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Contents
use cranelift_bitset::CompoundBitSet;
use serde_derive::{Deserialize, Serialize};
/// A map for determining where live GC references live in a stack frame.
///
/// Note that this is currently primarily documented as cranelift's
/// `binemit::StackMap`, so for detailed documentation about this please read
/// the docs over there.
#[derive(Debug, Serialize, Deserialize)]
pub struct StackMap {
bits: CompoundBitSet,
frame_size: u32,
}
impl StackMap {
/// Creates a new `StackMap`, typically from a preexisting
/// `binemit::StackMap`.
pub fn new(frame_size: u32, bits: CompoundBitSet) -> StackMap {
StackMap { bits, frame_size }
}
/// Returns the byte size of this stack map's frame.
pub fn frame_size(&self) -> u32 {
self.frame_size
}
/// Given a frame pointer, get the stack pointer.
///
/// # Safety
///
/// The `fp` must be the frame pointer at the code offset that this stack
/// map is associated with.
pub unsafe fn sp(&self, fp: *mut usize) -> *mut usize {
let frame_size = usize::try_from(self.frame_size).unwrap();
fp.byte_sub(frame_size)
}
/// Given the stack pointer, get a reference to each live GC reference in
/// the stack frame.
///
/// # Safety
///
/// The `sp` must be the stack pointer at the code offset that this stack
/// map is associated with.
pub unsafe fn live_gc_refs(&self, sp: *mut usize) -> impl Iterator<Item = *mut u32> + '_ {
self.bits.iter().map(move |i| {
log::trace!("Live GC ref in frame at frame offset {:#x}", i);
let ptr_to_gc_ref = sp.byte_add(i);
// Assert that the pointer is inside this stack map's frame.
assert!({
let delta = ptr_to_gc_ref as usize - sp as usize;
let frame_size = usize::try_from(self.frame_size).unwrap();
delta < frame_size
});
ptr_to_gc_ref.cast::<u32>()
})
}
}
Version data entries
8 entries across 8 versions & 1 rubygems