[midend]删除前驱后继移除时不存在的检查，phi增加llvm风格接口，重构CFGOpt特别是空块删除的逻辑（待验证）

src/midend/IR.cpp

@@ -569,15 +569,15 @@ void User::replaceOperand(unsigned index, Value *value) {
  * phi相关函数
  */
 
-Value* PhiInst::getvalfromBlk(BasicBlock* blk){
-  refreshB2VMap();
+Value* PhiInst::getvalfromBlk(BasicBlock* blk) const {
+  // refreshB2VMap();
   if( blk2val.find(blk) != blk2val.end()) {
     return blk2val.at(blk);
   }
   return nullptr;
 }
 
-BasicBlock* PhiInst::getBlkfromVal(Value* val){
+BasicBlock* PhiInst::getBlkfromVal(Value* val) const {
   // 返回第一个值对应的基本块
   for(unsigned i = 0; i < vsize; i++) {
     if(getValue(i) == val) {
@@ -591,6 +591,9 @@ void PhiInst::delValue(Value* val){
   //根据value删除对应的基本块和值
   unsigned i = 0;
   BasicBlock* blk = getBlkfromVal(val);
+  if(blk == nullptr) {
+    return; // 如果val没有对应的基本块，直接返回
+  }
   for(i = 0; i < vsize; i++) {
     if(getValue(i) == val) {
       break;
@@ -606,6 +609,9 @@ void PhiInst::delBlk(BasicBlock* blk){
   //根据Blk删除对应的基本块和值
   unsigned i = 0;
   Value* val = getvalfromBlk(blk);
+  if(val == nullptr) {
+    return; // 如果blk没有对应的值，直接返回
+  }
   for(i = 0; i < vsize; i++) {
     if(getBlock(i) == blk) {
       break;
@@ -618,9 +624,12 @@ void PhiInst::delBlk(BasicBlock* blk){
 }
 
 void PhiInst::replaceBlk(BasicBlock* newBlk, unsigned k){
-  refreshB2VMap();
+  // refreshB2VMap();
   BasicBlock* oldBlk = getBlock(k);
   Value* val = blk2val.at(oldBlk);
+  if(newBlk == oldBlk || oldBlk == nullptr) {
+    return; // 如果新旧基本块相同，直接返回
+  }
   // Value* val = blk2val.at(getBlock(k));
   // 替换基本块
   setOperand(2 * k + 1, newBlk);
@@ -630,7 +639,7 @@ void PhiInst::replaceBlk(BasicBlock* newBlk, unsigned k){
 }
 
 void PhiInst::replaceold2new(BasicBlock* oldBlk, BasicBlock* newBlk){
-  refreshB2VMap();
+  // refreshB2VMap();
   Value* val = blk2val.at(oldBlk);
   // 替换基本块
   delBlk(oldBlk);