爱特每羊队
278 lines
11 KiB
Rust
278 lines
11 KiB
Rust
//! CFG 分析 pass：IRFunction → 基本块划分 + 控制流图。
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//!
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//! 消费 `oxide_ir::IRFunction`（只读，不拷贝指令，仅存指令下标区间），产出一次性
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//! 分析快照——pass 输出视图不住进 IR。本 crate 只管 CFG：不建通用分析框架、
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//! 不递归 nested。无生命周期参数——CFG 与 `&IRFunction` 由使用方联合持有访问。
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//!
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//! 构建是四阶段分发：`partition`（块头）→ `split`（切块+出边）→ `exception`
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//! （异常边）→ `finalize`（exit 哨兵 + preds 反推）。每阶段是独立文件的纯函数，
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//! 中间产物（heads / blocks / exit_id）显式传参，无共享可变状态。
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mod exception;
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mod finalize;
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mod partition;
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mod split;
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use oxide_bytecode::opcode::OpCode;
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use oxide_ir::IRFunction;
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/// 基本块 id：blocks 向量下标。
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pub type BBId = usize;
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/// 边三分类：无条件/条件跳转、顺序落入、异常处理入口。
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#[derive(Debug, Clone, Copy, PartialEq, Eq)]
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pub enum EdgeKind {
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Jump,
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Fallthrough,
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Exception,
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}
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/// 基本块：`inst_range` 直接索引 `IRFunction.insts` 切片（不拷贝指令），
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/// preds/succs 双向就位，供 liveness 数据流迭代直接消费。
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#[derive(Debug, Clone, PartialEq, Eq)]
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pub struct BasicBlock {
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pub inst_range: std::ops::Range<usize>,
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pub preds: Vec<BBId>,
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pub succs: Vec<(BBId, EdgeKind)>,
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}
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/// 控制流图快照：实块按指令序编号，exit 哨兵（空块 `0..0`）恒在 blocks 末尾。
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#[derive(Debug, Clone, PartialEq, Eq)]
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pub struct Cfg {
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pub blocks: Vec<BasicBlock>,
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pub entry: BBId,
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pub exit: BBId,
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}
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impl Cfg {
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/// 构造空 CFG：blocks 空、entry/exit 置 0。
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pub fn new() -> Self {
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Self {
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blocks: Vec::new(),
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entry: 0,
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exit: 0,
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}
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}
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}
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impl Default for Cfg {
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fn default() -> Self {
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Self::new()
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}
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}
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/// terminator 判定：块尾指令决定出边。
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///
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/// 注意与 `oxide_ir::lower.rs::is_jump_op` 的差异：lowering 需要为 TRY_BEGIN /
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/// TRY_FINALLY_BEGIN 回填偏移所以把它们并列进 is_jump_op；但 CFG 里它们是**块内
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/// 标记**（异常边起点，见 Pass 3），不是控制流终结——抄用 is_jump_op 会导致 try 体
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/// 被切块、异常边爆炸。
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fn is_terminator(op: OpCode) -> bool {
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matches!(
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op,
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OpCode::JMP
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| OpCode::JMP_IF_TRUE
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| OpCode::JMP_IF_FALSE
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| OpCode::JMP_IF_NULLISH
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| OpCode::RETURN
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| OpCode::HALT
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| OpCode::THROW
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)
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}
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/// 构建 CFG：`&IRFunction → Cfg`。纯函数，只读 IR。
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///
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/// 四阶段分发：`partition::partition_blocks`（Pass 1 块头）→ `split::split_and_edges`
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/// （Pass 2 切块 + 出边）→ `exception::add_exception_edges`（Pass 3 异常边）
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/// → `finalize::finalize`（Pass 4 exit 哨兵 + preds 反推）。幂等：同一 IR 两次构建结果相等。
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pub fn build_cfg(f: &IRFunction) -> Cfg {
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// 空 IRFunction 退化形态：仅 exit 哨兵一块。
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if f.insts.is_empty() {
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return Cfg {
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blocks: vec![BasicBlock {
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inst_range: 0..0,
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preds: Vec::new(),
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succs: Vec::new(),
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}],
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entry: 0,
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exit: 0,
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};
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}
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let heads = partition::partition_blocks(f);
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let (mut blocks, exit_id) = split::split_and_edges(f, &heads);
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exception::add_exception_edges(f, &mut blocks);
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finalize::finalize(blocks, exit_id)
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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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use oxide_ir::operand::Operand;
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fn succs_total(cfg: &Cfg) -> usize {
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cfg.blocks.iter().map(|b| b.succs.len()).sum()
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}
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fn preds_total(cfg: &Cfg) -> usize {
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cfg.blocks.iter().map(|b| b.preds.len()).sum()
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}
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/// 无跳转线性函数：1 实块 + exit 哨兵，块 0 Fallthrough→exit，preds/succs 对称。
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#[test]
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fn linear_function_is_single_block_plus_exit() {
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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 cfg = build_cfg(&f);
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assert_eq!(cfg.blocks.len(), 2); // 1 实块 + exit 哨兵
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assert_eq!(cfg.entry, 0);
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assert_eq!(cfg.exit, 1);
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assert_eq!(cfg.blocks[0].inst_range, 0..3);
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assert_eq!(cfg.blocks[0].succs, vec![(1, EdgeKind::Fallthrough)]);
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assert!(cfg.blocks[1].succs.is_empty()); // exit 哨兵无出边
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assert_eq!(cfg.blocks[1].preds, vec![0]);
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assert_eq!(succs_total(&cfg), preds_total(&cfg));
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}
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/// if/else 典型形状：条件分裂块（Jump + Fallthrough 双出边），4 实块 + exit 哨兵。
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#[test]
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fn if_else_conditional_jump_splits_block_with_dual_edges() {
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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.push(Inst::call(Operand::Reg(2), Operand::Reg(0), Operand::Reg(3), 1)); // 1: then a()
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f.insts.push(Inst::jmp(1)); // 2: → L1(end)
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f.insts.push(Inst::call(Operand::Reg(4), Operand::Reg(0), Operand::Reg(3), 1)); // 3: else b()
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f.insts
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.push(Inst::new(OpCode::RETURN, Operand::None, Operand::None, Operand::None)); // 4
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f.label_pos = vec![Some(3), Some(4)]; // L0→else 块头(3), L1→end(4)
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f.label_count = 2;
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let cfg = build_cfg(&f);
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assert_eq!(cfg.blocks.len(), 5); // 4 实块 + exit 哨兵
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assert_eq!(cfg.entry, 0);
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assert_eq!(cfg.exit, 4);
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// 块 0（cond）：条件分裂，Jump→else + Fallthrough→then 两条出边都在
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assert_eq!(cfg.blocks[0].inst_range, 0..1);
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assert_eq!(cfg.blocks[0].succs, vec![(2, EdgeKind::Jump), (1, EdgeKind::Fallthrough)]);
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assert!(cfg.blocks[0].preds.is_empty());
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// 块 1（then）：Jump→end
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assert_eq!(cfg.blocks[1].inst_range, 1..3);
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assert_eq!(cfg.blocks[1].succs, vec![(3, EdgeKind::Jump)]);
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assert_eq!(cfg.blocks[1].preds, vec![0]);
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// 块 2（else）：Fallthrough→end
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assert_eq!(cfg.blocks[2].inst_range, 3..4);
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assert_eq!(cfg.blocks[2].succs, vec![(3, EdgeKind::Fallthrough)]);
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assert_eq!(cfg.blocks[2].preds, vec![0]);
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// 块 3（end）：RETURN → Fallthrough→exit
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assert_eq!(cfg.blocks[3].inst_range, 4..5);
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assert_eq!(cfg.blocks[3].succs, vec![(4, EdgeKind::Fallthrough)]);
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assert_eq!(cfg.blocks[3].preds, vec![1, 2]);
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// 块 4（exit 哨兵）：空块 0..0，preds 含块 3，无出边
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assert_eq!(cfg.blocks[4].inst_range, 0..0);
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assert!(cfg.blocks[4].succs.is_empty());
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assert_eq!(cfg.blocks[4].preds, vec![3]);
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assert_eq!(succs_total(&cfg), preds_total(&cfg));
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}
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/// try/catch：TRY_BEGIN 是块内标记不切块，所在 BB 出 Exception 边到 catch 入口。
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#[test]
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fn try_begin_does_not_split_block_and_emits_exception_edge() {
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let mut f = IRFunction::new();
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f.insts.push(Inst::try_begin(0)); // 0: TRY_BEGIN（块内标记）
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f.insts
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.push(Inst::new(OpCode::NOP, Operand::None, Operand::None, Operand::None)); // 1
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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.insts
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.push(Inst::new(OpCode::NOP, Operand::None, Operand::None, Operand::None)); // 3: catch 入口
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f.insts
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.push(Inst::new(OpCode::RETURN, Operand::None, 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 cfg = build_cfg(&f);
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assert_eq!(cfg.blocks.len(), 3); // 2 实块 + exit 哨兵（TRY_BEGIN 不切块）
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assert_eq!(cfg.blocks[0].inst_range, 0..3); // try 体未被切块
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// Exception 边从 TRY_BEGIN 所在 BB 出发指向 catch 入口块。
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assert!(cfg.blocks[0].succs.contains(&(1, EdgeKind::Exception)));
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assert_eq!(cfg.blocks[1].succs, vec![(2, EdgeKind::Fallthrough)]);
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assert_eq!(cfg.blocks[2].preds, vec![0, 1]);
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assert_eq!(succs_total(&cfg), preds_total(&cfg));
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}
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/// try/finally：TRY_FINALLY_BEGIN 同上，Exception 边到 finally 入口块。
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#[test]
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fn try_finally_begin_emits_exception_edge() {
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let mut f = IRFunction::new();
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f.insts.push(Inst::try_finally_begin(0)); // 0
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f.insts
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.push(Inst::new(OpCode::NOP, Operand::None, Operand::None, Operand::None)); // 1
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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.insts
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.push(Inst::new(OpCode::NOP, Operand::None, Operand::None, Operand::None)); // 3: finally 入口
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f.insts
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.push(Inst::new(OpCode::RETURN, Operand::None, 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 cfg = build_cfg(&f);
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assert_eq!(cfg.blocks.len(), 3);
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assert!(cfg.blocks[0].succs.contains(&(1, EdgeKind::Exception)));
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assert_eq!(cfg.blocks[2].preds, vec![0, 1]);
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assert_eq!(succs_total(&cfg), preds_total(&cfg));
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}
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/// 尾部 RETURN：该块 Fallthrough 到 exit。
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#[test]
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fn trailing_return_flows_to_exit() {
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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::RETURN, Operand::None, Operand::None, Operand::None));
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let cfg = build_cfg(&f);
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assert_eq!(cfg.blocks.len(), 2);
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assert_eq!(cfg.blocks[0].succs, vec![(1, EdgeKind::Fallthrough)]);
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assert_eq!(cfg.blocks[1].preds, vec![0]);
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}
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/// 空 IRFunction：退化 CFG，entry == exit == 0，blocks 长度 1。
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#[test]
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fn empty_function_yields_degenerate_cfg() {
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let f = IRFunction::new();
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let cfg = build_cfg(&f);
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assert_eq!(cfg.blocks.len(), 1);
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assert_eq!(cfg.entry, 0);
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assert_eq!(cfg.exit, 0);
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assert_eq!(cfg.blocks[0].inst_range, 0..0);
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assert!(cfg.blocks[0].succs.is_empty());
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assert!(cfg.blocks[0].preds.is_empty());
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}
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/// 幂等性：同一 IR 两次构建结果相等。
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#[test]
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fn build_cfg_is_idempotent() {
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let mut f = IRFunction::new();
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f.insts.push(Inst::jmp_if_false(1, 0)); // 0: → L0（回环目标）
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f.insts.push(Inst::jmp(0)); // 1: → L0
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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), Some(0)]; // L0→2（尾部）, L1→0（回环）
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f.label_count = 2;
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let cfg1 = build_cfg(&f);
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let cfg2 = build_cfg(&f);
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assert_eq!(cfg1, cfg2);
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}
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}
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