llvm::Argument,llvm::BasicBlock,llvm::Constant,llvm::Instruction这些很重要的类都是它的子类。

llvm::Value有一个llvm::Type*成员和一个use list。后者可以跟踪有哪些其他Value使用了自己，我们可以使用下面的迭代器对它进行访问：

• unsigned use_size() 返回有多少Value使用它
• bool use_empty() 是否没有Value使用它
• use_iterator use_begin() 返回use list的迭代器头
• use_iterator use_end() 返回尾
• User *use_back() 返回use list的最后一个元素

int main() {     Value* val1 = ConstantFP::get(theContext, APFloat(3.2));     if (val1->use_empty()) {         std::cout << "no one use it\n";     }     system("pause");     return 0; }

llvm:Type

前者顾名思义表示一个类型。可以通过Value::getType()获取到这个llvm::Type*,它有一些is*()成员函数可以判断是下面哪种类型：

  enum TypeID {     // PrimitiveTypes - make sure LastPrimitiveTyID stays up to date.     VoidTyID = 0,    ///<  0: type with no size     HalfTyID,        ///<  1: 16-bit floating point type     FloatTyID,       ///<  2: 32-bit floating point type     DoubleTyID,      ///<  3: 64-bit floating point type     X86_FP80TyID,    ///<  4: 80-bit floating point type (X87)     FP128TyID,       ///<  5: 128-bit floating point type (112-bit mantissa)     PPC_FP128TyID,   ///<  6: 128-bit floating point type (two 64-bits, PowerPC)     LabelTyID,       ///<  7: Labels     MetadataTyID,    ///<  8: Metadata     X86_MMXTyID,     ///<  9: MMX vectors (64 bits, X86 specific)     TokenTyID,       ///< 10: Tokens      // Derived types... see DerivedTypes.h file.     // Make sure FirstDerivedTyID stays up to date!     IntegerTyID,     ///< 11: Arbitrary bit width integers     FunctionTyID,    ///< 12: Functions     StructTyID,      ///< 13: Structures     ArrayTyID,       ///< 14: Arrays     PointerTyID,     ///< 15: Pointers     VectorTyID       ///< 16: SIMD 'packed' format, or other vector type   };

比如这样：

int main() {     Value* val1 = ConstantFP::get(theContext, APFloat(3.2));     Type* t = val1->getType();      if (t->isDoubleTy()) {         std::cout << 
                        
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