HP Fortran Programmer's Guide (September 2007)

Compiling and linking
Compiling with the f90 command
Chapter 264
The option can change the behavior of programs that perform
exception-handling or that handle asynchronous interrupts.
The default is +Onoentrysched.
+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
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 +O4 and 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 any level of optimization.
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.