HP Fortran Programmer Guide (766160-001, March 2014)

Note the following precautions when using this option:
• All program modules that reference the common
block must be compiled with the
+Ocache_pad_common option.
• Each common block in the program should have
the same layout in all program units within which
it is declared. If the layouts are different, they must
be fully independent—that is, they must not pass
values between them.
The default, +Onocache_pad_common, disables
padding.
Enables [disables] the use of floating point math in the
compilation unit.
The default is +Onocxlimitedrange.
+O[no]cxlimitedrange
Enable [disable] the use of cross-region addressing.
Cross-region addressing is required if a pointer (such
+O[no]cross_region_addressing
as an array base) points to a different region than the
data being addressed. This is usually due to an offset
which results in a cross-over into another region.
Standard-conforming applications do not require the
use of cross-region addressing. The default is
+onocross_region_addressing.
+Odataprefetch causes the optimizer to insert
instructions within innermost loops to explicitly prefetch
+O[no]dataprefetch
data from memory into the data cache. Data prefetch
instructions will be inserted only for data structures
referenced within innermost loops using simple loop
varying addresses—that is, in a simple arithmetic
progression. It is not available for PA-RISC 1.1 targets.
Use this option for applications that have high data
cache miss overhead. The default is
+Onodataprefetch. On HP-UX version 11i and
later, +Odataprefetch is the same as
+Odataprefetch=indirect and
+Onodataprefetch is the same as
+Odataprefetch=none.At +O2and higher, the
default is +Odataprefetch.
Control generation of data prefetch instructions for
data structures referenced within innermost loops. The
defined values for kind are:
direct—enable generation of data prefetch
instructions for the benefit of direct memory accesses,
but not indirect memory accesses.
+O[no]dataprefetch=[direct|indirect|none]
indirect—enable generation of data prefetch
instructions for the benefit of both direct and indirect
memory accesses. This is the default at optimization
levels +O2 and above.
none—disable generation of data prefetch instructions.
This is the default at optimization levels +O1 and
below.
Enable [disable] dynamic optimization for the output
file, if the run-time environment supports this feature.
+O[no]dynopt
Both forms of this option change the default setting,
which allows the run-time environment to enable or
disable dynamic optimization according to
asystem-wide default. This option applies only to
executable files and shared libraries. chatr(1) can
be used to change this setting, including restoration
of the default setting, after the output file has been
created.
Fine-tuning optimization options 41