AMD 250 manual Example

Software Optimization Guide for AMD64 Processors 25112 Rev. 3.06 September 2005

Example 1

A switch statement like this one, whose case expressions are contiguous integer values, usually provides good performance:

switch (grade)

{

case ‘A’:

...

break; case ‘B’:

...

break; case ‘C’:

...

break; case ‘D’:

...

break; case ‘F’:

...

break;

}

Example 2

Because the case expressions in the following switch statement are not contiguous values, the compiler will likely translate the code into a comparison chain instead of a jump table:

switch (a)

{

case 8:

//Sequence for a==8 break;

case 16:

//Sequence for a==16 break;

...

default:

//Default sequence break;

}

26 C and C++ Source-Level Optimizations Chapter 2