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90 lines
3.3 KiB
Rust
90 lines
3.3 KiB
Rust
//! Pass A：块级可达性。
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//!
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//! 消费 `oxide_cfg::build_cfg` 的 Cfg，从 entry 沿 succs DFS（**遍历含 EdgeKind::Exception 边**，
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//! catch/finally 入口强制可达），不可达块的全部指令标记删除。
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use oxide_cfg::build_cfg;
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use oxide_ir::IRFunction;
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/// 从 entry 可达的指令位图（keep 前置：不可达指令为 false）。
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pub(super) fn pass_a_reachable(f: &IRFunction) -> Vec<bool> {
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let cfg = build_cfg(f);
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let mut reachable = vec![false; cfg.blocks.len()];
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let mut stack = vec![cfg.entry];
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while let Some(b) = stack.pop() {
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if reachable[b] {
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continue;
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}
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reachable[b] = true;
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// succs 三边全遍历：Jump / Fallthrough / Exception（保守，异常入口强制可达）
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for &(succ, _kind) in &cfg.blocks[b].succs {
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stack.push(succ);
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}
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}
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// 块可达 → 展开到指令粒度 keep
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let mut keep = vec![false; f.insts.len()];
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for (b, r) in reachable.iter().enumerate() {
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if *r {
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for i in cfg.blocks[b].inst_range.clone() {
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keep[i] = true;
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}
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}
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}
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keep
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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_bytecode::opcode::OpCode;
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use oxide_ir::inst::Inst;
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use oxide_ir::operand::Operand;
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/// 线性函数全可达：所有指令 keep=true。
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#[test]
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fn linear_all_insts_reachable() {
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let mut f = IRFunction::new();
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f.insts.push(Inst::load_const(Operand::Reg(1), 0));
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f.insts
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.push(Inst::new(OpCode::RETURN, Operand::Reg(1), Operand::None, Operand::None));
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let keep = pass_a_reachable(&f);
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assert!(keep.iter().all(|k| *k), "线性函数全指令可达");
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}
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/// return 后死块不可达：标记 keep=false（return 后紧跟的自指 JMP 块）。
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#[test]
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fn unreachable_block_marked_dead() {
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let mut f = IRFunction::new();
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f.insts
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.push(Inst::new(OpCode::RETURN, Operand::Reg(0), Operand::None, Operand::None)); // 0
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f.insts.push(Inst::jmp(0)); // 1: 死块（L0 目标），自指 JMP
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f.insts
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.push(Inst::new(OpCode::RETURN, Operand::Reg(1), 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 keep = pass_a_reachable(&f);
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assert!(keep[0], "RETURN 指令可达");
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assert!(!keep[1] && !keep[2], "return 后死块不可达");
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}
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/// Exception 边保守：TRY_BEGIN 的 Exception 边使 catch 入口强制可达，
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/// 即使没有正常边指向它。
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#[test]
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fn exception_edge_keeps_catch_entry() {
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let mut f = IRFunction::new();
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f.insts.push(Inst::try_begin(0)); // 0: TRY_BEGIN → catch 入口（label 0 → inst 3）
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f.insts.push(Inst::load_const(Operand::Reg(5), 1)); // 1
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f.insts
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.push(Inst::new(OpCode::TRY_END, Operand::None, Operand::None, Operand::None)); // 2
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f.insts.push(Inst::load_const(Operand::Reg(6), 2)); // 3: catch 入口
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f.insts
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.push(Inst::new(OpCode::RETURN, Operand::Reg(6), Operand::None, Operand::None)); // 4
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f.label_pos = vec![Some(3)];
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f.label_count = 1;
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let keep = pass_a_reachable(&f);
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assert!(keep[3] && keep[4], "catch 入口经 Exception 边强制可达");
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}
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}
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