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
|