[optimze]添加基础的除法指令优化，目前只对除以2的幂数生效

src/include/midend/IRBuilder.h

@@ -217,6 +217,9 @@ class IRBuilder {
   BinaryInst * createOrInst(Value *lhs, Value *rhs, const std::string &name = "") {
     return createBinaryInst(Instruction::kOr, Type::getIntType(), lhs, rhs, name);
   }  ///< 创建按位或指令
+  BinaryInst * createSRAInst(Value *lhs, Value *rhs, const std::string &name = "") {
+    return createBinaryInst(Instruction::kSRA, Type::getIntType(), lhs, rhs, name);
+  }  ///< 创建算术右移指令
   CallInst * createCallInst(Function *callee, const std::vector<Value *> &args, const std::string &name = "") {
     std::string newName;
     if (name.empty() && callee->getReturnType() != Type::getVoidType()) {