HP Fortran Programmer's Guide (March 2010)

Compiling and linking
Compiling with the f90 command
Chapter 274
+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.
NOTE This option is deprecated and not supported in future
releases. Use +inline_level.
+inline_level num
This option controls inlining in fortran. The format for num is N[.n], where
num is either an integral value from 0 to 9 or a value with a single decimal
place from 0.0 to 9.0.
For more information on this option, see F90(1) manpage.
+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.