mirror of https://github.com/boa-dev/boa.git
Browse Source
* Implement register allocation * Apply review * Update core/engine/src/vm/opcode/rest_parameter/mod.rs Co-authored-by: raskad <32105367+raskad@users.noreply.github.com> --------- Co-authored-by: raskad <32105367+raskad@users.noreply.github.com>pull/3997/head
Haled Odat
3 months ago
committed by
GitHub
16 changed files with 338 additions and 44 deletions
@ -0,0 +1,140 @@
|
||||
use std::mem::forget; |
||||
|
||||
bitflags::bitflags! { |
||||
#[derive(Debug, Default, Clone, Copy)] |
||||
struct RegisterFlags: u8 { |
||||
/// Whether the register is still in use (not deallocated).
|
||||
const USED = 0b0000_0001; |
||||
|
||||
/// Is the register presistent (not deallocatable).
|
||||
const PERSISTENT = 0b0000_0010; |
||||
} |
||||
} |
||||
|
||||
impl RegisterFlags { |
||||
fn is_used(self) -> bool { |
||||
self.contains(Self::USED) |
||||
} |
||||
fn is_persistent(self) -> bool { |
||||
self.contains(Self::PERSISTENT) |
||||
} |
||||
} |
||||
|
||||
/// An entry in the [`RegisterAllocator`].
|
||||
#[derive(Debug, Default)] |
||||
pub(crate) struct RegisterEntry { |
||||
flags: RegisterFlags, |
||||
} |
||||
|
||||
/// Represent a VM register.
|
||||
///
|
||||
/// This is intented to be passed by reference or to be moved, dropping this is a bug,
|
||||
/// it should only be dropped though the [`RegisterAllocator::dealloc()`] method.
|
||||
/// This doesn't apply to persistent registers.
|
||||
///
|
||||
/// A [`Register`] is index into the register allocator,
|
||||
/// as well as an index into the registers on the stack using the register pointer (`rp`).
|
||||
#[derive(Debug)] |
||||
pub(crate) struct Register { |
||||
index: u32, |
||||
flags: RegisterFlags, |
||||
} |
||||
|
||||
impl Register { |
||||
/// The index of the [`Register`].
|
||||
pub(crate) fn index(&self) -> u32 { |
||||
self.index |
||||
} |
||||
} |
||||
|
||||
impl Drop for Register { |
||||
/// This method should never be called.
|
||||
/// It is used to detect when a register has not been deallocated.
|
||||
fn drop(&mut self) { |
||||
if self.flags.is_persistent() { |
||||
return; |
||||
} |
||||
|
||||
// Prevent double panic.
|
||||
if std::thread::panicking() { |
||||
return; |
||||
} |
||||
|
||||
unreachable!("forgot to deallocate a register!") |
||||
} |
||||
} |
||||
|
||||
#[derive(Debug, Default)] |
||||
pub(crate) struct RegisterAllocator { |
||||
registers: Vec<RegisterEntry>, |
||||
} |
||||
|
||||
impl RegisterAllocator { |
||||
pub(crate) fn alloc(&mut self) -> Register { |
||||
if let Some((i, register)) = self |
||||
.registers |
||||
.iter_mut() |
||||
.filter(|reg| !reg.flags.is_used()) |
||||
.enumerate() |
||||
.next() |
||||
{ |
||||
assert!(!register.flags.is_persistent()); |
||||
|
||||
register.flags |= RegisterFlags::USED; |
||||
return Register { |
||||
index: i as u32, |
||||
flags: register.flags, |
||||
}; |
||||
} |
||||
|
||||
let flags = RegisterFlags::USED; |
||||
|
||||
let index = self.registers.len() as u32; |
||||
self.registers.push(RegisterEntry { flags }); |
||||
|
||||
Register { index, flags } |
||||
} |
||||
|
||||
pub(crate) fn alloc_persistent(&mut self) -> Register { |
||||
let mut reg = self.alloc(); |
||||
|
||||
let index = reg.index(); |
||||
|
||||
let register = &mut self.registers[index as usize]; |
||||
|
||||
register.flags |= RegisterFlags::PERSISTENT; |
||||
|
||||
reg.flags = register.flags; |
||||
reg |
||||
} |
||||
|
||||
#[allow(unused)] |
||||
pub(crate) fn dealloc(&mut self, reg: Register) { |
||||
assert!( |
||||
!reg.flags.is_persistent(), |
||||
"Trying to deallocate a persistent register" |
||||
); |
||||
|
||||
let register = &mut self.registers[reg.index as usize]; |
||||
|
||||
assert!( |
||||
register.flags.is_used(), |
||||
"Cannot deallocate unused variable" |
||||
); |
||||
register.flags.set(RegisterFlags::USED, false); |
||||
|
||||
// NOTE: We should not drop it since, dropping it used to detect bugs.
|
||||
forget(reg); |
||||
} |
||||
|
||||
pub(crate) fn finish(self) -> u32 { |
||||
for register in &self.registers { |
||||
debug_assert!( |
||||
!register.flags.is_used() |
||||
|| (register.flags.is_used() && register.flags.is_persistent()) |
||||
); |
||||
} |
||||
|
||||
self.registers.len() as u32 |
||||
} |
||||
} |
||||
Loading…
Reference in new issue