//! Inst 寄存器契约：def/use 扫描 + 副作用判定（DCE 与 Phase 5 liveness 共用，D-06）。
//!
//! `def_reg` / `use_regs` / `is_pure` 是 `Inst` 的类型契约方法（`impl Inst` 与 `inst.rs`
//! 中的构造 API 同属一类型），落在 oxide_ir 契约层供 DCE 消费、liveness 复用。
//! 寄存器规则逐条对照 VM dispatch handler（RESEARCH Pattern 1/2 全表）：
//! CALL 隐式写 reg 0、GET_PROP 结果写 a/b 槽、HALT 隐式读 reg 0、None 槽映射 Reg(0)。

use oxide_bytecode::opcode::OpCode;
use smallvec::SmallVec;

use crate::inst::Inst;
use crate::operand::Operand;
use crate::IRFunction;

impl Inst {
    /// 本指令定义的寄存器（None 槽按 Reg(0) 映射；CALL 系含隐式 reg 0）。
    /// 无写入返回 None。
    pub fn def_reg(&self) -> Option<u32> {
        match self.op {
            // CALL 系：结果隐式写 reg 0，rd 是 callee use（Pitfall 1）
            OpCode::CALL | OpCode::CALL_NATIVE => Some(0),
            // GET_PROP 系：结果写 a/b 槽而非 rd（Pitfall 3）
            OpCode::GET_PROP | OpCode::IC_GET_PROP => reg_of(&self.a),
            OpCode::GET_PROP_DYNAMIC => reg_of(&self.b),
            // 成员读写：val 槽原地更新（a 槽 / b 槽）
            OpCode::MEMBER_INC | OpCode::MEMBER_DEC => reg_of(&self.a),
            OpCode::DYN_MEMBER_INC | OpCode::DYN_MEMBER_DEC => reg_of(&self.b),
            OpCode::COMPOUND_MEMBER_ADD
            | OpCode::COMPOUND_MEMBER_SUB
            | OpCode::COMPOUND_MEMBER_MUL
            | OpCode::COMPOUND_MEMBER_DIV
            | OpCode::COMPOUND_MEMBER_MOD
            | OpCode::COMPOUND_MEMBER_EXP => reg_of(&self.a),
            // 无 def：控制流 / 写共享状态 / 纯写对象
            OpCode::HALT
            | OpCode::RETURN
            | OpCode::THROW
            | OpCode::JMP
            | OpCode::JMP_IF_FALSE
            | OpCode::JMP_IF_TRUE
            | OpCode::JMP_IF_NULLISH
            | OpCode::TRY_BEGIN
            | OpCode::TRY_END
            | OpCode::TRY_FINALLY_BEGIN
            | OpCode::TRY_FINALLY_END
            | OpCode::MAKE_CELL
            | OpCode::CELL_SET
            | OpCode::STORE_UPVALUE
            | OpCode::SET_PROP
            | OpCode::SET_PROP_DYNAMIC
            | OpCode::IC_SET_PROP
            | OpCode::SET_ELEM
            | OpCode::GET_PRIVATE
            | OpCode::SET_PRIVATE
            | OpCode::INIT_PRIVATE
            | OpCode::PRIVATE_BRAND_IN
            | OpCode::DELETE_PROP_STATIC
            | OpCode::DELETE_PROP_DYNAMIC
            | OpCode::DEFINE_ACCESSOR
            | OpCode::SET_HOME_OBJECT
            | OpCode::FOR_IN_INIT
            | OpCode::FOR_OF_INIT
            | OpCode::FOR_IN_CLEANUP
            | OpCode::FOR_OF_CLOSE => None,
            // 其余指令 rd 即 def（算术/比较/位/逻辑/加载族/迭代器 NEXT 等）
            _ => reg_of(&self.rd),
        }
    }

    /// 本指令读取的寄存器（None 槽按 Reg(0) 映射；HALT 特判 reg 0；TEMPLATE_STR 解析 ext）。
    pub fn use_regs(&self) -> SmallVec<[u32; 4]> {
        let mut uses = SmallVec::new();
        match self.op {
            // CALL 系：rd=callee, a=this, b..b+nargs 参数区间（Pitfall 1）
            OpCode::CALL | OpCode::CALL_NATIVE => {
                push_operand(&mut uses, &self.rd);
                push_operand(&mut uses, &self.a);
                let nargs = self.ext.first().copied().unwrap_or(0);
                push_range(&mut uses, reg_of(&self.b), nargs);
            }
            // NEW_EXPRESSION：a=ctor, b..b+nargs
            OpCode::NEW_EXPRESSION => {
                push_operand(&mut uses, &self.a);
                let nargs = self.ext.first().copied().unwrap_or(0);
                push_range(&mut uses, reg_of(&self.b), nargs);
            }
            // SUPER_CALL：a..a+nargs
            OpCode::SUPER_CALL => {
                let nargs = self.ext.first().copied().unwrap_or(0);
                push_range(&mut uses, reg_of(&self.a), nargs);
            }
            // GET_PROP 系：结果写 a/b 槽，rd=obj 是 use（Pitfall 3）
            OpCode::GET_PROP => {
                push_operand(&mut uses, &self.rd);
                push_operand(&mut uses, &self.b);
            }
            OpCode::GET_PROP_DYNAMIC => {
                push_operand(&mut uses, &self.rd);
                push_operand(&mut uses, &self.a);
            }
            OpCode::IC_GET_PROP => {
                push_operand(&mut uses, &self.a);
                push_operand(&mut uses, &self.b);
            }
            // 成员更新：obj + key 是 use，val 槽是 def
            OpCode::MEMBER_INC | OpCode::MEMBER_DEC => {
                push_operand(&mut uses, &self.rd);
                push_operand(&mut uses, &self.b);
            }
            OpCode::DYN_MEMBER_INC | OpCode::DYN_MEMBER_DEC => {
                push_operand(&mut uses, &self.rd);
                push_operand(&mut uses, &self.a);
            }
            OpCode::COMPOUND_MEMBER_ADD
            | OpCode::COMPOUND_MEMBER_SUB
            | OpCode::COMPOUND_MEMBER_MUL
            | OpCode::COMPOUND_MEMBER_DIV
            | OpCode::COMPOUND_MEMBER_MOD
            | OpCode::COMPOUND_MEMBER_EXP => {
                push_operand(&mut uses, &self.rd);
                push_operand(&mut uses, &self.a);
                push_operand(&mut uses, &self.b);
            }
            // 复合赋值：rd 与 a 都是 use（coerce 读双寄存器）
            OpCode::COMPOUND_ADD
            | OpCode::COMPOUND_SUB
            | OpCode::COMPOUND_MUL
            | OpCode::COMPOUND_DIV
            | OpCode::COMPOUND_MOD
            | OpCode::COMPOUND_EXP
            | OpCode::COMPOUND_AND
            | OpCode::COMPOUND_OR
            | OpCode::COMPOUND_XOR
            | OpCode::COMPOUND_SHL
            | OpCode::COMPOUND_SHR
            | OpCode::COMPOUND_USHR => {
                push_operand(&mut uses, &self.rd);
                push_operand(&mut uses, &self.a);
            }
            // 自增/自减：读 rd（写 rd 和 a）
            OpCode::INC_PRE | OpCode::INC_POST | OpCode::DEC_PRE | OpCode::DEC_POST => {
                push_operand(&mut uses, &self.rd);
            }
            // 二元运算：a, b
            OpCode::ADD | OpCode::SUB | OpCode::MUL | OpCode::DIV | OpCode::MOD | OpCode::EQ
            | OpCode::NEQ | OpCode::LT | OpCode::GT | OpCode::LTE | OpCode::GTE | OpCode::AND
            | OpCode::OR | OpCode::NULLISH | OpCode::STRICT_EQ | OpCode::STRICT_NEQ
            | OpCode::BIT_AND | OpCode::BIT_OR | OpCode::BIT_XOR | OpCode::SHL | OpCode::SHR
            | OpCode::USHR | OpCode::INSTANCEOF | OpCode::IN | OpCode::CREATE_REGEXP => {
                push_operand(&mut uses, &self.a);
                push_operand(&mut uses, &self.b);
            }
            // 一元：a（emit 常 rd==a）
            OpCode::NEG | OpCode::NOT | OpCode::UNARY_PLUS | OpCode::BIT_NOT | OpCode::TYPEOF => {
                push_operand(&mut uses, &self.a);
            }
            // 无条件跳转 / try 标记：b 是 Label，无寄存器
            OpCode::JMP | OpCode::TRY_BEGIN | OpCode::TRY_FINALLY_BEGIN | OpCode::TRY_END
            | OpCode::TRY_FINALLY_END | OpCode::FOR_IN_CLEANUP | OpCode::FOR_OF_CLOSE => {}
            // 条件跳转：rd=cond
            OpCode::JMP_IF_FALSE | OpCode::JMP_IF_TRUE | OpCode::JMP_IF_NULLISH => {
                push_operand(&mut uses, &self.rd);
            }
            // HALT：隐式读 reg 0（顶层返回值，Pitfall 2）
            OpCode::HALT => uses.push(0),
            // RETURN/THROW：读 rd（None→0）
            OpCode::RETURN | OpCode::THROW => push_operand(&mut uses, &self.rd),
            // 加载族：a 槽是 Const/Imm 立即数，无寄存器 use
            OpCode::LOAD_CONST | OpCode::CREATE_CLOSURE | OpCode::LOAD_UPVALUE | OpCode::VOID
            | OpCode::NEW_OBJECT | OpCode::NEW_ARRAY | OpCode::NOP => {}
            // 变量读写：LOAD_VAR/STORE_VAR/CELL_GET 读 a（None→0）
            OpCode::LOAD_VAR | OpCode::STORE_VAR | OpCode::CELL_GET => {
                push_operand(&mut uses, &self.a);
            }
            // MAKE_CELL：cell 初值读 rd；CELL_SET/STORE_UPVALUE 读 a
            OpCode::MAKE_CELL => push_operand(&mut uses, &self.rd),
            OpCode::CELL_SET | OpCode::STORE_UPVALUE => push_operand(&mut uses, &self.a),
            // 写对象属性：rd/a/b 全 use
            OpCode::SET_PROP | OpCode::SET_PROP_DYNAMIC | OpCode::IC_SET_PROP | OpCode::SET_ELEM
            | OpCode::GET_PRIVATE | OpCode::SET_PRIVATE | OpCode::INIT_PRIVATE
            | OpCode::PRIVATE_BRAND_IN | OpCode::DEFINE_ACCESSOR => {
                push_operand(&mut uses, &self.rd);
                push_operand(&mut uses, &self.a);
                push_operand(&mut uses, &self.b);
            }
            // delete：读 obj（+dynamic 读 key）
            OpCode::DELETE_PROP_STATIC => push_operand(&mut uses, &self.rd),
            OpCode::DELETE_PROP_DYNAMIC => {
                push_operand(&mut uses, &self.rd);
                push_operand(&mut uses, &self.b);
            }
            // super 属性读：a=this, b=key
            OpCode::SUPER_GET_PROP | OpCode::SUPER_STATIC_GET_PROP => {
                push_operand(&mut uses, &self.a);
                push_operand(&mut uses, &self.b);
            }
            // SET_HOME_OBJECT：rd=func, a=home
            OpCode::SET_HOME_OBJECT => {
                push_operand(&mut uses, &self.rd);
                push_operand(&mut uses, &self.a);
            }
            // for-in/of 迭代器：INIT 读 a；NEXT/DONE 读迭代器栈隐式状态
            OpCode::FOR_IN_INIT | OpCode::FOR_OF_INIT => push_operand(&mut uses, &self.a),
            OpCode::FOR_IN_NEXT | OpCode::FOR_IN_DONE | OpCode::FOR_OF_NEXT | OpCode::FOR_OF_DONE => {}
            // REST_OBJECT：读 a（ext 是 excluded_idx 常量）
            OpCode::REST_OBJECT => push_operand(&mut uses, &self.a),
            // TEMPLATE_STR：解析 ext，跳过 ext[0]，后续 seg>>31==1 则低 8 位是 expr_reg（A1）
            OpCode::TEMPLATE_STR => {
                for seg in self.ext.iter().skip(1) {
                    if seg >> 31 == 1 {
                        uses.push(seg & 0xFF);
                    }
                }
            }
            // 占位 opcode（emit 不产）：按无 use 保守处理，不影响合法产物
            OpCode::SWITCH_TABLE | OpCode::PROFILE_TYPE | OpCode::PROFILE_SHAPE
            | OpCode::PROFILE_BRANCH | OpCode::PROFILE_CALL | OpCode::FORK | OpCode::JOIN => {}
        }
        uses
    }

    /// 本指令是否无观察副作用（Pattern 1 纯表；LOAD_VAR 的 This+derived 特判需 &IRFunction）。
    ///
    /// 纯 = 结果未用时可删。表外 opcode 一律有副作用（D-05 精确表，宁少删不错删）。
    pub fn is_pure(&self, f: &IRFunction) -> bool {
        match self.op {
            // 算术 / 比较 / 位 / 逻辑：coerce 对象路径有抛错风险，D-05 决策算纯（运行时等价兜底）
            OpCode::ADD | OpCode::SUB | OpCode::MUL | OpCode::DIV | OpCode::MOD | OpCode::NEG
            | OpCode::UNARY_PLUS | OpCode::EQ | OpCode::NEQ | OpCode::LT | OpCode::GT
            | OpCode::LTE | OpCode::GTE | OpCode::STRICT_EQ | OpCode::STRICT_NEQ
            | OpCode::BIT_AND | OpCode::BIT_OR | OpCode::BIT_XOR | OpCode::SHL | OpCode::SHR
            | OpCode::USHR | OpCode::BIT_NOT | OpCode::AND | OpCode::OR | OpCode::NOT
            | OpCode::NULLISH => true,
            // 分配 / 常量 / 空操作（a 槽非寄存器）
            OpCode::NOP | OpCode::LOAD_CONST | OpCode::VOID | OpCode::TYPEOF | OpCode::NEW_OBJECT
            | OpCode::NEW_ARRAY => true,
            // 闭包 / cell 读取：无抛错路径（D-07）
            OpCode::CREATE_CLOSURE | OpCode::LOAD_UPVALUE | OpCode::CELL_GET => true,
            // 模板字符串：纯拼接写 rd，无抛错（use 统计覆盖其 ext）
            OpCode::TEMPLATE_STR => true,
            // LOAD_VAR：仅 a==This 且 derived 构造函数读 this 可能抛 ReferenceError（misc.rs:52-63）
            OpCode::LOAD_VAR => {
                !(self.a == Operand::This && f.is_derived_constructor)
            }
            // STORE_VAR：写变量目标寄存器。脚本顶层/模块作用域的变量是**全局可观察状态**
            // （Pitfall 6：`let x=0; class C{[x=1](){}}` 无后续本地读取时删除 `x=1` 会改变
            // 外部 `assert(x===1)` 的观察结果）；函数内局部未用赋值的优化留给 Phase 5 精确活度。
            OpCode::STORE_VAR => false,
            // 其余全部有副作用（getter/调用/控制流/迭代器/复合更新/写共享状态/占位防御）
            _ => false,
        }
    }
}

/// 操作数 → 物理寄存器号。None 槽映射 reg 0（A3，与 lower.rs operand_to_u8 一致）；
/// Const/Imm/Label 不是寄存器槽，返回 None。
fn reg_of(o: &Operand) -> Option<u32> {
    match o {
        Operand::Reg(r) => Some(*r),
        Operand::This => Some(254),
        Operand::NewTarget => Some(255),
        Operand::None => Some(0),
        Operand::Const(_) | Operand::Imm(_) | Operand::Label(_) => None,
    }
}

/// 把寄存器操作数推入 use 集合（非寄存器槽跳过）。
fn push_operand(uses: &mut SmallVec<[u32; 4]>, o: &Operand) {
    if let Some(r) = reg_of(o) {
        uses.push(r);
    }
}

/// 推入连续参数区间 [first, first+nargs)。
fn push_range(uses: &mut SmallVec<[u32; 4]>, first: Option<u32>, nargs: u32) {
    if let Some(f) = first {
        uses.extend((0..nargs).map(|i| f + i));
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::inst::Inst;
    use crate::operand::Operand;
    use crate::IRFunction;

    // ── def_reg / use_regs 契约测试（Pattern 2 全表，反直觉槽位锁定）──

    #[test]
    fn binary_op_def_rd_use_ab() {
        let inst = Inst::new(OpCode::ADD, Operand::Reg(0), Operand::Reg(1), Operand::Reg(2));
        assert_eq!(inst.def_reg(), Some(0));
        assert_eq!(inst.use_regs().as_slice(), &[1, 2]);
    }

    #[test]
    fn unary_op_def_rd_use_a() {
        let inst = Inst::new(OpCode::NEG, Operand::Reg(0), Operand::Reg(1), Operand::None);
        assert_eq!(inst.def_reg(), Some(0));
        assert_eq!(inst.use_regs().as_slice(), &[1]);
    }

    #[test]
    fn get_prop_def_is_a_slot_not_rd() {
        // Pitfall 3：GET_PROP rd=obj 是 use，结果写 a 槽
        let inst = Inst::new(OpCode::GET_PROP, Operand::Reg(0), Operand::Reg(1), Operand::Reg(2));
        assert_eq!(inst.def_reg(), Some(1));
        assert_eq!(inst.use_regs().as_slice(), &[0, 2]);
    }

    #[test]
    fn get_prop_dynamic_def_is_b_slot() {
        // Pitfall 3：GET_PROP_DYNAMIC rd=obj 是 use，结果写 b 槽
        let inst = Inst::new(OpCode::GET_PROP_DYNAMIC, Operand::Reg(0), Operand::Reg(1), Operand::Reg(2));
        assert_eq!(inst.def_reg(), Some(2));
        assert_eq!(inst.use_regs().as_slice(), &[0, 1]);
    }

    #[test]
    fn ic_get_prop_a_slot_is_use_and_def() {
        // Pitfall 3：IC_GET_PROP a 槽既是对象 use 又是结果 def
        let inst = Inst::ic_get(Operand::Reg(1), Operand::Reg(2));
        assert_eq!(inst.def_reg(), Some(1));
        let uses = inst.use_regs();
        assert_eq!(uses.as_slice(), &[1, 2]);
    }

    #[test]
    fn call_def_is_implicit_reg0_with_arg_range() {
        // Pitfall 1：CALL rd=callee 是 use，结果隐式写 reg 0；参数 b..b+nargs 连续
        let inst = Inst::call(Operand::Reg(0), Operand::Reg(1), Operand::Reg(2), 3);
        assert_eq!(inst.def_reg(), Some(0));
        assert_eq!(inst.use_regs().as_slice(), &[0, 1, 2, 3, 4]);
    }

    #[test]
    fn call_native_def_is_implicit_reg0() {
        let inst = Inst::call_native(Operand::Reg(0), Operand::Reg(1), Operand::Reg(2), 1);
        assert_eq!(inst.def_reg(), Some(0));
        assert_eq!(inst.use_regs().as_slice(), &[0, 1, 2]);
    }

    #[test]
    fn new_expression_uses_ctor_and_arg_range() {
        let inst = Inst::new_expression(Operand::Reg(3), Operand::Reg(0), Operand::Reg(1), 2);
        assert_eq!(inst.def_reg(), Some(3));
        assert_eq!(inst.use_regs().as_slice(), &[0, 1, 2]);
    }

    #[test]
    fn super_call_uses_arg_range() {
        let inst = Inst::super_call(Operand::Reg(3), Operand::Reg(1), 1);
        assert_eq!(inst.def_reg(), Some(3));
        assert_eq!(inst.use_regs().as_slice(), &[1]);
    }

    #[test]
    fn halt_implicitly_uses_reg0() {
        // Pitfall 2：HALT 返回 regs[0]，顶层 LOAD_VAR(None, r) 链靠它保活
        let inst = Inst::new(OpCode::HALT, Operand::None, Operand::None, Operand::None);
        assert_eq!(inst.def_reg(), None);
        assert_eq!(inst.use_regs().as_slice(), &[0]);
    }

    #[test]
    fn void_defs_rd_no_use() {
        // VM 的 VOID handler 不读 a 槽
        let inst = Inst::new(OpCode::VOID, Operand::Reg(1), Operand::Reg(2), Operand::None);
        assert_eq!(inst.def_reg(), Some(1));
        assert!(inst.use_regs().is_empty());
    }

    #[test]
    fn load_const_create_closure_load_upvalue_no_use() {
        // a 槽是 Const/Imm 立即数，非寄存器
        let lc = Inst::load_const(Operand::Reg(1), 5);
        assert_eq!(lc.def_reg(), Some(1));
        assert!(lc.use_regs().is_empty());

        let cc = Inst::create_closure(Operand::Reg(1), 0);
        assert_eq!(cc.def_reg(), Some(1));
        assert!(cc.use_regs().is_empty());

        let lu = Inst::new(OpCode::LOAD_UPVALUE, Operand::Reg(1), Operand::Imm(0), Operand::None);
        assert_eq!(lu.def_reg(), Some(1));
        assert!(lu.use_regs().is_empty());
    }

    #[test]
    fn none_slot_maps_to_reg0() {
        // A3：None 槽与 lower.rs operand_to_u8 一致，统一映射物理 reg 0
        let lv = Inst::new(OpCode::LOAD_VAR, Operand::Reg(1), Operand::None, Operand::None);
        assert_eq!(lv.use_regs().as_slice(), &[0]);

        let cg = Inst::new(OpCode::CELL_GET, Operand::Reg(0), Operand::None, Operand::Imm(0));
        assert_eq!(cg.use_regs().as_slice(), &[0]);
    }

    #[test]
    fn template_str_parses_expr_regs_from_ext() {
        // ext[0] 跳过；后续 seg>>31==1 则低 8 位是 expr_reg（A1，emit 8 位编码）
        let with_expr = Inst::template_str(Operand::Reg(1), 2, 10, &[0x1234, 0x8000_0000 | 5]);
        assert_eq!(with_expr.use_regs().as_slice(), &[5]);

        // 纯 quasi（无表达式）：不误报寄存器
        let no_expr = Inst::template_str(Operand::Reg(1), 1, 10, &[0x1234]);
        assert!(no_expr.use_regs().is_empty());
    }

    #[test]
    fn jmp_if_false_uses_cond_reg() {
        let inst = Inst::jmp_if_false(3, 9);
        assert_eq!(inst.def_reg(), None);
        assert_eq!(inst.use_regs().as_slice(), &[3]);
    }

    #[test]
    fn jmp_and_try_no_use() {
        assert!(Inst::jmp(9).use_regs().is_empty());
        assert!(Inst::try_begin(9).use_regs().is_empty());
        assert!(Inst::try_finally_begin(9).use_regs().is_empty());
    }

    #[test]
    fn make_cell_no_def_uses_rd() {
        let inst = Inst::new(OpCode::MAKE_CELL, Operand::Reg(5), Operand::None, Operand::None);
        assert_eq!(inst.def_reg(), None);
        assert_eq!(inst.use_regs().as_slice(), &[5]);
    }

    #[test]
    fn cell_set_and_store_upvalue_use_a_no_def() {
        let cs = Inst::new(OpCode::CELL_SET, Operand::None, Operand::Reg(1), Operand::Imm(0));
        assert_eq!(cs.def_reg(), None);
        assert_eq!(cs.use_regs().as_slice(), &[1]);

        let su = Inst::new(OpCode::STORE_UPVALUE, Operand::None, Operand::Reg(1), Operand::Imm(0));
        assert_eq!(su.def_reg(), None);
        assert_eq!(su.use_regs().as_slice(), &[1]);
    }

    #[test]
    fn return_throw_use_rd_with_none_mapping_reg0() {
        let ret = Inst::new(OpCode::RETURN, Operand::None, Operand::None, Operand::None);
        assert_eq!(ret.def_reg(), None);
        assert_eq!(ret.use_regs().as_slice(), &[0]);

        let thr = Inst::new(OpCode::THROW, Operand::Reg(2), Operand::None, Operand::None);
        assert_eq!(thr.def_reg(), None);
        assert_eq!(thr.use_regs().as_slice(), &[2]);
    }

    #[test]
    fn rest_object_uses_a() {
        let inst = Inst::rest_object(Operand::Reg(0), Operand::Reg(1), 7);
        assert_eq!(inst.def_reg(), Some(0));
        assert_eq!(inst.use_regs().as_slice(), &[1]);
    }

    #[test]
    fn for_in_next_defs_rd_no_use() {
        let inst = Inst::new(OpCode::FOR_IN_NEXT, Operand::Reg(0), Operand::None, Operand::None);
        assert_eq!(inst.def_reg(), Some(0));
        assert!(inst.use_regs().is_empty());
    }

    #[test]
    fn store_var_def_rd_use_a() {
        let inst = Inst::new(OpCode::STORE_VAR, Operand::Reg(0), Operand::Reg(1), Operand::None);
        assert_eq!(inst.def_reg(), Some(0));
        assert_eq!(inst.use_regs().as_slice(), &[1]);
    }

    // ── is_pure 契约测试（Pattern 1 表，纯/非纯族代表 opcode）──

    #[test]
    fn pure_ops_are_deletable() {
        let f = IRFunction::new();
        // 算术 / 比较 / 位 / 逻辑
        assert!(Inst::new(OpCode::ADD, Operand::Reg(0), Operand::Reg(1), Operand::Reg(2)).is_pure(&f));
        assert!(Inst::new(OpCode::SUB, Operand::Reg(0), Operand::Reg(1), Operand::Reg(2)).is_pure(&f));
        assert!(Inst::new(OpCode::MUL, Operand::Reg(0), Operand::Reg(1), Operand::Reg(2)).is_pure(&f));
        assert!(Inst::new(OpCode::NEG, Operand::Reg(0), Operand::Reg(1), Operand::None).is_pure(&f));
        assert!(Inst::new(OpCode::EQ, Operand::Reg(0), Operand::Reg(1), Operand::Reg(2)).is_pure(&f));
        assert!(Inst::new(OpCode::STRICT_EQ, Operand::Reg(0), Operand::Reg(1), Operand::Reg(2)).is_pure(&f));
        assert!(Inst::new(OpCode::LT, Operand::Reg(0), Operand::Reg(1), Operand::Reg(2)).is_pure(&f));
        assert!(Inst::new(OpCode::BIT_AND, Operand::Reg(0), Operand::Reg(1), Operand::Reg(2)).is_pure(&f));
        assert!(Inst::new(OpCode::BIT_NOT, Operand::Reg(0), Operand::Reg(1), Operand::None).is_pure(&f));
        assert!(Inst::new(OpCode::AND, Operand::Reg(0), Operand::Reg(1), Operand::Reg(2)).is_pure(&f));
        assert!(Inst::new(OpCode::OR, Operand::Reg(0), Operand::Reg(1), Operand::Reg(2)).is_pure(&f));
        assert!(Inst::new(OpCode::NOT, Operand::Reg(0), Operand::Reg(1), Operand::None).is_pure(&f));
        assert!(Inst::new(OpCode::NULLISH, Operand::Reg(0), Operand::Reg(1), Operand::Reg(2)).is_pure(&f));
        // 分配/常量/空操作
        assert!(Inst::new(OpCode::NOP, Operand::None, Operand::None, Operand::None).is_pure(&f));
        assert!(Inst::load_const(Operand::Reg(1), 0).is_pure(&f));
        assert!(Inst::new(OpCode::VOID, Operand::Reg(1), Operand::None, Operand::None).is_pure(&f));
        assert!(Inst::new(OpCode::TYPEOF, Operand::Reg(1), Operand::Reg(2), Operand::None).is_pure(&f));
        assert!(Inst::new(OpCode::NEW_OBJECT, Operand::Reg(1), Operand::None, Operand::None).is_pure(&f));
        assert!(Inst::new(OpCode::NEW_ARRAY, Operand::Reg(1), Operand::None, Operand::None).is_pure(&f));
        // 闭包/单元读取
        assert!(Inst::create_closure(Operand::Reg(1), 0).is_pure(&f));
        assert!(Inst::new(OpCode::LOAD_UPVALUE, Operand::Reg(1), Operand::Imm(0), Operand::None).is_pure(&f));
        assert!(Inst::new(OpCode::CELL_GET, Operand::Reg(0), Operand::Reg(1), Operand::Imm(0)).is_pure(&f));
        // 模板字符串
        assert!(Inst::template_str(Operand::Reg(1), 1, 10, &[0x1234]).is_pure(&f));
        // LOAD_VAR 普通（a=Reg）纯
        assert!(Inst::new(OpCode::LOAD_VAR, Operand::Reg(1), Operand::Reg(2), Operand::None).is_pure(&f));
        // STORE_VAR 一律有副作用（Pitfall 6：顶层变量赋值全局可观察，不删）
        assert!(!Inst::new(OpCode::STORE_VAR, Operand::Reg(0), Operand::Reg(1), Operand::None).is_pure(&f));
        assert!(!Inst::new(OpCode::STORE_VAR, Operand::Reg(0), Operand::Reg(1), Operand::Imm(0)).is_pure(&f));
        assert!(!Inst::new(OpCode::STORE_VAR, Operand::Reg(0), Operand::Reg(1), Operand::Imm(1)).is_pure(&f));
    }

    #[test]
    fn impure_ops_are_not_deletable() {
        let f = IRFunction::new();
        // getter / 写对象属性
        assert!(!Inst::ic_get(Operand::Reg(1), Operand::Reg(2)).is_pure(&f));
        assert!(!Inst::new(OpCode::GET_PROP, Operand::Reg(0), Operand::Reg(1), Operand::Reg(2)).is_pure(&f));
        assert!(!Inst::new(OpCode::GET_PROP_DYNAMIC, Operand::Reg(0), Operand::Reg(1), Operand::Reg(2)).is_pure(&f));
        assert!(!Inst::ic_set(Operand::Reg(0), Operand::Reg(1), Operand::Reg(2)).is_pure(&f));
        assert!(!Inst::new(OpCode::SET_PROP, Operand::Reg(0), Operand::Reg(1), Operand::Reg(2)).is_pure(&f));
        assert!(!Inst::new(OpCode::SUPER_GET_PROP, Operand::Reg(0), Operand::Reg(1), Operand::Reg(2)).is_pure(&f));
        assert!(!Inst::new(OpCode::DEFINE_ACCESSOR, Operand::Reg(0), Operand::Reg(1), Operand::Reg(2)).is_pure(&f));
        assert!(!Inst::new(OpCode::DELETE_PROP_STATIC, Operand::Reg(0), Operand::Reg(0), Operand::None).is_pure(&f));
        assert!(!Inst::new(OpCode::DELETE_PROP_DYNAMIC, Operand::Reg(0), Operand::None, Operand::Reg(2)).is_pure(&f));
        // 调用 / 异常 / 控制流
        assert!(!Inst::call(Operand::Reg(0), Operand::Reg(1), Operand::Reg(2), 0).is_pure(&f));
        assert!(!Inst::call_native(Operand::Reg(0), Operand::Reg(1), Operand::Reg(2), 0).is_pure(&f));
        assert!(!Inst::new_expression(Operand::Reg(3), Operand::Reg(0), Operand::Reg(1), 0).is_pure(&f));
        assert!(!Inst::super_call(Operand::Reg(3), Operand::Reg(1), 0).is_pure(&f));
        assert!(!Inst::new(OpCode::CREATE_REGEXP, Operand::Reg(0), Operand::Reg(1), Operand::Reg(2)).is_pure(&f));
        assert!(!Inst::new(OpCode::RETURN, Operand::None, Operand::None, Operand::None).is_pure(&f));
        assert!(!Inst::new(OpCode::THROW, Operand::Reg(2), Operand::None, Operand::None).is_pure(&f));
        assert!(!Inst::new(OpCode::HALT, Operand::None, Operand::None, Operand::None).is_pure(&f));
        assert!(!Inst::jmp(9).is_pure(&f));
        assert!(!Inst::jmp_if_false(3, 9).is_pure(&f));
        assert!(!Inst::try_begin(9).is_pure(&f));
        assert!(!Inst::try_finally_begin(9).is_pure(&f));
        // 迭代器 / 复合更新 / 写共享状态
        assert!(!Inst::new(OpCode::FOR_IN_NEXT, Operand::Reg(0), Operand::None, Operand::None).is_pure(&f));
        assert!(!Inst::new(OpCode::FOR_OF_NEXT, Operand::Reg(0), Operand::None, Operand::None).is_pure(&f));
        assert!(!Inst::new(OpCode::INC_PRE, Operand::Reg(0), Operand::Reg(0), Operand::None).is_pure(&f));
        assert!(!Inst::new(OpCode::COMPOUND_ADD, Operand::Reg(0), Operand::Reg(1), Operand::None).is_pure(&f));
        assert!(!Inst::new(OpCode::MEMBER_INC, Operand::Reg(0), Operand::Reg(1), Operand::Reg(2)).is_pure(&f));
        assert!(!Inst::new(OpCode::COMPOUND_MEMBER_ADD, Operand::Reg(0), Operand::Reg(1), Operand::Reg(2)).is_pure(&f));
        assert!(!Inst::rest_object(Operand::Reg(0), Operand::Reg(1), 7).is_pure(&f));
        assert!(!Inst::new(OpCode::INSTANCEOF, Operand::Reg(0), Operand::Reg(1), Operand::Reg(2)).is_pure(&f));
        assert!(!Inst::new(OpCode::IN, Operand::Reg(0), Operand::Reg(1), Operand::Reg(2)).is_pure(&f));
        assert!(!Inst::new(OpCode::GET_PRIVATE, Operand::Reg(0), Operand::Reg(1), Operand::Reg(2)).is_pure(&f));
        assert!(!Inst::new(OpCode::SET_HOME_OBJECT, Operand::Reg(0), Operand::Reg(1), Operand::None).is_pure(&f));
        assert!(!Inst::new(OpCode::STORE_UPVALUE, Operand::None, Operand::Reg(1), Operand::Imm(0)).is_pure(&f));
        assert!(!Inst::new(OpCode::CELL_SET, Operand::None, Operand::Reg(1), Operand::Imm(0)).is_pure(&f));
        assert!(!Inst::new(OpCode::MAKE_CELL, Operand::Reg(5), Operand::None, Operand::None).is_pure(&f));
        // 占位 opcode 防御性有副作用
        assert!(!Inst::new(OpCode::SWITCH_TABLE, Operand::None, Operand::None, Operand::None).is_pure(&f));
    }

    #[test]
    fn store_var_all_branches_are_impure() {
        // Pitfall 6：STORE_VAR 写目标变量寄存器，顶层/模块作用域变量全局可观察，一律不删
        // （const guard 抛错、普通 var/let 赋值都可能改变外部观察状态）
        let f = IRFunction::new();
        assert!(!Inst::new(OpCode::STORE_VAR, Operand::Reg(0), Operand::Reg(1), Operand::None).is_pure(&f));
        assert!(!Inst::new(OpCode::STORE_VAR, Operand::Reg(0), Operand::Reg(1), Operand::Imm(0)).is_pure(&f));
        assert!(!Inst::new(OpCode::STORE_VAR, Operand::Reg(0), Operand::Reg(1), Operand::Imm(1)).is_pure(&f));
    }

    #[test]
    fn load_var_this_derived_constructor_special_case() {
        // a==This + is_derived_constructor 时读 this 可能抛 ReferenceError，不可删
        let mut derived = IRFunction::new();
        derived.is_derived_constructor = true;
        let non_derived = IRFunction::new();

        let this_load = Inst::new(OpCode::LOAD_VAR, Operand::Reg(1), Operand::This, Operand::None);
        assert!(!this_load.is_pure(&derived));
        assert!(this_load.is_pure(&non_derived));

        // a=Reg 普通 LOAD_VAR 在 derived 函数中也纯
        let reg_load = Inst::new(OpCode::LOAD_VAR, Operand::Reg(1), Operand::Reg(2), Operand::None);
        assert!(reg_load.is_pure(&derived));
    }
}