HP aC++/HP C A.06.28 Programmer's Guide Integrity servers (769150-001, March 2014)

tunable will ensure that the compiler does not run out of virtual memory when compiling large files
or functions.
In addition, maxssiz_64bit should be set to 128 MB for very large or complex input files.
(Normally a maxssiz_64bit setting of 64 MB will be sufficient.)
See the kctune man page for more information on how to change kernel tunable parameters.
-O
-O
The -O option invokes the optimizer to perform level 2 optimization. This option is equivalent to
+O2 option.
Example:
This command compiles prog.C and optimizes at level 2:
aCC -O prog.C
+O0
+O0
Use +O0 for fastest compile time or with simple programs. No optimizations are performed.
Example:
This command compiles prog.C and optimizes at level 0:
aCC +O0 prog.C
+O1
+O1
The +O1 option performs level 1 optimization only. This includes branch optimization, dead code
elimination, faster register allocation, instruction scheduling, peephole optimization, and generation
of data prefetch instructions for the benefit of direct (but not indirect) memory accesses. This is the
default optimization level.
Example:
This command compiles prog.C and optimizes at level 1:
aCC +O1 prog.C
+O2
+O2
The +O2 option performs level 2 optimization. This includes level 1 optimizations plus optimizations
performed over entire functions in a single file.
NOTE: Compiling with this optimization setting may require additional memory resources. Refer
to the memory resource discussion above.
Example:
This command compiles prog.C and optimizes at level 2:
aCC +O2 prog.C
+O3
+O3
The +O3 option performs level 3 optimization. This includes level 2 optimizations plus full
optimization across all subprograms within a single file.
54 Command-Line Options