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基本完成CFG优化（IR修复）

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This commit is contained in:
rain2133
2025-06-23 16:25:52 +08:00
parent 568e9af626
commit 3d233ff199
2 changed files with 363 additions and 36 deletions
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389
src/SysYIROptPre.cpp
View File

@ -17,14 +17,6 @@
namespace sysy {
void SysYOptPre::SysYOptimizateAll() -> void {
SysYDelAfterBr();
SysYBlockMerge();
SysYDelNoPreBLock();
SysYDelEmptyBlock();
SysYAddReturn();
}
/**
* use删除operand,以免扰乱后续分析
* instr: 要删除的指令
@ -61,20 +53,20 @@ void SysYOptPre::SysYDelInstAfterBr() {
Branchiter = instructions.erase(Branchiter);
if (Branch) { // 更新前驱后继关系
auto thelastinst = basicBlock->getInstructions().end();
--thelastinst;
auto thelastinstinst = basicBlock->getInstructions().end();
--thelastinstinst;
auto &Successors = basicBlock->getSuccessors();
for (auto iterSucc = Successors.begin(); iterSucc != Successors.end();) {
(*iterSucc)->removePredecessor(basicBlock.get());
basicBlock->removeSuccessor(*iterSucc);
}
if (thelastinst->get()->isUnconditional()) {
BasicBlock* branchBlock = dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0));
if (thelastinstinst->get()->isUnconditional()) {
BasicBlock* branchBlock = dynamic_cast<BasicBlock *>(thelastinstinst->get()->getOperand(0));
basicBlock->addSuccessor(branchBlock);
branchBlock->addPredecessor(basicBlock.get());
} else if (thelastinst->get()->isConditional()) {
BasicBlock* thenBlock = dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(1));
BasicBlock* elseBlock = dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(2));
} else if (thelastinstinst->get()->isConditional()) {
BasicBlock* thenBlock = dynamic_cast<BasicBlock *>(thelastinstinst->get()->getOperand(1));
BasicBlock* elseBlock = dynamic_cast<BasicBlock *>(thelastinstinst->get()->getOperand(2));
basicBlock->addSuccessor(thenBlock);
basicBlock->addSuccessor(elseBlock);
thenBlock->addPredecessor(basicBlock.get());
@ -90,7 +82,7 @@ void SysYOptPre::SysYBlockMerge() {
auto &functions = pModule->getFunctions(); //std::map<std::string, std::unique_ptr<Function>>
for (auto &function : functions) {
// auto basicBlocks = function.second->getBasicBlocks();
Function* func = function.second.get();
auto &func = function.second;
for (auto blockiter = func->getBasicBlocks().begin();
blockiter != func->getBasicBlocks().end();) {
if (blockiter->get()->getNumSuccessors() == 1) {
@ -104,16 +96,16 @@ void SysYOptPre::SysYBlockMerge() {
auto nextarguments = nextBlock->getArguments();
// 删除br指令
if (block->getNumInstructions() != 0) {
auto thelastinst = block->end();
(--thelastinst);
if (thelastinst->get()->isUnconditional()) {
usedelete(thelastinst->get());
block->getInstructions().erase(thelastinst);
} else if (thelastinst->get()->isConditional()) {
auto thelastinstinst = block->end();
(--thelastinstinst);
if (thelastinstinst->get()->isUnconditional()) {
usedelete(thelastinstinst->get());
block->getInstructions().erase(thelastinstinst);
} else if (thelastinstinst->get()->isConditional()) {
// 如果是条件分支，判断条件是否相同，主要优化相同布尔表达式
if (thelastinst->get()->getOperand(1)->getName() == thelastinst->get()->getOperand(1)->getName()) {
usedelete(thelastinst->get());
block->getInstructions().erase(thelastinst);
if (thelastinstinst->get()->getOperand(1)->getName() == thelastinstinst->get()->getOperand(1)->getName()) {
usedelete(thelastinstinst->get());
block->getInstructions().erase(thelastinstinst);
}
}
}
@ -125,11 +117,12 @@ void SysYOptPre::SysYBlockMerge() {
institer = nextBlock->getInstructions().erase(institer);
}
// 合并参数
// TODO：是否需要去重?
for (auto &argm : nextarguments) {
argm->setParent(block);
block->insertArgument(argm);
}
// // // 改变block 和 next 之间的关系
// 更新前驱后继关系，类似树节点操作
block->removeSuccessor(nextBlock);
nextBlock->removePredecessor(block);
std::list<BasicBlock *> succshoulddel;
@ -142,16 +135,8 @@ void SysYOptPre::SysYBlockMerge() {
nextBlock->removeSuccessor(del);
}
// // // 添加block 和 next 的后继 之间的关系
// block->addSuccessor(nextBlock->getSuccessors()[0]);
// nextBlock->getSuccessors()[0]->addPredecessor(blockiter->get());
// // // 删除next 和 next后继的关系
// nextBlock->getSuccessors()[0]->removePredecessor(nextBlock);
// nextBlock->removeSuccessor(nextBlock->getSuccessors()[0]);
// std::cout << nextBlock->getName() << std::endl;
func->removeBasicBlock(nextBlock);
function.second->removeBasicBlock(nextBlock);
// ++blockiter;
} else {
blockiter++;
}
@ -162,12 +147,344 @@ void SysYOptPre::SysYBlockMerge() {
}
}
// 删除无前驱块，兼容SSA后的处理
void SysYOptPre::SysYDelNoPreBLock() {
auto &functions = pModule->getFunctions(); // std::map<std::string, std::unique_ptr<sysy::Function>>
for (auto &function : functions) {
auto &func = function.second;
for (auto &block : func->getBasicBlocks()) {
block->setreachableFalse();
}
// 对函数基本块做一个拓扑排序，排查不可达基本块
auto entryBlock = func->getEntryBlock();
entryBlock->setreachableTrue();
std::queue<BasicBlock *> blockqueue;
blockqueue.push(entryBlock);
while (!blockqueue.empty()) {
auto block = blockqueue.front();
blockqueue.pop();
for (auto &succ : block->getSuccessors()) {
if (!succ->getreachable()) {
succ->setreachableTrue();
blockqueue.push(succ);
}
}
}
// 删除不可达基本块指令
for (auto blockIter = func->getBasicBlocks().begin(); blockIter != func->getBasicBlocks().end();blockIter++) {
if (!blockIter->get()->getreachable())
for (auto &iterInst : blockIter->get()->getInstructions())
usedelete(iterInst.get());
}
for (auto blockIter = func->getBasicBlocks().begin(); blockIter != func->getBasicBlocks().end();blockIter++) {
if (!blockIter->get()->getreachable()) {
//// 处理phi指令
// 删除不可达基本块的phi指令的操作数
for (auto succblock : blockIter->get()->getSuccessors()) {
int indexphi = 1;
for (auto pred : succblock->getPredecessors()) {
if (pred == blockIter->get()) {
break;
}
indexphi++;
}
for (auto &phiinst : succblock->getInstructions()) {
if (phiinst->getKind() != Instruction::kPhi) {
break;
}
phiinst->removeOperand(indexphi);
}
}
// 删除不可达基本块
func->removeBasicBlock(blockIter->get());
}
}
}
}
void SysyOptimization::SysyDelEmptyBlock() {
auto &functions = pModule->getFunctions();
for (auto &function : functions) {
// 收集不可达基本块
// 这里的不可达基本块是指没有实际指令的基本块
// 当一个基本块没有实际指令例如只有phi指令和一个uncondbr指令时，也会被视作不可达
auto basicBlocks = function.second->getBasicBlocks();
std::map<sysy::BasicBlock *, BasicBlock *> EmptyBlocks;
// 空块儿和后继的基本块的映射
for (auto &basicBlock : basicBlocks) {
if (basicBlock->getNumInstructions() == 0) {
if (basicBlock->getNumSuccessors() == 1) {
EmptyBlocks[basicBlock.get()] = basicBlock->getSuccessors().front();
}
}
else{
// 如果只有phi指令和一个uncondbr。(phi)*(uncondbr)?
// 判断除了最后一个指令之外是不是只有phi指令
bool onlyPhi = true;
for (auto &inst : basicBlock->getInstructions()) {
if (!inst->isPhi() && !inst->isUnconditional()) {
onlyPhi = false;
break;
}
}
if(onlyPhi)
EmptyBlocks[basicBlock.get()] = basicBlock->getSuccessors().front();
}
}
// 更新基本块信息，增加必要指令
for (auto &basicBlock : basicBlocks) {
// 把空块转换成只有跳转指令的不可达块
if (distance(basicBlock->begin(), basicBlock->end()) == 0) {
if (basicBlock->getNumSuccessors() == 0) {
continue;
}
if (basicBlock->getNumSuccessors() > 1) {
assert("");
}
pBuilder->setPosition(basicBlock.get(), basicBlock->end());
pBuilder->createUncondBrInst(basicBlock->getSuccessors()[0], {});
continue;
}
auto thelastinst = basicBlock->getInstructions().end();
--thelastinst;
// 根据br指令传递的后继块信息，跳过空块链
if (thelastinst->get()->getKind()->isUnconditional()) {
BasicBlock* OldBrBlock = dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0));
BasicBlock *thelastBlockOld = nullptr;
// 如果空块链表为多个块
while (EmptyBlocks.find(dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0))) !=
EmptyBlocks.end()) {
thelastBlockOld = dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0));
thelastinst->get()->replaceOperand(0, EmptyBlocks[thelastBlockOld]);
}
basicBlock->removeSuccessor(OldBrBlock);
OldBrBlock->removePredecessor(basicBlock.get());
basicBlock->addSuccessor(dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0)));
dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0))->addPredecessor(basicBlock.get());
if (thelastBlockOld != nullptr) {
int indexphi = 0;
for (auto &pred : dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0))->getPredecessors()) {
if (pred == thelastBlockOld) {
break;
}
indexphi++;
}
// 更新phi指令的操作数
// 移除thelastBlockOld对应的phi操作数
for (auto &InstInNew : dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(1))->getInstructions()) {
if (InstInNew->isPhi()) {
dynamic_cast<PhiInst *>(InstInNew.get())->removeOperand(indexphi + 1);
} else {
break;
}
}
}
} else if (thelastinst->get()->getKind() == Instruction::kCondBr) {
auto OldThenBlock = dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(1));
auto OldElseBlock = dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(2));
BasicBlock *thelastBlockOld = nullptr;
while (EmptyBlocks.find(dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(1))) !=
EmptyBlocks.end()) {
thelastBlockOld = dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(1));
thelastinst->get()->replaceOperand(
1, EmptyBlocks[dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(1))]);
}
basicBlock->removeSuccessor(OldThenBlock);
OldThenBlock->removePredecessor(basicBlock.get());
// 处理 then 和 else 分支合并的情况
if (dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(1)) ==
dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(2))) {
auto thebrBlock = dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(1));
usedelete(thelastinst->get());
thelastinst = basicBlock->getInstructions().erase(thelastinst);
pBuilder->setPosition(basicBlock.get(), basicBlock->end());
pBuilder->createUncondBrInst(thebrBlock, {});
continue;
}
basicBlock->addSuccessor(dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(1)));
dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(1))->addPredecessor(basicBlock.get());
// auto indexInNew = dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0))->getPredecessors().
if (thelastBlockOld != nullptr) {
int index = 0;
for (auto &pred : dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(1))->getPredecessors()) {
if (pred == thelastBlockOld) {
break;
}
index++;
}
for (auto &InstInNew : dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(1))->getInstructions()) {
if (InstInNew->isPhi()) {
dynamic_cast<PhiInst *>(InstInNew.get())->removeOperand(indexphi + 1);
} else {
break;
}
}
}
thelastBlockOld = nullptr;
while (EmptyBlocks.find(dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(2))) !=
EmptyBlocks.end()) {
thelastBlockOld = dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(2));
thelastinst->get()->replaceOperand(
2, EmptyBlocks[dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(2))]);
}
basicBlock->removeSuccessor(OldElseBlock);
OldElseBlock->removePredecessor(basicBlock.get());
// 处理 then 和 else 分支合并的情况
if (dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(1)) ==
dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(2))) {
auto thebrBlock = dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(1));
usedelete(thelastinst->get());
thelastinst = basicBlock->getInstructions().erase(thelastinst);
pBuilder->setPosition(basicBlock.get(), basicBlock->end());
pBuilder->createUncondBrInst(thebrBlock, {});
continue;
}
basicBlock->addSuccessor(dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(2)));
dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(2))->addPredecessor(basicBlock.get());
if (thelastBlockOld != nullptr) {
int index = 0;
for (auto &pred : dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(2))->getPredecessors()) {
if (pred == thelastBlockOld) {
break;
}
index++;
}
for (auto &InstInNew : dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(2))->getInstructions()) {
if (InstInNew->isPhi()) {
dynamic_cast<PhiInst *>(InstInNew.get())->removeOperand(indexphi + 1);
} else {
break;
}
}
}
} else {
if (basicBlock->getNumSuccessors() == 1) {
pBuilder->setPosition(basicBlock.get(), basicBlock->end());
pBuilder->createUncondBrInst(basicBlock->getSuccessors()[0], {});
auto thelastinst = basicBlock->getInstructions().end();
(--thelastinst);
auto OldBrBlock = dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0));
sysy::BasicBlock *thelastBlockOld = nullptr;
while (EmptyBlocks.find(dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0))) !=
EmptyBlocks.end()) {
thelastBlockOld = dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0));
thelastinst->get()->replaceOperand(
0, EmptyBlocks[dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0))]);
}
basicBlock->removeSuccessor(OldBrBlock);
OldBrBlock->removePredecessor(basicBlock.get());
basicBlock->addSuccessor(dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0)));
dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0))->addPredecessor(basicBlock.get());
if (thelastBlockOld != nullptr) {
int index = 0;
for (auto &pred : dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0))->getPredecessors()) {
if (pred == thelastBlockOld) {
break;
}
index++;
}
for (auto &InstInNew : dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0))->getInstructions()) {
if (InstInNew->isPhi()) {
dynamic_cast<PhiInst *>(InstInNew.get())->removeOperand(indexphi + 1);
} else {
break;
}
}
}
}
}
}
for (auto iter = function.second->getBasicBlocks().begin(); iter != function.second->getBasicBlocks().end();) {
if (EmptyBlocks.find(iter->get()) != EmptyBlocks.end()) {
// EntryBlock跳过
if (iter->get() == function.second->getEntryBlock()) {
++iter;
continue;
}
for (auto &iterInst : iter->get()->getInstructions())
usedelete(iterInst.get());
// 删除不可达基本块的phi指令的操作数
for (auto &succ : iter->get()->getSuccessors()) {
int index = 0;
for (auto &pred : succ->getPredecessors()) {
if (pred == iter->get()) {
break;
}
index++;
}
for (auto &instinsucc : succ->getInstructions()) {
if (instinsucc->isPhi()) {
dynamic_cast<PhiInst *>(instinsucc.get())->removeOperand(index);
} else {
break;
}
}
}
function.second->removeBasicBlock((iter++)->get());
} else {
++iter;
}
}
}
}
// 如果函数没有返回指令，则添加一个默认返回指令(主要解决void函数没有返回指令的问题)
void SysYOptPre::SysYAddReturn() {
auto &functions = pModule->getFunctions();
for (auto &function : functions) {
auto &func = function.second;
auto &basicBlocks = func->getBasicBlocks();
for (auto &block : basicBlocks) {
if (block->getNumSuccessors() == 0) {
// 如果基本块没有后继块，则添加一个返回指令
if (block->getNumInstructions() == 0) {
pBuilder->setPosition(block.get(), block->end());
pBuilder->createReturnInst({});
}
auto thelastinst = block->getInstructions().end();
--thelastinst;
if (thelastinst->get()->getKind() != Instruction::kReturn) {
pBuilder->setPosition(block.get(), block->end());
// TODO: 如果int float函数缺少返回值是否需要报错
if (func->getReturnType()->isInt()) {
pBuilder->createReturnInst(ConstantValue::get(0));
} else if (func->getReturnType()->isFloat()) {
pBuilder->createReturnInst(ConstantValue::get(0.0F));
} else {
pBuilder->createReturnInst({});
}
}
}
}
}
}
} // namespace sysy

10
src/include/SysYIROptPre.h
View File

@ -7,6 +7,9 @@ namespace sysy {
// 优化前对SysY IR的预处理，也可以视作部分CFG优化
// 主要包括删除无用指令、合并基本块、删除空块等
// 这些操作可以在SysY IR生成时就完成，但为了简化IR生成过程，
// 这里将其放在SysY IR生成后进行预处理
// 同时兼容phi节点的处理，可以再mem2reg后再次调用优化
class SysYOptPre {
private:
Module *pModule;
@ -15,6 +18,13 @@ class SysYOptPre {
public:
SysYOptPre(Module *pMoudle, IRBuilder *pBuilder) : pModule(pMoudle), pBuilder(pBuilder) {}
void SysYOptimizateAfterIR(){
SysYDelAfterBr();
SysYBlockMerge();
SysYDelNoPreBLock();
SysYDelEmptyBlock();
SysYAddReturn();
}
void SysYDelInstAfterBr(); // 删除br后面的指令
void SysYDelEmptyBlock(); // 空块删除
void SysYDelNoPreBLock(); // 删除无前驱块