Function push_cold_blocks_to_end

crates/codegen/src/ir.rs:2143–2242

flowgraph.c push_cold_blocks_to_end

(blocks: &mut Vec<Block>)

/// flowgraph.c push_cold_blocks_to_end
fn push_cold_blocks_to_end(blocks: &mut Vec<Block>) {
    if blocks.len() <= 1 {
        return;
    }

    mark_cold(blocks);

    // If a cold block falls through to a warm block, add an explicit jump
    let fixups: Vec<(BlockIdx, BlockIdx)> = iter_blocks(blocks)
        .filter(|(_, block)| {
            block.cold
                && block.next != BlockIdx::NULL
                && !blocks[block.next.idx()].cold
                && block
                    .instructions
                    .last()
                    .map(|ins| !ins.instr.is_scope_exit() && !ins.instr.is_unconditional_jump())
                    .unwrap_or(true)
        })
        .map(|(idx, block)| (idx, block.next))
        .collect();

    for (cold_idx, warm_next) in fixups {
        let jump_block_idx = BlockIdx(blocks.len() as u32);
        let loc = blocks[cold_idx.idx()]
            .instructions
            .last()
            .map(|i| i.location)
            .unwrap_or_default();
        let end_loc = blocks[cold_idx.idx()]
            .instructions
            .last()
            .map(|i| i.end_location)
            .unwrap_or_default();
        let mut jump_block = Block {
            cold: true,
            ..Block::default()
        };
        jump_block.instructions.push(InstructionInfo {
            instr: PseudoInstruction::JumpNoInterrupt {
                delta: Arg::marker(),
            }
            .into(),
            arg: OpArg::new(0),
            target: warm_next,
            location: loc,
            end_location: end_loc,
            except_handler: None,
            lineno_override: None,
            cache_entries: 0,
        });
        jump_block.next = blocks[cold_idx.idx()].next;
        blocks[cold_idx.idx()].next = jump_block_idx;
        blocks.push(jump_block);
    }

    // Extract cold block streaks and append at the end
    let mut cold_head: BlockIdx = BlockIdx::NULL;