HP aC++/HP C Programmer's Guide (B3901-90036; A.06.26; September 2011)

and function-scoped statics) will not be read or written through pointers. The default is

+Onoptrs_to_globals.

+O[no]size

While most optimizations reduce code size, the +Osize option suppresses those few

optimizations that significantly increase code size. The +Onosize option enables

code-expanding optimizations.

Use +Osize at all optimization levels. The default is +Onosize.

Advanced +Ooptimization Options

Advanced optimization options provide additional control for special situations.

+O[no]cross_region_addressing

The +O[no]cross_region_addressing option enables [disables] the use of

cross-region addressing. Cross-region addressing is required if a pointer, such as an

array base, points to a different region than the data being addressed due to an offset

that results in a cross-over into another region. Standard conforming applications do not

require the use of cross-region addressing.

The default is +Onocross_region_addressing.

NOTE: Using this option may result in reduced runtime performance.

+O[no]datalayout

The +O[no]datalayout option enables [disables] profile-driven layout of global and

static data items to improve cache memory utilization. This option is currently enabled

if +Oprofile=use (dynamic profile feedback) is specified.

The default, in the absence of +Oprofile=use, is +Onodatalayout.

+O[no]dataprefetch

When +Odataprefetch is enabled, the optimizer inserts instructions within innermost

loops to explicitly prefetch data from memory into the data cache. Data prefetch

instructions are inserted only for data structures referenced within innermost loops using

simple loop varying addresses (that is, in a simple arithmetic progression).

Use this option for applications that have high data cache miss overhead.

+Odataprefetch is equivalent to +Odataprefetch=indirect.

+Onodataprefetch is equivalent to +Odataprefetch=none.

Code Optimizing Options 69