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//! `CallFrame`
//!
//! This module will provides everything needed to implement the `CallFrame`
use crate::{
builtins::{
iterable::IteratorRecord,
promise::{PromiseCapability, ResolvingFunctions},
},
environments::{BindingLocator, EnvironmentStack},
object::{JsFunction, JsObject},
realm::Realm,
vm::CodeBlock,
JsValue,
};
use boa_gc::{Finalize, Gc, Trace};
use thin_vec::ThinVec;
use super::{ActiveRunnable, Vm};
bitflags::bitflags! {
/// Flags associated with a [`CallFrame`].
#[derive(Debug, Default, Clone, Copy)]
pub(crate) struct CallFrameFlags: u8 {
/// When we return from this [`CallFrame`] to stop execution and
/// return from [`crate::Context::run()`], and leave the remaining [`CallFrame`]s unchanged.
const EXIT_EARLY = 0b0000_0001;
/// Was this [`CallFrame`] created from the `__construct__()` internal object method?
const CONSTRUCT = 0b0000_0010;
/// Does this [`CallFrame`] need to push registers on [`Vm::push_frame()`].
const REGISTERS_ALREADY_PUSHED = 0b0000_0100;
}
}
/// A `CallFrame` holds the state of a function call.
#[derive(Clone, Debug, Finalize, Trace)]
pub struct CallFrame {
pub(crate) code_block: Gc<CodeBlock>,
pub(crate) pc: u32,
/// The register pointer, points to the first register in the stack.
// TODO: Check if storing the frame pointer instead of argument count and computing the
// argument count based on the pointers would be better for accessing the arguments
// and the elements before the register pointer.
pub(crate) rp: u32,
pub(crate) argument_count: u32,
pub(crate) env_fp: u32,
// Iterators and their `[[Done]]` flags that must be closed when an abrupt completion is thrown.
pub(crate) iterators: ThinVec<IteratorRecord>,
// The stack of bindings being updated.
pub(crate) binding_stack: Vec<BindingLocator>,
/// How many iterations a loop has done.
pub(crate) loop_iteration_count: u64,
/// \[\[ScriptOrModule\]\]
pub(crate) active_runnable: Option<ActiveRunnable>,
/// \[\[Environment\]\]
pub(crate) environments: EnvironmentStack,
/// \[\[Realm\]\]
pub(crate) realm: Realm,
// SAFETY: Nothing in `CallFrameFlags` requires tracing, so this is safe.
#[unsafe_ignore_trace]
pub(crate) flags: CallFrameFlags,
}
/// ---- `CallFrame` public API ----
impl CallFrame {
/// Retrieves the [`CodeBlock`] of this call frame.
#[inline]
#[must_use]
pub const fn code_block(&self) -> &Gc<CodeBlock> {
&self.code_block
}
}
/// ---- `CallFrame` creation methods ----
impl CallFrame {
/// This is the size of the function prologue.
///
/// The position of the elements are relative to the [`CallFrame::fp`] (register pointer).
///
/// ```text
/// Setup by the caller
/// ┌─────────────────────────────────────────────────────────┐ ┌───── register pointer
/// ▼ ▼ ▼
/// | -(2 + N): this | -(1 + N): func | -N: arg1 | ... | -1: argN | 0: local1 | ... | K: localK |
/// ▲ ▲ ▲ ▲ ▲ ▲
/// └──────────────────────────────┘ └──────────────────────┘ └─────────────────────────┘
/// function prologue arguments Setup by the callee
/// ▲
/// └─ Frame pointer
/// ```
///
/// ### Example
///
/// The following function calls, generate the following stack:
///
/// ```JavaScript
/// function x(a) {
/// }
/// function y(b, c) {
/// return x(b + c)
/// }
///
/// y(1, 2)
/// ```
///
/// ```text
/// caller prologue caller arguments callee prologue callee arguments
/// ┌─────────────────┐ ┌─────────┐ ┌─────────────────┐ ┌──────┐
/// ▼ ▼ ▼ ▼ │ ▼ ▼ ▼
/// | 0: undefined | 1: y | 2: 1 | 3: 2 | 4: undefined | 5: x | 6: 3 |
/// ▲ ▲ ▲
/// │ caller register pointer ────┤ │
/// │ │ callee register pointer
/// │ callee frame pointer
/// │
/// └───── caller frame pointer
/// ```
///
/// Some questions:
///
/// - Who is responsible for cleaning up the stack after a call? The rust caller.
pub(crate) const FUNCTION_PROLOGUE: u32 = 2;
pub(crate) const THIS_POSITION: u32 = 2;
pub(crate) const FUNCTION_POSITION: u32 = 1;
pub(crate) const PROMISE_CAPABILITY_PROMISE_REGISTER_INDEX: u32 = 0;
pub(crate) const PROMISE_CAPABILITY_RESOLVE_REGISTER_INDEX: u32 = 1;
pub(crate) const PROMISE_CAPABILITY_REJECT_REGISTER_INDEX: u32 = 2;
pub(crate) const ASYNC_GENERATOR_OBJECT_REGISTER_INDEX: u32 = 3;
/// Creates a new `CallFrame` with the provided `CodeBlock`.
pub(crate) fn new(
code_block: Gc<CodeBlock>,
active_runnable: Option<ActiveRunnable>,
environments: EnvironmentStack,
realm: Realm,
) -> Self {
Self {
code_block,
pc: 0,
rp: 0,
env_fp: 0,
argument_count: 0,
iterators: ThinVec::new(),
binding_stack: Vec::new(),
loop_iteration_count: 0,
active_runnable,
environments,
realm,
flags: CallFrameFlags::empty(),
}
}
/// Updates a `CallFrame`'s `argument_count` field with the value provided.
pub(crate) fn with_argument_count(mut self, count: u32) -> Self {
self.argument_count = count;
self
}
/// Updates a `CallFrame`'s `env_fp` field with the value provided.
pub(crate) fn with_env_fp(mut self, env_fp: u32) -> Self {
self.env_fp = env_fp;
self
}
/// Updates a `CallFrame`'s `flags` field with the value provided.
pub(crate) fn with_flags(mut self, flags: CallFrameFlags) -> Self {
self.flags = flags;
self
}
pub(crate) fn this(&self, vm: &Vm) -> JsValue {
let this_index = self.rp - self.argument_count - Self::THIS_POSITION;
vm.stack[this_index as usize].clone()
}
pub(crate) fn function(&self, vm: &Vm) -> Option<JsObject> {
let function_index = self.rp - self.argument_count - Self::FUNCTION_POSITION;
if let Some(object) = vm.stack[function_index as usize].as_object() {
return Some(object.clone());
}
None
}
pub(crate) fn arguments<'stack>(&self, vm: &'stack Vm) -> &'stack [JsValue] {
let rp = self.rp as usize;
let argument_count = self.argument_count as usize;
let arguments_start = rp - argument_count;
&vm.stack[arguments_start..rp]
}
pub(crate) fn argument<'stack>(&self, index: usize, vm: &'stack Vm) -> Option<&'stack JsValue> {
self.arguments(vm).get(index)
}
pub(crate) fn fp(&self) -> u32 {
self.rp - self.argument_count - Self::FUNCTION_PROLOGUE
}
pub(crate) fn restore_stack(&self, vm: &mut Vm) {
let fp = self.fp();
vm.stack.truncate(fp as usize);
}
/// Returns the async generator object, if the function that this [`CallFrame`] is from an async generator, [`None`] otherwise.
pub(crate) fn async_generator_object(&self, stack: &[JsValue]) -> Option<JsObject> {
if !self.code_block().is_async_generator() {
return None;
}
self.register(Self::ASYNC_GENERATOR_OBJECT_REGISTER_INDEX, stack)
.as_object()
.cloned()
}
pub(crate) fn promise_capability(&self, stack: &[JsValue]) -> Option<PromiseCapability> {
if !self.code_block().is_async() {
return None;
}
let promise = self
.register(Self::PROMISE_CAPABILITY_PROMISE_REGISTER_INDEX, stack)
.as_object()
.cloned()?;
let resolve = self
.register(Self::PROMISE_CAPABILITY_RESOLVE_REGISTER_INDEX, stack)
.as_object()
.cloned()
.and_then(JsFunction::from_object)?;
let reject = self
.register(Self::PROMISE_CAPABILITY_REJECT_REGISTER_INDEX, stack)
.as_object()
.cloned()
.and_then(JsFunction::from_object)?;
Some(PromiseCapability {
promise,
functions: ResolvingFunctions { resolve, reject },
})
}
pub(crate) fn set_promise_capability(
&self,
stack: &mut [JsValue],
promise_capability: Option<&PromiseCapability>,
) {
debug_assert!(
self.code_block().is_async(),
"Only async functions have a promise capability"
);
self.set_register(
Self::PROMISE_CAPABILITY_PROMISE_REGISTER_INDEX,
promise_capability
.map(PromiseCapability::promise)
.cloned()
.map_or_else(JsValue::undefined, Into::into),
stack,
);
self.set_register(
Self::PROMISE_CAPABILITY_RESOLVE_REGISTER_INDEX,
promise_capability
.map(PromiseCapability::resolve)
.cloned()
.map_or_else(JsValue::undefined, Into::into),
stack,
);
self.set_register(
Self::PROMISE_CAPABILITY_REJECT_REGISTER_INDEX,
promise_capability
.map(PromiseCapability::reject)
.cloned()
.map_or_else(JsValue::undefined, Into::into),
stack,
);
}
/// Returns the register at the given index.
///
/// # Panics
///
/// If the index is out of bounds.
pub(crate) fn register<'stack>(&self, index: u32, stack: &'stack [JsValue]) -> &'stack JsValue {
debug_assert!(index < self.code_block().register_count);
let at = self.rp + index;
&stack[at as usize]
}
/// Sets the register at the given index.
///
/// # Panics
///
/// If the index is out of bounds.
pub(crate) fn set_register(&self, index: u32, value: JsValue, stack: &mut [JsValue]) {
debug_assert!(index < self.code_block().register_count);
let at = self.rp + index;
stack[at as usize] = value;
}
/// Does this have the [`CallFrameFlags::EXIT_EARLY`] flag.
pub(crate) fn exit_early(&self) -> bool {
self.flags.contains(CallFrameFlags::EXIT_EARLY)
}
/// Set the [`CallFrameFlags::EXIT_EARLY`] flag.
pub(crate) fn set_exit_early(&mut self, early_exit: bool) {
self.flags.set(CallFrameFlags::EXIT_EARLY, early_exit);
}
/// Does this have the [`CallFrameFlags::CONSTRUCT`] flag.
pub(crate) fn construct(&self) -> bool {
self.flags.contains(CallFrameFlags::CONSTRUCT)
}
/// Does this [`CallFrame`] need to push registers on [`Vm::push_frame()`].
pub(crate) fn registers_already_pushed(&self) -> bool {
self.flags
.contains(CallFrameFlags::REGISTERS_ALREADY_PUSHED)
}
}
/// ---- `CallFrame` stack methods ----
impl CallFrame {
pub(crate) fn set_register_pointer(&mut self, pointer: u32) {
self.rp = pointer;
}
}
/// Indicates how a generator function that has been called/resumed should return.
#[derive(Copy, Clone, Debug, PartialEq, Eq, Default)]
#[repr(u8)]
#[allow(missing_docs)]
pub enum GeneratorResumeKind {
#[default]
Normal = 0,
Throw,
Return,
}
impl From<GeneratorResumeKind> for JsValue {
fn from(value: GeneratorResumeKind) -> Self {
Self::new(value as u8)
}
}
impl JsValue {
/// Convert value to [`GeneratorResumeKind`].
///
/// # Panics
///
/// If not a integer type or not in the range `1..=2`.
#[track_caller]
pub(crate) fn to_generator_resume_kind(&self) -> GeneratorResumeKind {
if let Self::Integer(value) = self {
match *value {
0 => return GeneratorResumeKind::Normal,
1 => return GeneratorResumeKind::Throw,
2 => return GeneratorResumeKind::Return,
_ => unreachable!("generator kind must be a integer between 1..=2, got {value}"),
}
}
unreachable!("generator kind must be a integer type")
}
}