#include "EliminateFrameIndices.h"
#include "RISCv64ISel.h"
#include <cassert>

namespace sysy {

unsigned EliminateFrameIndicesPass::getTypeSizeInBytes(Type* type) {
    if (!type) {
        assert(false && "Cannot get size of a null type.");
        return 0;
    }

    switch (type->getKind()) {
        case Type::kInt:
        case Type::kFloat:
            return 4;
        case Type::kPointer:
            return 8;
        case Type::kArray: {
            auto arrayType = type->as<ArrayType>();
            return arrayType->getNumElements() * getTypeSizeInBytes(arrayType->getElementType());
        }
        default:
            assert(false && "Unsupported type for size calculation.");
            return 0;
    }
}

void EliminateFrameIndicesPass::runOnMachineFunction(MachineFunction* mfunc) {
    StackFrameInfo& frame_info = mfunc->getFrameInfo();
    Function* F = mfunc->getFunc();
    RISCv64ISel* isel = mfunc->getISel();
    
    // 1. 为栈传递的参数计算偏移量
    if (F) {
        int arg_idx = 0;
        for (Argument* arg : F->getArguments()) {
            // 只关心第8个索引及之后的参数 (即第9个参数开始)
            if (arg_idx >= 8) {
                // 第一个栈参数(idx=8)在0(s0), 第二个(idx=9)在8(s0)
                int offset = (arg_idx - 8) * 8;
                unsigned vreg = isel->getVReg(arg);
                frame_info.alloca_offsets[vreg] = offset;
            }
            arg_idx++;
        }
    }

    // 2. 为局部变量分配空间，起始点在 [ra, s0] (16字节) 之后
    int local_var_offset = 16;
    
    // 处理局部变量 (AllocaInst)
    if(F) { // 确保函数指针有效
        for (auto& bb : F->getBasicBlocks()) {
            for (auto& inst : bb->getInstructions()) {
                if (auto alloca = dynamic_cast<AllocaInst*>(inst.get())) {
                    Type* allocated_type = alloca->getType()->as<PointerType>()->getBaseType();
                    int size = getTypeSizeInBytes(allocated_type);
                    
                    // RISC-V要求栈地址8字节对齐
                    size = (size + 7) & ~7;
                    if (size == 0) size = 8; // 至少分配8字节

                    local_var_offset += size;
                    unsigned alloca_vreg = isel->getVReg(alloca);
                    // 局部变量使用相对于s0的负向偏移
                    frame_info.alloca_offsets[alloca_vreg] = -local_var_offset;
                }
            }
        }
    }
    
    // 记录仅由AllocaInst分配的局部变量的总大小
    frame_info.locals_size = local_var_offset - 16;

    // 3. 遍历所有机器指令，将伪指令展开为真实指令
    for (auto& mbb : mfunc->getBlocks()) {
        std::vector<std::unique_ptr<MachineInstr>> new_instructions;
        for (auto& instr_ptr : mbb->getInstructions()) {
            RVOpcodes opcode = instr_ptr->getOpcode();

            if (opcode == RVOpcodes::FRAME_LOAD_W || opcode == RVOpcodes::FRAME_LOAD_D || opcode == RVOpcodes::FRAME_LOAD_F) {
                RVOpcodes real_load_op;
                if (opcode == RVOpcodes::FRAME_LOAD_W) real_load_op = RVOpcodes::LW;
                else if (opcode == RVOpcodes::FRAME_LOAD_D) real_load_op = RVOpcodes::LD;
                else real_load_op = RVOpcodes::FLW;

                auto& operands = instr_ptr->getOperands();
                unsigned dest_vreg = static_cast<RegOperand*>(operands[0].get())->getVRegNum();
                unsigned alloca_vreg = static_cast<RegOperand*>(operands[1].get())->getVRegNum();
                int offset = frame_info.alloca_offsets.at(alloca_vreg);
                auto addr_vreg = isel->getNewVReg(Type::getPointerType(Type::getIntType()));

                // 展开为: addi addr_vreg, s0, offset
                auto addi = std::make_unique<MachineInstr>(RVOpcodes::ADDI);
                addi->addOperand(std::make_unique<RegOperand>(addr_vreg));
                addi->addOperand(std::make_unique<RegOperand>(PhysicalReg::S0));
                addi->addOperand(std::make_unique<ImmOperand>(offset));
                new_instructions.push_back(std::move(addi));

                // 展开为: lw/ld/flw dest_vreg, 0(addr_vreg)
                auto load_instr = std::make_unique<MachineInstr>(real_load_op);
                load_instr->addOperand(std::make_unique<RegOperand>(dest_vreg));
                load_instr->addOperand(std::make_unique<MemOperand>(
                    std::make_unique<RegOperand>(addr_vreg),
                    std::make_unique<ImmOperand>(0)));
                new_instructions.push_back(std::move(load_instr));

            } else if (opcode == RVOpcodes::FRAME_STORE_W || opcode == RVOpcodes::FRAME_STORE_D || opcode == RVOpcodes::FRAME_STORE_F) {
                RVOpcodes real_store_op;
                if (opcode == RVOpcodes::FRAME_STORE_W) real_store_op = RVOpcodes::SW;
                else if (opcode == RVOpcodes::FRAME_STORE_D) real_store_op = RVOpcodes::SD;
                else real_store_op = RVOpcodes::FSW;

                auto& operands = instr_ptr->getOperands();
                unsigned src_vreg = static_cast<RegOperand*>(operands[0].get())->getVRegNum();
                unsigned alloca_vreg = static_cast<RegOperand*>(operands[1].get())->getVRegNum();
                int offset = frame_info.alloca_offsets.at(alloca_vreg);
                auto addr_vreg = isel->getNewVReg(Type::getPointerType(Type::getIntType()));
                
                // 展开为: addi addr_vreg, s0, offset
                auto addi = std::make_unique<MachineInstr>(RVOpcodes::ADDI);
                addi->addOperand(std::make_unique<RegOperand>(addr_vreg));
                addi->addOperand(std::make_unique<RegOperand>(PhysicalReg::S0));
                addi->addOperand(std::make_unique<ImmOperand>(offset));
                new_instructions.push_back(std::move(addi));

                // 展开为: sw/sd/fsw src_vreg, 0(addr_vreg)
                auto store_instr = std::make_unique<MachineInstr>(real_store_op);
                store_instr->addOperand(std::make_unique<RegOperand>(src_vreg));
                store_instr->addOperand(std::make_unique<MemOperand>(
                    std::make_unique<RegOperand>(addr_vreg),
                    std::make_unique<ImmOperand>(0)));
                new_instructions.push_back(std::move(store_instr));

            } else if (instr_ptr->getOpcode() == RVOpcodes::FRAME_ADDR) { 
                auto& operands = instr_ptr->getOperands();
                unsigned dest_vreg = static_cast<RegOperand*>(operands[0].get())->getVRegNum();
                unsigned alloca_vreg = static_cast<RegOperand*>(operands[1].get())->getVRegNum();
                int offset = frame_info.alloca_offsets.at(alloca_vreg);

                // 将 `frame_addr rd, rs` 展开为 `addi rd, s0, offset`
                auto addi = std::make_unique<MachineInstr>(RVOpcodes::ADDI);
                addi->addOperand(std::make_unique<RegOperand>(dest_vreg));
                addi->addOperand(std::make_unique<RegOperand>(PhysicalReg::S0));
                addi->addOperand(std::make_unique<ImmOperand>(offset));
                new_instructions.push_back(std::move(addi));

            } else {
                new_instructions.push_back(std::move(instr_ptr));
            }
        }
        mbb->getInstructions() = std::move(new_instructions);
    }
}

} // namespace sysy