HP aC++/HP C A.06.25 Programmer's Guide

This option works like the OPT_LEVEL pragma. The option overrides the pragma for
the specified functions. As with the pragma, you can only lower the level of
optimization; you cannot raise it above the level specified by a basic +Olevel or -O
option. To avoid confusion, it is best to use either this option or the OPT_LEVEL pragma
rather than both.
You can use this option at optimization levels 1, 2, 3, and 4. The default is to optimize
all functions at the level specified by the basic +Olevel or -O option.
Examples:
• The following command optimizes all functions at level 3, except for the functions
myfunc1 and myfunc2, which it optimizes at level 1.
aCC +O3 +O1=myfunc1,myfunc2 funcs.c main.c
• The following command optimizes all functions at level 2, except for the functions
myfunc1 and myfunc2, which it optimizes at level 0.
aCC -O +O0=myfunc1,myfunc2 funcs.c main.c
+O[no]libcalls
+O[no]libcalls
The +O[no]libcalls option is deprecated and may not be supported in future
releases. On Itanium®-based systems, including a system header file will cause the
functions declared therein to be eligible for libcalls transformations, regardless of
the state of +O[no]libcalls.
The default is +Onolibcalls. Use +O[no]libcalls at any optimization level.
See also +Onolibcalls=.
+O[no]loop_block
+O[no]loop_block
Loop blocking is a combination of strip mining and interchange that improves data
cache locality. It is provided primarily to deal with nested loops that manipulate arrays
that are too large to fit into the data cache. Under certain circumstances, loop blocking
allows reuse of these arrays by transforming the loops that manipulate them so that
they manipulate strips of the arrays that fit into the cache.
At optimization levels 3 and 4, using +Oloop_block (the default) allows automatic
loop blocking. Specifying +Onoloop_block disables loop blocking.
+O[no]loop_transform
+O[no]loop_transform
This option transforms [does not transform] eligible loops for improved cache and
other performance. This option can be used at optimization levels 2, 3 and 4.
Code Optimizing Options 81