Struct StackMap

pub struct StackMap<'a> { /* private fields */ }

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.

Implementations

impl<'a> StackMap<'a>

pub fn lookup(pc: u32, section: &'a [u8]) -> Option<StackMap<'a>>

Looks up a stack map for pc within the section provided.

The section should be produced by StackMapSection in the compile::stack_map module. The pc should be relative to the start of the .text section in the final executable.

pub fn iter( section: &'a [u8], ) -> Option<impl Iterator<Item = (u32, StackMap<'a>)> + 'a>

Iterate over the stack maps contained in the given stack map section.

This function takes a section as its first argument which must have been created with StackMapSection builder. This is intended to be the raw ELF_WASMTIME_STACK_MAP section from the compilation artifact.

The yielded offsets are relative to the start of the text section for this map’s code object.

pub fn frame_size(&self) -> u32

Returns the byte size of this stack map’s frame.

pub unsafe fn sp(&self, fp: *mut usize) -> *mut usize

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 live_gc_refs( &self, sp: *mut usize, ) -> impl Iterator<Item = *mut u32> + '_

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 fn offsets(&self) -> impl Iterator<Item = u32> + '_

Returns the offsets that this stack map registers GC references at.