157 lines
7.3 KiB
C++
157 lines
7.3 KiB
C++
#include "EliminateFrameIndices.h"
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#include "RISCv64ISel.h"
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#include <cassert>
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namespace sysy {
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unsigned EliminateFrameIndicesPass::getTypeSizeInBytes(Type* type) {
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if (!type) {
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assert(false && "Cannot get size of a null type.");
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return 0;
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}
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switch (type->getKind()) {
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case Type::kInt:
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case Type::kFloat:
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return 4;
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case Type::kPointer:
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return 8;
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case Type::kArray: {
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auto arrayType = type->as<ArrayType>();
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return arrayType->getNumElements() * getTypeSizeInBytes(arrayType->getElementType());
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}
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default:
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assert(false && "Unsupported type for size calculation.");
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return 0;
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}
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}
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void EliminateFrameIndicesPass::runOnMachineFunction(MachineFunction* mfunc) {
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StackFrameInfo& frame_info = mfunc->getFrameInfo();
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Function* F = mfunc->getFunc();
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RISCv64ISel* isel = mfunc->getISel();
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// 1. 为栈传递的参数计算偏移量
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if (F) {
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int arg_idx = 0;
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for (Argument* arg : F->getArguments()) {
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// 只关心第8个索引及之后的参数 (即第9个参数开始)
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if (arg_idx >= 8) {
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// 第一个栈参数(idx=8)在0(s0), 第二个(idx=9)在8(s0)
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int offset = (arg_idx - 8) * 8;
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unsigned vreg = isel->getVReg(arg);
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frame_info.alloca_offsets[vreg] = offset;
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}
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arg_idx++;
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}
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}
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// 2. 为局部变量分配空间，起始点在 [ra, s0] (16字节) 之后
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int local_var_offset = 16;
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// 处理局部变量 (AllocaInst)
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if(F) { // 确保函数指针有效
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for (auto& bb : F->getBasicBlocks()) {
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for (auto& inst : bb->getInstructions()) {
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if (auto alloca = dynamic_cast<AllocaInst*>(inst.get())) {
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Type* allocated_type = alloca->getType()->as<PointerType>()->getBaseType();
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int size = getTypeSizeInBytes(allocated_type);
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// RISC-V要求栈地址8字节对齐
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size = (size + 7) & ~7;
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if (size == 0) size = 8; // 至少分配8字节
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local_var_offset += size;
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unsigned alloca_vreg = isel->getVReg(alloca);
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// 局部变量使用相对于s0的负向偏移
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frame_info.alloca_offsets[alloca_vreg] = -local_var_offset;
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}
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}
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}
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}
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// 记录仅由AllocaInst分配的局部变量的总大小
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frame_info.locals_size = local_var_offset - 16;
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// 3. 遍历所有机器指令，将伪指令展开为真实指令
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for (auto& mbb : mfunc->getBlocks()) {
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std::vector<std::unique_ptr<MachineInstr>> new_instructions;
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for (auto& instr_ptr : mbb->getInstructions()) {
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RVOpcodes opcode = instr_ptr->getOpcode();
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if (opcode == RVOpcodes::FRAME_LOAD_W || opcode == RVOpcodes::FRAME_LOAD_D || opcode == RVOpcodes::FRAME_LOAD_F) {
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RVOpcodes real_load_op;
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if (opcode == RVOpcodes::FRAME_LOAD_W) real_load_op = RVOpcodes::LW;
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else if (opcode == RVOpcodes::FRAME_LOAD_D) real_load_op = RVOpcodes::LD;
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else real_load_op = RVOpcodes::FLW;
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auto& operands = instr_ptr->getOperands();
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unsigned dest_vreg = static_cast<RegOperand*>(operands[0].get())->getVRegNum();
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unsigned alloca_vreg = static_cast<RegOperand*>(operands[1].get())->getVRegNum();
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int offset = frame_info.alloca_offsets.at(alloca_vreg);
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auto addr_vreg = isel->getNewVReg(Type::getPointerType(Type::getIntType()));
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// 展开为: addi addr_vreg, s0, offset
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auto addi = std::make_unique<MachineInstr>(RVOpcodes::ADDI);
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addi->addOperand(std::make_unique<RegOperand>(addr_vreg));
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addi->addOperand(std::make_unique<RegOperand>(PhysicalReg::S0));
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addi->addOperand(std::make_unique<ImmOperand>(offset));
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new_instructions.push_back(std::move(addi));
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// 展开为: lw/ld/flw dest_vreg, 0(addr_vreg)
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auto load_instr = std::make_unique<MachineInstr>(real_load_op);
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load_instr->addOperand(std::make_unique<RegOperand>(dest_vreg));
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load_instr->addOperand(std::make_unique<MemOperand>(
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std::make_unique<RegOperand>(addr_vreg),
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std::make_unique<ImmOperand>(0)));
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new_instructions.push_back(std::move(load_instr));
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} else if (opcode == RVOpcodes::FRAME_STORE_W || opcode == RVOpcodes::FRAME_STORE_D || opcode == RVOpcodes::FRAME_STORE_F) {
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RVOpcodes real_store_op;
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if (opcode == RVOpcodes::FRAME_STORE_W) real_store_op = RVOpcodes::SW;
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else if (opcode == RVOpcodes::FRAME_STORE_D) real_store_op = RVOpcodes::SD;
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else real_store_op = RVOpcodes::FSW;
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auto& operands = instr_ptr->getOperands();
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unsigned src_vreg = static_cast<RegOperand*>(operands[0].get())->getVRegNum();
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unsigned alloca_vreg = static_cast<RegOperand*>(operands[1].get())->getVRegNum();
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int offset = frame_info.alloca_offsets.at(alloca_vreg);
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auto addr_vreg = isel->getNewVReg(Type::getPointerType(Type::getIntType()));
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// 展开为: addi addr_vreg, s0, offset
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auto addi = std::make_unique<MachineInstr>(RVOpcodes::ADDI);
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addi->addOperand(std::make_unique<RegOperand>(addr_vreg));
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addi->addOperand(std::make_unique<RegOperand>(PhysicalReg::S0));
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addi->addOperand(std::make_unique<ImmOperand>(offset));
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new_instructions.push_back(std::move(addi));
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// 展开为: sw/sd/fsw src_vreg, 0(addr_vreg)
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auto store_instr = std::make_unique<MachineInstr>(real_store_op);
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store_instr->addOperand(std::make_unique<RegOperand>(src_vreg));
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store_instr->addOperand(std::make_unique<MemOperand>(
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std::make_unique<RegOperand>(addr_vreg),
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std::make_unique<ImmOperand>(0)));
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new_instructions.push_back(std::move(store_instr));
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} else if (instr_ptr->getOpcode() == RVOpcodes::FRAME_ADDR) {
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auto& operands = instr_ptr->getOperands();
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unsigned dest_vreg = static_cast<RegOperand*>(operands[0].get())->getVRegNum();
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unsigned alloca_vreg = static_cast<RegOperand*>(operands[1].get())->getVRegNum();
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int offset = frame_info.alloca_offsets.at(alloca_vreg);
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// 将 `frame_addr rd, rs` 展开为 `addi rd, s0, offset`
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auto addi = std::make_unique<MachineInstr>(RVOpcodes::ADDI);
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addi->addOperand(std::make_unique<RegOperand>(dest_vreg));
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addi->addOperand(std::make_unique<RegOperand>(PhysicalReg::S0));
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addi->addOperand(std::make_unique<ImmOperand>(offset));
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new_instructions.push_back(std::move(addi));
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} else {
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new_instructions.push_back(std::move(instr_ptr));
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}
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}
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mbb->getInstructions() = std::move(new_instructions);
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}
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}
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} // namespace sysy
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