luaur-code-gen 0.1.3

use crate::enums::ir_cmd::IrCmd;
use crate::enums::ir_op_kind::IrOpKind;
use crate::macros::op_a::op_a;
use crate::macros::op_b::op_b;
use crate::records::ir_builder::IrBuilder;
use crate::records::ir_op::IrOp;
use luaur_vm::enums::lua_type::lua_Type;

pub fn get_loop_step_k(build: &mut IrBuilder, ra: i32) -> IrOp {
    let active_block_idx = build.active_block_idx as usize;
    let active = &build.function.blocks[active_block_idx];

    if active.start + 2 <= build.function.instructions.len() as u32 {
        let instructions_size = build.function.instructions.len();
        let mut sv = build.function.instructions[instructions_size - 2].clone();
        let mut st = build.function.instructions[instructions_size - 1].clone();

        // We currently expect to match IR generated from LOADN/LOADK so we match a particular sequence of opcodes
        // In the future this can be extended to cover opposite STORE order as well as STORE_SPLIT_TVALUE
        if sv.cmd == IrCmd::STORE_DOUBLE
            && op_a(&mut sv).kind() == IrOpKind::VmReg
            && op_a(&mut sv).index() == (ra + 1) as u32
            && op_b(sv.clone()).kind() == IrOpKind::Constant
            && st.cmd == IrCmd::STORE_TAG
            && op_a(&mut st).kind() == IrOpKind::VmReg
            && op_a(&mut st).index() == (ra + 1) as u32
            && build.function.tag_op(op_b(st.clone())) == lua_Type::LUA_TNUMBER as u8
        {
            return op_b(sv);
        }
    }

    build.undef()
}