ObjClass* wrenGetClass(WrenVM* vm, Value value)
{
return wrenGetClassInline(vm, value);
}
// The main bytecode interpreter loop. This is where the magic happens. It is
// also, as you can imagine, highly performance critical. Returns `true` if the
// fiber completed without error.
static bool runInterpreter(WrenVM* vm)
{
// Hoist these into local variables. They are accessed frequently in the loop
// but assigned less frequently. Keeping them in locals and updating them when
// a call frame has been pushed or popped gives a large speed boost.
register ObjFiber* fiber = vm->fiber;
register CallFrame* frame;
register Value* stackStart;
register uint8_t* ip;
register ObjFn* fn;
// These macros are designed to only be invoked within this function.
#define PUSH(value) (*fiber->stackTop++ = value)
#define POP() (*(--fiber->stackTop))
#define DROP() (fiber->stackTop--)
#define PEEK() (*(fiber->stackTop - 1))
#define PEEK2() (*(fiber->stackTop - 2))
#define READ_BYTE() (*ip++)
#define READ_SHORT() (ip += 2, (ip[-2] << 8) | ip[-1])
// Use this before a CallFrame is pushed to store the local variables back
// into the current one.
#define STORE_FRAME() frame->ip = ip
// Use this after a CallFrame has been pushed or popped to refresh the local
// variables.
#define LOAD_FRAME() \
frame = &fiber->frames[fiber->numFrames - 1]; \
stackStart = frame->stackStart; \
ip = frame->ip; \
if (frame->fn->type == OBJ_FN) \
{ \
fn = (ObjFn*)frame->fn; \
} \
else \
{ \
fn = ((ObjClosure*)frame->fn)->fn; \
}
// Terminates the current fiber with error string [error]. If another calling
// fiber is willing to catch the error, transfers control to it, otherwise
// exits the interpreter.
#define RUNTIME_ERROR(error) \
do { \
STORE_FRAME(); \
fiber = runtimeError(vm, fiber, error); \
if (fiber == NULL) return false; \
LOAD_FRAME(); \
DISPATCH(); \
} \
while (false)
#if WREN_COMPUTED_GOTO
// Note that the order of instructions here must exacly match the Code enum
// in wren_vm.h or horrendously bad things happen.
static void* dispatchTable[] = {
&&code_CONSTANT,
&&code_NULL,
&&code_FALSE,
&&code_TRUE,
&&code_LOAD_LOCAL_0,
&&code_LOAD_LOCAL_1,
&&code_LOAD_LOCAL_2,
&&code_LOAD_LOCAL_3,
&&code_LOAD_LOCAL_4,
&&code_LOAD_LOCAL_5,
&&code_LOAD_LOCAL_6,
&&code_LOAD_LOCAL_7,
&&code_LOAD_LOCAL_8,
&&code_LOAD_LOCAL,
&&code_STORE_LOCAL,
&&code_LOAD_UPVALUE,
&&code_STORE_UPVALUE,
&&code_LOAD_GLOBAL,
&&code_STORE_GLOBAL,
&&code_LOAD_FIELD_THIS,
&&code_STORE_FIELD_THIS,
&&code_LOAD_FIELD,
&&code_STORE_FIELD,
&&code_POP,
&&code_CALL_0,
&&code_CALL_1,
&&code_CALL_2,
&&code_CALL_3,
&&code_CALL_4,
&&code_CALL_5,
&&code_CALL_6,
&&code_CALL_7,
&&code_CALL_8,
&&code_CALL_9,
&&code_CALL_10,
&&code_CALL_11,
&&code_CALL_12,
&&code_CALL_13,
&&code_CALL_14,
&&code_CALL_15,
&&code_CALL_16,
&&code_SUPER_0,
&&code_SUPER_1,
&&code_SUPER_2,
&&code_SUPER_3,
&&code_SUPER_4,
&&code_SUPER_5,
&&code_SUPER_6,
&&code_SUPER_7,
&&code_SUPER_8,
&&code_SUPER_9,
&&code_SUPER_10,
&&code_SUPER_11,
&&code_SUPER_12,
&&code_SUPER_13,
&&code_SUPER_14,
&&code_SUPER_15,
&&code_SUPER_16,
&&code_JUMP,
&&code_LOOP,
&&code_JUMP_IF,
&&code_AND,
&&code_OR,
&&code_IS,
&&code_CLOSE_UPVALUE,
&&code_RETURN,
&&code_LIST,
&&code_CLOSURE,
&&code_CLASS,
&&code_METHOD_INSTANCE,
&&code_METHOD_STATIC,
&&code_END
};
#define INTERPRET_LOOP DISPATCH();
#define CASE_CODE(name) code_##name
#if WREN_DEBUG_TRACE_INSTRUCTIONS
// Prints the stack and instruction before each instruction is executed.
#define DISPATCH() \
{ \
wrenDebugPrintStack(fiber); \
wrenDebugPrintInstruction(vm, fn, (int)(ip - fn->bytecode)); \
instruction = *ip++; \
goto *dispatchTable[instruction]; \
}
#else
#define DISPATCH() goto *dispatchTable[instruction = READ_BYTE()];
#endif
#else
#define INTERPRET_LOOP for (;;) switch (instruction = READ_BYTE())
#define CASE_CODE(name) case CODE_##name
#define DISPATCH() break
#endif
LOAD_FRAME();
Code instruction;
INTERPRET_LOOP
{
CASE_CODE(LOAD_LOCAL_0):
CASE_CODE(LOAD_LOCAL_1):
CASE_CODE(LOAD_LOCAL_2):
CASE_CODE(LOAD_LOCAL_3):
CASE_CODE(LOAD_LOCAL_4):
CASE_CODE(LOAD_LOCAL_5):
CASE_CODE(LOAD_LOCAL_6):
CASE_CODE(LOAD_LOCAL_7):
CASE_CODE(LOAD_LOCAL_8):
PUSH(stackStart[instruction - CODE_LOAD_LOCAL_0]);
DISPATCH();
CASE_CODE(LOAD_LOCAL):
PUSH(stackStart[READ_BYTE()]);
DISPATCH();
CASE_CODE(LOAD_FIELD_THIS):
{
int field = READ_BYTE();
Value receiver = stackStart[0];
ASSERT(IS_INSTANCE(receiver), "Receiver should be instance.");
ObjInstance* instance = AS_INSTANCE(receiver);
ASSERT(field < instance->obj.classObj->numFields, "Out of bounds field.");
PUSH(instance->fields[field]);
DISPATCH();
}
CASE_CODE(POP): DROP(); DISPATCH();
CASE_CODE(NULL): PUSH(NULL_VAL); DISPATCH();
CASE_CODE(FALSE): PUSH(FALSE_VAL); DISPATCH();
CASE_CODE(TRUE): PUSH(TRUE_VAL); DISPATCH();
CASE_CODE(CALL_0):
CASE_CODE(CALL_1):
CASE_CODE(CALL_2):
CASE_CODE(CALL_3):
CASE_CODE(CALL_4):
CASE_CODE(CALL_5):
CASE_CODE(CALL_6):
CASE_CODE(CALL_7):
CASE_CODE(CALL_8):
CASE_CODE(CALL_9):
CASE_CODE(CALL_10):
CASE_CODE(CALL_11):
CASE_CODE(CALL_12):
CASE_CODE(CALL_13):
CASE_CODE(CALL_14):
CASE_CODE(CALL_15):
CASE_CODE(CALL_16):
{
// Add one for the implicit receiver argument.
int numArgs = instruction - CODE_CALL_0 + 1;
int symbol = READ_SHORT();
Value receiver = *(fiber->stackTop - numArgs);
ObjClass* classObj = wrenGetClassInline(vm, receiver);
// If the class's method table doesn't include the symbol, bail.
if (symbol >= classObj->methods.count)
{
RUNTIME_ERROR(methodNotFound(vm, classObj, symbol));
}
Method* method = &classObj->methods.data[symbol];
switch (method->type)
{
case METHOD_PRIMITIVE:
{
Value* args = fiber->stackTop - numArgs;
// After calling this, the result will be in the first arg slot.
switch (method->fn.primitive(vm, fiber, args))
{
case PRIM_VALUE:
// The result is now in the first arg slot. Discard the other
// stack slots.
fiber->stackTop -= numArgs - 1;
break;
case PRIM_ERROR:
RUNTIME_ERROR(AS_STRING(args[0]));
case PRIM_CALL:
STORE_FRAME();
callFunction(fiber, AS_OBJ(args[0]), numArgs);
LOAD_FRAME();
break;
case PRIM_RUN_FIBER:
STORE_FRAME();
fiber = AS_FIBER(args[0]);
LOAD_FRAME();
break;
}
break;
}
case METHOD_FOREIGN:
callForeign(vm, fiber, method->fn.foreign, numArgs);
break;
case METHOD_BLOCK:
STORE_FRAME();
callFunction(fiber, method->fn.obj, numArgs);
LOAD_FRAME();
break;
case METHOD_NONE:
RUNTIME_ERROR(methodNotFound(vm, classObj, symbol));
break;
}
DISPATCH();
}
CASE_CODE(STORE_LOCAL):
stackStart[READ_BYTE()] = PEEK();
DISPATCH();
CASE_CODE(CONSTANT):
PUSH(fn->constants[READ_SHORT()]);
DISPATCH();
CASE_CODE(SUPER_0):
CASE_CODE(SUPER_1):
CASE_CODE(SUPER_2):
CASE_CODE(SUPER_3):
CASE_CODE(SUPER_4):
CASE_CODE(SUPER_5):
CASE_CODE(SUPER_6):
CASE_CODE(SUPER_7):
CASE_CODE(SUPER_8):
CASE_CODE(SUPER_9):
CASE_CODE(SUPER_10):
CASE_CODE(SUPER_11):
CASE_CODE(SUPER_12):
CASE_CODE(SUPER_13):
CASE_CODE(SUPER_14):
CASE_CODE(SUPER_15):
CASE_CODE(SUPER_16):
{
// TODO: Almost completely copied from CALL. Unify somehow.
// Add one for the implicit receiver argument.
int numArgs = instruction - CODE_SUPER_0 + 1;
int symbol = READ_SHORT();
Value receiver = *(fiber->stackTop - numArgs);
ObjClass* classObj = wrenGetClassInline(vm, receiver);
// Ignore methods defined on the receiver's immediate class.
classObj = classObj->superclass;
// If the class's method table doesn't include the symbol, bail.
if (symbol >= classObj->methods.count)
{
RUNTIME_ERROR(methodNotFound(vm, classObj, symbol));
}
Method* method = &classObj->methods.data[symbol];
switch (method->type)
{
case METHOD_PRIMITIVE:
{
Value* args = fiber->stackTop - numArgs;
// After calling this, the result will be in the first arg slot.
switch (method->fn.primitive(vm, fiber, args))
{
case PRIM_VALUE:
// The result is now in the first arg slot. Discard the other
// stack slots.
fiber->stackTop -= numArgs - 1;
break;
case PRIM_ERROR:
RUNTIME_ERROR(AS_STRING(args[0]));
case PRIM_CALL:
STORE_FRAME();
callFunction(fiber, AS_OBJ(args[0]), numArgs);
LOAD_FRAME();
break;
case PRIM_RUN_FIBER:
STORE_FRAME();
fiber = AS_FIBER(args[0]);
LOAD_FRAME();
break;
}
break;
}
case METHOD_FOREIGN:
callForeign(vm, fiber, method->fn.foreign, numArgs);
break;
case METHOD_BLOCK:
STORE_FRAME();
callFunction(fiber, method->fn.obj, numArgs);
LOAD_FRAME();
break;
case METHOD_NONE:
RUNTIME_ERROR(methodNotFound(vm, classObj, symbol));
break;
}
DISPATCH();
}
CASE_CODE(LOAD_UPVALUE):
{
Upvalue** upvalues = ((ObjClosure*)frame->fn)->upvalues;
PUSH(*upvalues[READ_BYTE()]->value);
DISPATCH();
}
CASE_CODE(STORE_UPVALUE):
{
Upvalue** upvalues = ((ObjClosure*)frame->fn)->upvalues;
*upvalues[READ_BYTE()]->value = PEEK();
DISPATCH();
}
CASE_CODE(LOAD_GLOBAL):
PUSH(vm->globals.data[READ_SHORT()]);
DISPATCH();
CASE_CODE(STORE_GLOBAL):
vm->globals.data[READ_SHORT()] = PEEK();
DISPATCH();
CASE_CODE(STORE_FIELD_THIS):
{
int field = READ_BYTE();
Value receiver = stackStart[0];
ASSERT(IS_INSTANCE(receiver), "Receiver should be instance.");
ObjInstance* instance = AS_INSTANCE(receiver);
ASSERT(field < instance->obj.classObj->numFields, "Out of bounds field.");
instance->fields[field] = PEEK();
DISPATCH();
}
CASE_CODE(LOAD_FIELD):
{
int field = READ_BYTE();
Value receiver = POP();
ASSERT(IS_INSTANCE(receiver), "Receiver should be instance.");
ObjInstance* instance = AS_INSTANCE(receiver);
ASSERT(field < instance->obj.classObj->numFields, "Out of bounds field.");
PUSH(instance->fields[field]);
DISPATCH();
}
CASE_CODE(STORE_FIELD):
{
int field = READ_BYTE();
Value receiver = POP();
ASSERT(IS_INSTANCE(receiver), "Receiver should be instance.");
ObjInstance* instance = AS_INSTANCE(receiver);
ASSERT(field < instance->obj.classObj->numFields, "Out of bounds field.");
instance->fields[field] = PEEK();
DISPATCH();
}
CASE_CODE(JUMP):
{
int offset = READ_SHORT();
ip += offset;
DISPATCH();
}
CASE_CODE(LOOP):
{
// Jump back to the top of the loop.
int offset = READ_SHORT();
ip -= offset;
DISPATCH();
}
CASE_CODE(JUMP_IF):
{
int offset = READ_SHORT();
Value condition = POP();
if (IS_FALSE(condition) || IS_NULL(condition)) ip += offset;
DISPATCH();
}
CASE_CODE(AND):
{
int offset = READ_SHORT();
Value condition = PEEK();
if (IS_FALSE(condition) || IS_NULL(condition))
{
// Short-circuit the right hand side.
ip += offset;
}
else
{
// Discard the condition and evaluate the right hand side.
DROP();
}
DISPATCH();
}
CASE_CODE(OR):
{
int offset = READ_SHORT();
Value condition = PEEK();
if (IS_FALSE(condition) || IS_NULL(condition))
{
// Discard the condition and evaluate the right hand side.
DROP();
}
else
{
// Short-circuit the right hand side.
ip += offset;
}
DISPATCH();
}
CASE_CODE(IS):
{
Value expected = POP();
if (!IS_CLASS(expected))
{
const char* message = "Right operand must be a class.";
RUNTIME_ERROR(AS_STRING(wrenNewString(vm, message, strlen(message))));
}
ObjClass* actual = wrenGetClass(vm, POP());
bool isInstance = false;
// Walk the superclass chain looking for the class.
while (actual != NULL)
{
if (actual == AS_CLASS(expected))
{
isInstance = true;
break;
}
actual = actual->superclass;
}
PUSH(BOOL_VAL(isInstance));
DISPATCH();
}
CASE_CODE(CLOSE_UPVALUE):
closeUpvalue(fiber);
DROP();
DISPATCH();
CASE_CODE(RETURN):
{
Value result = POP();
fiber->numFrames--;
// Close any upvalues still in scope.
Value* firstValue = stackStart;
while (fiber->openUpvalues != NULL &&
fiber->openUpvalues->value >= firstValue)
{
closeUpvalue(fiber);
}
// If the fiber is complete, end it.
if (fiber->numFrames == 0)
{
// If this is the main fiber, we're done.
if (fiber->caller == NULL) return true;
// We have a calling fiber to resume.
fiber = fiber->caller;
// Store the result in the resuming fiber.
*(fiber->stackTop - 1) = result;
}
else
{
// Store the result of the block in the first slot, which is where the
// caller expects it.
stackStart[0] = result;
// Discard the stack slots for the call frame (leaving one slot for the
// result).
fiber->stackTop = frame->stackStart + 1;
}
LOAD_FRAME();
DISPATCH();
}
CASE_CODE(LIST):
{
int numElements = READ_BYTE();
ObjList* list = wrenNewList(vm, numElements);
// TODO: Do a straight memcopy.
for (int i = 0; i < numElements; i++)
{
list->elements[i] = *(fiber->stackTop - numElements + i);
}
// Discard the elements.
fiber->stackTop -= numElements;
PUSH(OBJ_VAL(list));
DISPATCH();
}
CASE_CODE(CLOSURE):
{
ObjFn* prototype = AS_FN(fn->constants[READ_SHORT()]);
ASSERT(prototype->numUpvalues > 0,
"Should not create closure for functions that don't need it.");
// Create the closure and push it on the stack before creating upvalues
// so that it doesn't get collected.
ObjClosure* closure = wrenNewClosure(vm, prototype);
PUSH(OBJ_VAL(closure));
// Capture upvalues.
for (int i = 0; i < prototype->numUpvalues; i++)
{
bool isLocal = READ_BYTE();
int index = READ_BYTE();
if (isLocal)
{
// Make an new upvalue to close over the parent's local variable.
closure->upvalues[i] = captureUpvalue(vm, fiber,
frame->stackStart + index);
}
else
{
// Use the same upvalue as the current call frame.
closure->upvalues[i] = ((ObjClosure*)frame->fn)->upvalues[index];
}
}
DISPATCH();
}
CASE_CODE(CLASS):
{
ObjString* name = AS_STRING(PEEK2());
ObjClass* superclass;
if (IS_NULL(PEEK()))
{
// Implicit Object superclass.
superclass = vm->objectClass;
}
else
{
// TODO: Handle the superclass not being a class object!
superclass = AS_CLASS(PEEK());
}
int numFields = READ_BYTE();
ObjClass* classObj = wrenNewClass(vm, superclass, numFields, name);
// Don't pop the superclass and name off the stack until the subclass is
// done being created, to make sure it doesn't get collected.
DROP();
DROP();
// Now that we know the total number of fields, make sure we don't
// overflow.
if (superclass->numFields + numFields > MAX_FIELDS)
{
char message[70 + MAX_VARIABLE_NAME];
snprintf(message, 70 + MAX_VARIABLE_NAME,
"Class '%s' may not have more than %d fields, including inherited "
"ones.", name->value, MAX_FIELDS);
RUNTIME_ERROR(AS_STRING(wrenNewString(vm, message, strlen(message))));
}
PUSH(OBJ_VAL(classObj));
DISPATCH();
}
CASE_CODE(METHOD_INSTANCE):
CASE_CODE(METHOD_STATIC):
{
int type = instruction;
int symbol = READ_SHORT();
ObjClass* classObj = AS_CLASS(PEEK());
Value method = PEEK2();
bindMethod(vm, type, symbol, classObj, method);
DROP();
DROP();
DISPATCH();
}
CASE_CODE(END):
// A CODE_END should always be preceded by a CODE_RETURN. If we get here,
// the compiler generated wrong code.
UNREACHABLE();
}
// We should only exit this function from an explicit return from CODE_RETURN
// or a runtime error.
UNREACHABLE();
return false;
}
WrenInterpretResult wrenInterpret(WrenVM* vm, const char* sourcePath,
const char* source)
{
// TODO: Check for freed VM.
ObjFn* fn = wrenCompile(vm, sourcePath, source);
if (fn == NULL) return WREN_RESULT_COMPILE_ERROR;
WREN_PIN(vm, fn);
vm->fiber = wrenNewFiber(vm, (Obj*)fn);
WREN_UNPIN(vm);
if (runInterpreter(vm))
{
return WREN_RESULT_SUCCESS;
}
else
{
return WREN_RESULT_RUNTIME_ERROR;
}
}
