爱特每羊队
105 lines
4.2 KiB
Rust
105 lines
4.2 KiB
Rust
//! Pass 1：块头识别。
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//!
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//! 块头集合 = `{0}` ∪ label 目标位置 ∪ 跳转目标 ∪ 条件跳转 fallthrough 后继。
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use oxide_bytecode::opcode::OpCode;
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use oxide_ir::operand::Operand;
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use oxide_ir::IRFunction;
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/// 识别块头位置：返回 `heads`，长度 `insts.len()+1`（+1 容纳指向末尾的空尾块）。
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pub(super) fn partition_blocks(f: &IRFunction) -> Vec<bool> {
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let len = f.insts.len();
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let mut heads = vec![false; len + 1];
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heads[0] = true;
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for p in f.label_pos.iter().flatten() {
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heads[*p] = true;
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}
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for (i, inst) in f.insts.iter().enumerate() {
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// label 恒在 b 槽（inst.rs 构造 API 保证，不查 rd/a 槽）。
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if let Operand::Label(l) = inst.b {
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match f.label_pos.get(l as usize).and_then(|p| *p) {
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Some(p) => heads[p] = true,
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None => debug_assert!(false, "unresolved label {l}"),
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}
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}
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// 跳转的 fallthrough 后继是块头：条件跳转否则 cond+then 融块、条件边丢失；
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// 无条件 JMP 同样必须切块头——JMP 不 fallthrough，但其后继位置需成块边界，
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// 否则 JMP 与后续指令融块、块尾判定错、Jump 边丢失（DCE 可达性误删目标块）。
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if matches!(inst.op, OpCode::JMP | OpCode::JMP_IF_TRUE | OpCode::JMP_IF_FALSE | OpCode::JMP_IF_NULLISH) {
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heads[i + 1] = true;
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}
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}
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heads
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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use oxide_ir::inst::Inst;
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/// 线性无跳转函数：仅 entry 为块头，其余位置非块头。
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#[test]
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fn linear_function_only_entry_is_head() {
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let mut f = IRFunction::new();
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f.insts
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.push(Inst::new(OpCode::NOP, Operand::None, Operand::None, Operand::None));
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f.insts
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.push(Inst::new(OpCode::NOP, Operand::None, Operand::None, Operand::None));
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f.insts
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.push(Inst::new(OpCode::RETURN, Operand::None, Operand::None, Operand::None));
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let heads = partition_blocks(&f);
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assert_eq!(heads, vec![true, false, false, false], "仅 inst 0 是块头");
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}
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/// label 目标是块头：`label_pos` 指向的指令位置置 heads。
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#[test]
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fn label_target_is_head() {
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let mut f = IRFunction::new();
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f.insts
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.push(Inst::new(OpCode::NOP, Operand::None, Operand::None, Operand::None)); // 0
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f.insts
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.push(Inst::new(OpCode::NOP, Operand::None, Operand::None, Operand::None)); // 1: label 0 目标
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f.insts
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.push(Inst::new(OpCode::RETURN, Operand::None, Operand::None, Operand::None)); // 2
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f.label_pos = vec![Some(1)];
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f.label_count = 1;
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let heads = partition_blocks(&f);
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assert!(heads[0] && heads[1], "entry 与 label 目标都是块头");
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assert!(!heads[2], "非块头位置保持 false");
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}
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/// 条件跳转的 fallthrough 后继是块头（否则 cond+then 融块、条件边丢失）。
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#[test]
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fn conditional_jump_fallthrough_successor_is_head() {
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let mut f = IRFunction::new();
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f.insts.push(Inst::jmp_if_false(1, 0)); // 0: cond → L0(else)
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f.insts
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.push(Inst::new(OpCode::NOP, Operand::None, Operand::None, Operand::None)); // 1: then
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f.insts
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.push(Inst::new(OpCode::RETURN, Operand::None, Operand::None, Operand::None)); // 2
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f.label_pos = vec![Some(2)];
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f.label_count = 1;
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let heads = partition_blocks(&f);
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assert!(heads[1], "条件跳转 fallthrough 后继是块头");
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}
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/// 无条件 JMP 的后继位置成块头（JMP 不 fallthrough，后续代码需独立成块，修复 Jump 边丢失）。
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#[test]
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fn unconditional_jmp_successor_is_head() {
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let mut f = IRFunction::new();
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f.insts.push(Inst::jmp(0)); // 0: → L0
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f.insts
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.push(Inst::new(OpCode::NOP, Operand::None, Operand::None, Operand::None)); // 1: 独立块头
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f.insts
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.push(Inst::new(OpCode::RETURN, Operand::None, Operand::None, Operand::None)); // 2
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f.label_pos = vec![Some(2)];
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f.label_count = 1;
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let heads = partition_blocks(&f);
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assert!(heads[1], "无条件 JMP 后继位置是块头");
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}
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}
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