126 lines
4.3 KiB
C++
126 lines
4.3 KiB
C++
#include "TailCallOpt.h"
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#include "IR.h"
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#include "IRBuilder.h"
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#include "SysYIROptUtils.h"
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#include <vector>
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// #include <iostream>
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#include <algorithm>
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namespace sysy {
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void *TailCallOpt::ID = (void *)&TailCallOpt::ID;
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void TailCallOpt::getAnalysisUsage(std::set<void *> &analysisDependencies, std::set<void *> &analysisInvalidations) const {
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analysisInvalidations.insert(&DominatorTreeAnalysisPass::ID);
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analysisInvalidations.insert(&LoopAnalysisPass::ID);
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}
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bool TailCallOpt::runOnFunction(Function *F, AnalysisManager &AM) {
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std::vector<CallInst *> tailCallInsts;
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// 遍历函数的所有基本块
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for (auto &bb_ptr : F->getBasicBlocks()) {
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auto BB = bb_ptr.get();
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if (BB->getInstructions().empty()) continue; // 跳过空基本块
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auto term_iter = BB->terminator();
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if (term_iter == BB->getInstructions().end()) continue; // 没有终结指令则跳过
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auto term = (*term_iter).get();
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if (!term || !term->isReturn()) continue; // 不是返回指令则跳过
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auto retInst = static_cast<ReturnInst *>(term);
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Instruction *prevInst = nullptr;
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if (BB->getInstructions().size() > 1) {
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auto it = term_iter;
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--it; // 获取返回指令前的指令
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prevInst = (*it).get();
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}
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if (!prevInst || !prevInst->isCall()) continue; // 前一条不是调用指令则跳过
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auto callInst = static_cast<CallInst *>(prevInst);
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// 检查是否为尾递归调用：被调用函数与当前函数相同且返回值与调用结果匹配
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if (callInst->getCallee() == F) {
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// 对于尾递归，返回值应为调用结果或为 void 类型
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if (retInst->getReturnValue() == callInst ||
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(retInst->getReturnValue() == nullptr && callInst->getType()->isVoid())) {
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tailCallInsts.push_back(callInst);
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}
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}
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}
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if (tailCallInsts.empty()) {
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return false;
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}
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// 创建一个新的入口基本块，作为循环的前置块
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auto original_entry = F->getEntryBlock();
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auto new_entry = F->addBasicBlock("tco.entry." + F->getName());
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auto loop_header = F->addBasicBlock("tco.loop_header." + F->getName());
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// 将原入口块中的所有指令移动到循环头块
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loop_header->getInstructions().splice(loop_header->end(), original_entry->getInstructions());
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original_entry->setName("tco.pre_header");
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// 为函数参数创建 phi 节点
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builder->setPosition(loop_header, loop_header->begin());
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std::vector<PhiInst *> phis;
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auto original_args = F->getArguments();
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for (auto &arg : original_args) {
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auto phi = builder->createPhiInst(arg->getType(), {}, {}, "tco.phi."+arg->getName());
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phis.push_back(phi);
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}
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// 用 phi 节点替换所有原始参数的使用
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for (size_t i = 0; i < original_args.size(); ++i) {
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original_args[i]->replaceAllUsesWith(phis[i]);
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}
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// 设置 phi 节点的输入值
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for (size_t i = 0; i < phis.size(); ++i) {
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phis[i]->addIncoming(original_args[i], new_entry);
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}
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// 连接各个基本块
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builder->setPosition(original_entry, original_entry->end());
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builder->createUncondBrInst(new_entry);
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original_entry->addSuccessor(new_entry);
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builder->setPosition(new_entry, new_entry->end());
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builder->createUncondBrInst(loop_header);
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new_entry->addSuccessor(loop_header);
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loop_header->addPredecessor(new_entry);
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// 处理每一个尾递归调用
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for (auto callInst : tailCallInsts) {
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auto tail_call_block = callInst->getParent();
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// 收集尾递归调用的参数
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auto args_range = callInst->getArguments();
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std::vector<Value*> args;
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std::transform(args_range.begin(), args_range.end(), std::back_inserter(args),
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[](auto& use_ptr){ return use_ptr->getValue(); });
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// 用新的参数值更新 phi 节点
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for (size_t i = 0; i < phis.size(); ++i) {
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phis[i]->addIncoming(args[i], tail_call_block);
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}
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// 移除原有的调用和返回指令
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auto term_iter = tail_call_block->terminator();
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SysYIROptUtils::usedelete(term_iter);
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auto call_iter = tail_call_block->findInstIterator(callInst);
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SysYIROptUtils::usedelete(call_iter);
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// 添加跳转回循环头块的分支指令
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builder->setPosition(tail_call_block, tail_call_block->end());
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builder->createUncondBrInst(loop_header);
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tail_call_block->addSuccessor(loop_header);
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loop_header->addPredecessor(tail_call_block);
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}
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return true;
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}
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} // namespace sysy
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