This intrinsic inserts a USUB8 instruction into the instruction stream generated by the compiler. It enables you to perform four 8-bit unsigned integer subtractions.

The GE bits in the APSR are set according to the results.

unsigned int __usub8(unsigned int val1, unsigned int val2)

Where:

The __usub8 intrinsic returns:

Each bit in APSR.GE is set or cleared for each byte in the return value, depending on the results of the operation. If res is the return value, then:

Example:

unsigned int subtract(unsigned int val1, unsigned int val2)
{
  unsigned int res;

    res = __usub18(val1,val2); /* res[7:0] = val1[7:0] - val2[7:0]
                                  res[15:8] = val1[15:8] - val2[15:8]
                                  res[23:16] = val1[23:16] - val2[23:16]
                                  res[31:24] = val1[31:24] - val2[31:24]
                                */    
}