Specialized optimization techniques

While some optimization techniques are active at advanced optimization levels, certain types of applications can receive a performance benefit even when you apply only basic optimizations.

See the following topics for further information about optimization techniques:

High-order transformation (HOT)
As part of the XL compiler optimization suite, the HOT transformations focus specifically on loops which typically account for the majority of the execution time for most applications. HOT transformations perform in-depth loop analysis to minimize their execution time.
Interprocedural analysis (IPA)
Interprocedural Analysis (IPA) can analyze and optimize your application as a whole, rather than on a file-by-file basis.
Profile-directed feedback
You can use profile-directed feedback (PDF) to tune the performance of your application for a typical usage scenario. The compiler optimizes the application based on an analysis of how often branches are taken and blocks of code are run.
Handling table of contents (TOC) overflow
To handle table of contents (TOC) overflow, you can reduce the number of global symbols, enlarge the TOC access range, or apply interprocedural analysis.
Vector technology
Vector technology is a PowerPC technology for accelerating the performance-driven, high-bandwidth communications and computing applications. You can use the vector technology to get dramatic performance improvement for your applications.
Using compiler reports to diagnose optimization opportunities
You can use the -qlistfmt option to generate a compiler report in XML or HTML format. It provides information about how your program is optimized. You can also use the genhtml utility to convert an existing XML report to HTML format. This information helps you understand your application codes and tune codes for better performance.

Parent topic: Optimizing your applications

Voice your opinion on getting help information

Ask IBM compiler experts a technical question in the IBM XL compilers forum