Using the compiler optimization options

The -O3 compiler option provides a high level of optimization and automatically sets other compiler options. For example, the -qfloat=rsqrt and -qmaxmem=1 options are set by default with -O3, unless -qstrict is specified. Specifying -O3 implies -qhot=level=0, unless you explicitly specify -qhot or -qhot=level=1 option.

The -qhot=simd option enables SIMD vectorization of loops, and is enabled by default if you use -O4, -O5, or -qhot .

For more information on optimization options, see Optimizing your applications in the XL C/C++ Advanced Edition V8.0 for Linux Programming Guide and Optimizing XL compiler applications in the XL Fortran Advanced Edition V10.1 for Linux Optimization and Programming Guide.