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

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.

Usage:

+Odataprefetch=kind

The defined values for kind are:

direct

Enable generation of data prefetch instructions for the benefit of direct

memory accesses, but not indirect memory accesses. This is the default

at optimization level +O1.

indirect

Enables the generation of data prefetch instructions for the benefit of

both direct and indirect memory accesses. This is the default at

optimization levels +O2 and above. It is treated the same as direct at

optimization level +O1.

none

Disables the generation of data prefetch instructions. This is the default

at optimization level +O0.

+O[no]extern

Use the +O[no]extern option at optimization levels 0, 1, 2, 3, or 4. The default is

+Oextern with no name list.

+Oextern is equivalent to -Bextern.

+Onoextern is equivalent to -Bprotected.

76 Command-Line Options