The XL compiler supports several levels of optimization,
with each option level building on the levels below through increasingly
aggressive transformations, and consequently using more machine resources.
Ensure that your application compiles and executes properly at
low optimization levels before trying more aggressive optimizations.
This topic discusses two optimizations levels, listed with complementary
options in the
Basic optimizations table. The table also includes
a column for compiler options that can have a performance benefit
at that optimization level for some applications.
Table 1. Basic
optimizations| Optimization level |
Additional options implied by default |
Complementary options |
Other options with possible benefits |
|---|
| -O0 |
|
|
|
| -O2 |
|
|
- -qmaxmem=-1
- -qhot=level=0
|