High-level optimizations (HLO) exploit the properties of source code constructs, such as loops and arrays, in the applications developed in high-level programming languages, such as Fortran and C++. They include loop interchange, loop fusion, loop unrolling, loop distribution, unroll-and-jam, blocking, data prefetch, scalar replacement, data layout optimizations and some others. The option that turns on the high-level optimizations is -O3.
| IA-32 and Itanium(TM)-based applications | |
|---|---|
| -O3 | Enable -O2 option plus more aggressive optimizations, for example, loop transformation and prefetching. -O3 optimizes for maximum speed, but may not improve performance for some programs. |
| IA-32 applications | |
| -O3 | In addition, in conjunction with the vectorization options, -ax{M|K|W} and -x{M|K|W}, -O3 causes the compiler to perform more aggressive data dependency analysis than for -O2. This may result in longer compilation times. |