Conversions

Avoid forcing the compiler to convert numbers between integer and floating-point internal representations. Conversions require several instructions, including some double-precision floating-point arithmetic. For example:

float array[10];
float x = 1.0;
int i;
for (i = 0; i< 9; i++)  {     /* No conversions needed */
     array[i] = array[i]*x;
      x = x + 1.0;
} 
for (i = 0; i< 9; i++)        /* Multiple conversions needed */
   array[i] = array[i]*i;

When you must use mixed-mode arithmetic, code the fixed-point and floating-point arithmetic in separate computations wherever possible.

Writing Optimized Code...
    Overview
    Variables
    Pointers
    Functions
    Function Arguments
    Expressions
    Critical Loops
    Arithmetic Conversions
    Inlined Components