HP UX Fortran Software manual 41

	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.
+O[no]cxlimitedrange	Enables [disables] the use of floating point math in the
	compilation unit.
	The default is +Onocxlimitedrange.
+O[no]cross_region_addressing	Enable [disable] the use of cross-region addressing.
	Cross-region addressing is required if a pointer (such
	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.
+O[no]dataprefetch	+Odataprefetch causes the optimizer to insert
	instructions within innermost loops to explicitly prefetch
	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.
+O[no]dataprefetch=[directindirectnone]	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.
	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.
+O[no]dynopt	Enable [disable] dynamic optimization for the output
	file, if the run-time environment supports this feature.
	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