/* Code blocks, which in proper compiler terminology are superblocks
   (single entry, multiple exit code sequences) contain:
　　【与Intel Pin中的概念trace是相似的】

   - A table giving a type for each temp (the "type environment")
   - An expandable array of statements
   - An expression of type 32 or 64 bits, depending on the
     guest‘s word size, indicating the next destination if the block 
     executes all the way to the end, without a side exit
   - An indication of any special actions (JumpKind) needed
     for this final jump.
   
   "IRSB" stands for "IR Super Block".
*/
typedef
   struct {
      IRTypeEnv* tyenv;
      IRStmt**   stmts;
      Int        stmts_size;
      Int        stmts_used;
      IRExpr*    next;
      IRJumpKind jumpkind;
   }
   IRSB;

 Each IRSB contains three things:
   - a type environment, which indicates the type of each temporary
     value present in the IRSB
   - a list of statements, which represent code
   - a jump that exits from the end the IRSB

Statements (type ‘IRStmt‘) represent operations with side-effects,
   eg.  guest register writes, stores, and assignments to temporaries.
   Expressions (type ‘IRExpr‘) represent operations without
   side-effects, eg. arithmetic operations, loads, constants.
   Expressions can contain sub-expressions, forming expression trees,
   eg. (3 + (4 * load(addr1)).

在代表guest state的缓存中的offset

代表操作数长度的type