAllocSize(receiverType) <= c.targetData.TypeAllocSize(c.i8ptrType) && len(expandedReceiverType) == 1 {
+		// nothing to wrap
+		return f.LLVMFn, nil
+	}
+
+	// create wrapper function
 	fnType := f.LLVMFn.Type().ElementType()
-	paramTypes := append([]llvm.Type{c.i8ptrType}, fnType.ParamTypes()[1:]...)
+	paramTypes := append([]llvm.Type{c.i8ptrType}, fnType.ParamTypes()[len(expandedReceiverType):]...)
 	wrapFnType := llvm.FunctionType(fnType.ReturnType(), paramTypes, false)
 	wrapper := llvm.AddFunction(c.mod, f.LinkName()+"$invoke", wrapFnType)
 	wrapper.SetLinkage(llvm.InternalLinkage)
 
+	// add debug info
 	pos := c.ir.Program.Fset.Position(f.Pos())
 	difunc, err := c.attachDebugInfoRaw(f, wrapper, "$invoke", pos.Filename, pos.Line)
 	if err != nil {
@@ -784,13 +789,35 @@ func (c *Compiler) wrapInterfaceInvoke(f *ir.Function) (llvm.Value, error) {
 	}
 	c.builder.SetCurrentDebugLocation(uint(pos.Line), uint(pos.Column), difunc, llvm.Metadata{})
 
+	// set up IR builder
 	block := c.ctx.AddBasicBlock(wrapper, "entry")
 	c.builder.SetInsertPointAtEnd(block)
-	receiverType := fnType.ParamTypes()[0]
-	receiverPtrType := llvm.PointerType(receiverType, 0)
-	receiverPtr := c.builder.CreateBitCast(wrapper.Param(0), receiverPtrType, "receiver.ptr")
-	receiver := c.builder.CreateLoad(receiverPtr, "receiver")
-	params := append([]llvm.Value{receiver}, wrapper.Params()[1:]...)
+
+	var receiverPtr llvm.Value
+	if c.targetData.TypeAllocSize(receiverType) > c.targetData.TypeAllocSize(c.i8ptrType) {
+		// The receiver is passed in using a pointer. We have to load it here
+		// and pass it by value to the real function.
+
+		// Load the underlying value.
+		receiverPtrType := llvm.PointerType(receiverType, 0)
+		receiverPtr = c.builder.CreateBitCast(wrapper.Param(0), receiverPtrType, "receiver.ptr")
+	} else if len(expandedReceiverType) != 1 {
+		// The value is stored in the interface, but it is of type struct which
+		// is expanded to multiple parameters (e.g. {i8, i8}). So we have to
+		// receive the struct as parameter, expand it, and pass it on to the
+		// real function.
+
+		// Cast the passed-in i8* to the struct value (using an alloca) and
+		// extract its values.
+		alloca := c.builder.CreateAlloca(c.i8ptrType, "receiver.alloca")
+		c.builder.CreateStore(wrapper.Param(0), alloca)
+		receiverPtr = c.builder.CreateBitCast(alloca, llvm.PointerType(receiverType, 0), "receiver.ptr")
+	} else {
+		panic("unreachable")
+	}
+
+	receiverValue := c.builder.CreateLoad(receiverPtr, "receiver")
+	params := append(c.expandFormalParam(receiverValue), wrapper.Params()[1:]...)
 	if fnType.ReturnType().TypeKind() == llvm.VoidTypeKind {
 		c.builder.CreateCall(f.LLVMFn, params, "")
 		c.builder.CreateRetVoid()