Method emit

cranelift/codegen/src/machinst/vcode.rs:736–1174

Emit the instructions to a `MachBuffer`, containing fixed-up code and external reloc/trap/etc. records ready for use. Takes the regalloc results as well. Returns the machine code itself, and optionally metadata and/or a disassembly, as an `EmitResult`. The `VCode` itself is consumed by the emission process.

(
        mut self,
        regalloc: &regalloc2::Output,
        want_disasm: bool,
        flags: &settings::Flags,
        ctrl_plane: &mut ControlPlane,
    )

    /// and/or a disassembly, as an `EmitResult`. The `VCode` itself
    /// is consumed by the emission process.
    pub fn emit(
        mut self,
        regalloc: &regalloc2::Output,
        want_disasm: bool,
        flags: &settings::Flags,
        ctrl_plane: &mut ControlPlane,
    ) -> EmitResult
    where
        I: VCodeInst,
    {
        let _tt = timing::vcode_emit();
        let mut buffer = MachBuffer::new();
        buffer.set_log2_min_function_alignment(self.log2_min_function_alignment);
        let mut bb_starts: Vec<Option<CodeOffset>> = vec![];

        // The first M MachLabels are reserved for block indices.
        buffer.reserve_labels_for_blocks(self.num_blocks());

        // Register all allocated constants with the `MachBuffer` to ensure that
        // any references to the constants during instructions can be handled
        // correctly.
        buffer.register_constants(&self.constants);

        // Construct the final order we emit code in: cold blocks at the end.
        let mut final_order: SmallVec<[BlockIndex; 16]> = smallvec![];
        let mut cold_blocks: SmallVec<[BlockIndex; 16]> = smallvec![];
        for block in 0..self.num_blocks() {
            let block = BlockIndex::new(block);
            if self.block_order.is_cold(block) {
                cold_blocks.push(block);
            } else {
                final_order.push(block);
            }
        }
        final_order.extend(cold_blocks.clone());

        // Compute/save info we need for the prologue: clobbers and
        // number of spillslots.
        //
        // We clone `abi` here because we will mutate it as we
        // generate the prologue and set other info, but we can't
        // mutate `VCode`. The info it usually carries prior to
        // setting clobbers is fairly minimal so this should be
        // relatively cheap.
        let (clobbers, function_calls) = self.compute_clobbers_and_function_calls(regalloc);
        self.abi.compute_frame_layout(
            &self.sigs,
            regalloc.num_spillslots,
            clobbers,
            function_calls,
        );

        // Emit blocks.
        let mut cur_srcloc = None;
        let mut last_offset = None;
        let mut inst_offsets = vec![];
        let mut state = I::State::new(&self.abi, core::mem::take(ctrl_plane));