XL (xlc, xlC, xlf)
Get the latest releases:
GNU Compiler Collection (GCC) [1]
Get the latest release:
Get the latest release: http://releases.llvm.org/
Generate instructions that run on POWER8 -mcpu=power8 (XLC default)
-qarch=pwr8 (XLF default)
-mcpu=power8 -target powerpcle-unknown-linux-gnu
Generate instructions that run on POWER9 -mcpu=power9
-mcpu=power9 -target powerpcle-unknown-linux-gnu
Optimization levels
Disable all optimizations -O0 -qnoopt (default) -O0 (default) -O0 (default)
Optimization levels
-O or -O1
Recommended optimization
(A good balance between run-time performance and compilation time)
Commercial code:
-O3 or -O3 -qipa
Technical computing/analytic:
-O3 or -Ofast
Commercial code:
Technical computing/analytic:
-Ofast -funroll-loops
Additional optimizations
Feedback directed optimization -qpdf1
Interprocedural optimizations -qipa -flto  
OpenMP -qsmp=omp -fopenmp -fopenmp
Loop optimizations -qhot -fpeel-loops

[1] For the latest version of GCC for Linux on Power, plus optimized libraries that can be used with GCC or XL, see the Advance toolchain for Linux on Power pages.

[2] XL also accepts most GNU options