Manipulating the Contents of a Variable or Register

These functions rotate the contents of a variable to the left:

• int __rlwinm(int, int, int, int) - Rotate left word (immediate), then AND with mask
• int __rlwnm(int, int, int, int) - Rotate left word, then AND with mask
• int __rlwimi(int, int, int, int, int) - Rotate Left word (immediate), then mask insert

The first argument to __rlwimi is overwritten. However, if the first parameter is a local variable allocated to a register, it is both an input and output parameter. For this reason, this intrinsic should always be written to put the result in the same variable as the first parameter as shown here:

ra = __rlwimi( ra, rs, sh, mb, me );
  

You can count the leading zeros in a register using this intrinsic:

int 

  __cntlzw(int);
  

You can use inline assembly for a complete assembly language function, as well as individual assembly language statements.