HP Fortran Programmer's Guide (September 2007)

Compiling and linking
Compiling with the f90 command
Chapter 2 69
The default is +Onolibmerrno.
+O[no]loop_block
+O[no]loop_block enables or disables blocking of eligible loops for
improved cache performance. The +Onoloop_block option disables both
automatic and directive-specified loop blocking.
+O[no]loop_transform
+Oloop_transform enables transformation of eligible loops for improved
cache performance. The most important transformation is the interchange
of nested loops to make the inner loop unit stride, resulting in fewer cache
misses. +Onoloop_transform disables transformation of eligible loops. The
default is +Oloop_transform.
+O[no]loop_unroll[= factor ]
+Oloop_unroll turns on loop unrolling. factor is the unroll factor that
controls the code expansion. The default unroll factor is 4; that is, four
copies of the loop body. By experimenting with different factors, you may
improve the performance of your program. This option is only effective at
optimization level 2 or higher.
The default is +Oloop_unroll=4.
+O[no]loop_unroll_jam
+loop_unroll_jam enables loop unrolling and jamming.
+Onoloop_unroll_jam (the default) disables both automatic and
directive-specified unroll and jam. Loop unrolling and jamming increases
register exploitation.
+O[no]moveflop
+Omoveflops allows the optimizer to move conditional floating-point
instructions, enabling other optimizations to occur. This option is only
effective at optimization level 2 or higher.
The behavior of floating-point exception handling may be altered by this
option.
Using +Onomoveflops is recommended if floating-point traps are enabled
and you do not want the behavior of floating-point exceptions to be altered
by the relocation of floating-point instructions, as when your program uses
the ON statement. The default is +Omoveflops.
+O[no]multiprocessor