HP UX Fortran Software +Onoentrysched, +Onofailsafe, +Ofaster, +Onofenvaccess, +Onofastaccess

+O[no]entrysched	+Oentrysched allows the optimizer to perform
	instruction scheduling on a subprogram’s entry and
	exit code sequences. This option is only effective at
	optimization level 1 or higher.
	The option can change the behavior of programs that
	perform exception-handling or that handle
	asynchronous interrupts.
	The default is +Onoentrysched.
	NOTE: This option is valid only on the PA-RISC
	systems.
+O[no]failsafe	Enable [disable] failsafe optimization. When a
	compilation fails at the current optimization level,
	+Ofailsafe will automatically restart the
	compilation at +O2(for specific high level optimizer
	errors +O3/+O4) or +O1 for Itanium® processor family
	architecture and +O0 for PA-RISC architecture. The
	default is +Ofailsafe.
+Ofast	Select a combination of compilation options for
	optimum execution speed of the compiled program.
	Those options include: +O2,
	+Olibcalls+Onolimit, +Ofltacc=relaxed,
	and +FPD. +Ofast also causes the +pi4M, +pd4M
	options to be passed to the linker. In addition to these
	options, on the Itanium processor family architecture,
	+DSnative instruction scheduling is selected and
	+mergeseg is also passed to the linker.
+Ofaster	Selects the +Ofast option at optimization level +O3
	for PA-RISC based architectures. For Itanium processor
	family architectures, +Ofaster runs at +O4and implies
	-ipo.
+O[no]fenvaccess	Inform the compiler that the program accesses [does
	not access] the floating point environment to test flags
	or run under non-default modes. If it knows that a
	program does not access the floating point
	environment, the compiler is allowed to perform certain
	optimizations that it otherwise may not perform, such
	as global common subexpression elimination, code
	motion, or constant folding.
	The default is +Onofenvaccess.
+O[no]fastaccess	+Ofastaccess improves execution time by speeding
	up access to global data items. You can use this option
	at optimization level 1 or higher. Note that the
	+Ofastaccess option may increase link time. The
	default is +Onofastaccess at optimization levels 1,
	2, and 3; and +Ofastaccess at optimization level
	4.
	NOTE: This option is valid only on
+O[no]fltacc	+Onofltacc enables optimizations that follow the
	rules of algebra but may change the order of
	expression evaluation. For example, if a, b, and c are
	floating-point variables, the expressions (a + b) +
	c and a + (b + c)may give slightly different results
	due to roundoff.
	The +Onofltacc option also enables the fusion of
	adjacent multiply and add operations—resulting in
	Fused Multiply-Add (FMA). (At optimization level 2 or
	higher, FMA occurs by default.) FMA improves
	performance but occasionally produces results that
	may differ in accuracy from results produced by code
	where fusion has not occurred. In general, the
	differences are slight.

42 Compiling and linking