Some of the most important points to remember about optimization for the Itanium processor can be summarized as follows:

• As with any other processor, choice of algorithm and adherence to good general optimization principles is the first line of defense.

• Aliasing problems between reads and writes can interfere with software pipelining of loops, so techniques to reduce aliasing are very important.

• Profile-guided optimization can assist the compiler by giving it real world usage and performance information to work with.

• The more code the compiler sees at once, the better it can make optimizations not just within procedures, but (by knowing procedure relationships) between procedures.

• Learning to read the assembly language output of a compiler is very important for understanding how the compiler has chosen to interpret its instructions, and for getting ideas about how to improve performance.

These themes will be discussed at greater length throughout the rest of this chapter.