Struct PreciseAllocation

#[repr(C)]
pub struct PreciseAllocation {
    pub cell_size: usize,
    pub mark: bool,
    pub index_in_space: u32,
    pub adjusted_alignment: bool,
    pub has_valid_cell: bool,
    pub is_newly_allocated: bool,
}

Precise allocation used for large objects (>= LARGE_CUTOFF). Starlight uses mimalloc that already knows what to do for large allocations. The GC shouldn’t have to think about such things. That’s where PreciseAllocation comes in. We will allocate large objects directly using mi_malloc, and put the PreciseAllocation header just before them. We can detect when a *mut GcPointerBase is a PreciseAllocation because it will have the ATOM_SIZE / 2 bit set.

Fields

cell_size: usize

allocation request size

mark: bool

index_in_space: u32

index in precise_allocations

adjusted_alignment: bool

Is alignment adjusted?

has_valid_cell: bool

Is this even valid allocation?

is_newly_allocated: bool

Implementations

impl PreciseAllocation

pub const ALIGNMENT: usize = 16usize

Alignment of allocation.

pub const HALF_ALIGNMENT: usize = 8usize

Alignment of pointer returned by Self::cell.

pub fn is_precise(raw_ptr: *mut ()) -> bool

Check if raw_ptr is precisely allocated.

pub fn mark_atomic(&self) -> &AtomicBool

pub fn from_cell(ptr: *mut HeapObjectHeader) -> *mut PreciseAllocation

Create PreciseAllocation from pointer

pub fn base_pointer(&self) -> *mut ()

Return base pointer

pub fn cell(&self) -> *mut HeapObjectHeader

Return cell address, it is always aligned to Self::HALF_ALIGNMENT.

pub fn above_lower_bound(&self, raw_ptr: *mut ()) -> bool

Return true if raw_ptr is above lower bound

pub fn below_upper_bound(&self, raw_ptr: *mut ()) -> bool

Return true if raw_ptr below upper bound

pub const fn header_size() -> usize

Returns header size + required alignment to make cell be aligned to 8.

pub fn contains(&self, raw_ptr: *mut ()) -> bool

Does this allocation contains raw_ptr?

pub fn flip(&mut self)

pub fn is_marked(&self) -> bool

pub fn test_and_set_marked(&self) -> bool

pub fn clear_marked(&self)

pub fn sweep(&mut self) -> bool

Finalize cell if this allocation is not marked.

pub fn try_create(size: usize, index_in_space: u32) -> *mut PreciseAllocation

Try to create precise allocation (no way that it will return null for now).

pub fn is_newly_allocated(&self) -> bool

pub fn is_live(&self) -> bool

pub fn cell_size(&self) -> usize

return cell size

pub fn destroy(&mut self)

Destroy this allocation

pub fn is_empty(&self) -> bool