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// Peephole.cpp - 保守优化版（仅启用安全规则）
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#include "mir/MIR.h"
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#include <algorithm>
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#include <vector>
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#include <cstdint>
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namespace mir {
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namespace {
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// 判断两个地址操作数是否指向同一内存位置（考虑栈槽和物理寄存器）
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bool SameAddr(const Operand& a, const Operand& b) {
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if (a.GetKind() != b.GetKind()) return false;
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if (a.GetKind() == Operand::Kind::PhysReg)
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return a.GetPhysReg() == b.GetPhysReg();
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if (a.GetKind() == Operand::Kind::FrameIndex)
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return a.GetFrameIndex() == b.GetFrameIndex();
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return false;
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}
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// 规则2：消除死存储（连续两次存储到同一地址，删除第一次）
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// 例如: sw t0, addr; sw t1, addr -> 仅保留第二次存储
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bool EliminateDeadStore(std::vector<MachineInstr>& instrs) {
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bool changed = false;
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for (size_t i = 0; i + 1 < instrs.size(); ) {
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auto& inst1 = instrs[i];
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auto& inst2 = instrs[i+1];
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Opcode op1 = inst1.GetOpcode();
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Opcode op2 = inst2.GetOpcode();
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bool is_store1 = (op1 == Opcode::Store || op1 == Opcode::StoreFloat);
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bool is_store2 = (op2 == Opcode::Store || op2 == Opcode::StoreFloat);
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if (is_store1 && is_store2) {
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const auto& ops1 = inst1.GetOperands();
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const auto& ops2 = inst2.GetOperands();
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// 两个存储操作数至少都有两个操作数 [value, addr]
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if (ops1.size() >= 2 && ops2.size() >= 2 &&
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SameAddr(ops1[1], ops2[1])) {
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// 第一次存储被第二次覆盖，删除第一次
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instrs.erase(instrs.begin() + i);
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changed = true;
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continue; // 重新检查当前位置
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}
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}
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++i;
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}
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return changed;
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}
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} // anonymous namespace
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void RunPeepholeOptimization(MachineFunction& function) {
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bool overallChanged = true;
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while (overallChanged) {
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overallChanged = false;
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for (auto& blockPtr : function.GetBlocks()) {
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auto& instrs = blockPtr->GetInstructions();
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bool changed = false;
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// 启用死存储消除
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changed |= EliminateDeadStore(instrs);
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// changed |= EliminateRedundantStoreLoad(instrs);
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if (changed)
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overallChanged = true;
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}
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}
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}
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} // namespace mir
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