Struct cranelift_codegen::machinst::vcode::VCodeConstants

pub struct VCodeConstants { /* fields omitted */ }

This structure tracks the large constants used in VCode that will be emitted separately by the MachBuffer.

First, during the lowering phase, constants are inserted using [VCodeConstants.insert]; an intermediate handle, VCodeConstant, tracks what constants are used in this phase. Some deduplication is performed, when possible, as constant values are inserted.

Secondly, during the emission phase, the MachBuffer assigns MachLabels for each of the constants so that instructions can refer to the value’s memory location. The MachBuffer then writes the constant values to the buffer.

Implementations

impl VCodeConstants

pub fn with_capacity(expected_num_constants: usize) -> Self

Initialize the structure with the expected number of constants.

pub fn insert(&mut self, data: VCodeConstantData) -> VCodeConstant

Insert a constant; using this method indicates that a constant value will be used and thus will be emitted to the MachBuffer. The current implementation can deduplicate constants that are VCodeConstantData::Pool or VCodeConstantData::WellKnown but not VCodeConstantData::Generated.

pub fn get(&self, constant: VCodeConstant) -> Option<&[u8]>

Retrieve a byte slice for the given VCodeConstant, if available.

pub fn len(&self) -> usize

Return the number of constants inserted.

pub fn keys(&self) -> Keys<VCodeConstant>

Iterate over the VCodeConstant keys inserted in this structure.

pub fn iter(&self) -> impl Iterator<Item = (VCodeConstant, &VCodeConstantData)>

Iterate over the VCodeConstant keys and the data (as a byte slice) inserted in this structure.

Trait Implementations

impl Default for VCodeConstants

fn default() -> VCodeConstants

Returns the “default value” for a type.