HP Fortran Programmer Guide HP-UX 11i v1, HP-UX 11i v2, and HP-UX 11i v3 (B3908-90032,December 2012)

levels +O1and +O2. It is enabled by default when +O4 or+O faster are
used.
+kgenerates code for programs that reference a very large number of
shared data items. The linker will issue a diagnostic message in the rare
+k
case when this option is needed. By default, the compiler generates
short-displacement code sequences for programs that reference global
data in shared libraries. For nearly all programs, this is sufficient.
NOTE: +koption is not valid on HP Itanium®-based systems.
+nocheckufdisables the OPEN statement error check for opening text files with
ACCESS=”sequential”, FORM=”unformatted”. This option is useful only when
+nocheckuf
BUFFERIN/BUFFEROUT statements will be used to access the opened unit. The main program
must be compiled with this option for it to have any effect, and all OPEN statements will then
skip this error check.
Disables the passing of libraries to the linker. This is useful when symbols are resolved at runtime
through dynamically loaded libraries.
+nolibs
Do not pad shared common blocks to a multiple of 8 bytes. This option is useful when sharing
shared common blocks betweenf77programs and f90-generated programs. All source files
referencing the same shared common block must be compiled with the same setting of this flag.
+nopadsharedcommon
-Oinvokes the optimizer, where nis the level of optimization, 0 - 4. The default is optimization
level 2.
-O[n]
+Oinvokes the optimizer, where nis the level of optimization, 0 - 4. The -goption is compatible
with the +O0,+O1, and +O2options.
+On
Table 2-6 lists and describes the different levels of optimization.
NOTE: See the Parallel Programming Guide for HP-UX Systemsfor a detailed description of
optimization levels and methods.
+O[no]options enable or disable specific optimizations or classes of optimizations
(for example, optimizations that affect compilation time). For detailed information
about +O[no]optimization, see “Using optimization options” on page 60.
+O[no]optimization
Table 15 Levels of optimization
OptimizationsLevel
Local optimizations, including constant folding and partial evaluation of test conditions.0
Peephole optimizations, including:1
• Basic block optimizations
• Branch optimizations
• Instruction scheduling
Optimizations performed at level 1, plus the following:2
• Coloring register allocation
• Induction variables and strength reduction
• Common subexpression elimination
• Loop invariant code motion
• Store/copy optimization
• Unused definition elimination
• Dataflow analysis
• Software pipelining
30 Compiling and linking