HP C/aC++ for PA-RISC Software manual Using +DS to Specify Instruction Scheduling

Tune to run reasonably well on multiple implementations. As old implementation become less important and new implementations are added, the behavior with this value will change accordingly.

Examples:

The following command generates code for the 64-bit data model:

aCC +DD64 app.C

The following command generates code for the 32-bit data model:

aCC app.C

+DSmodel

The +DSmodel option performs instruction scheduling for a particular implementation of the Itanium®-based architecture.

model can be one of the following values. blended

itanium	Tune for the Itanium® processor.
itanium2	Tune for the Itanium2® processor.
mckinley	See itanium2® .
montecito	Tune for the Montecito® processor.
poulson	Tune for the Poulson® processor.
native	Tune for the processor on which the compiler is running.

The default is blended. Object code with scheduling tuned for a particular model will execute on other HP-UX systems, although possibly less efficiently.

Using +DS to Specify Instruction Scheduling

Instruction scheduling is different on different implementations of Itanium®-based architectures. You can improve performance on a particular model or processor of the HP-UX system by requesting the compiler to use instruction scheduling tuned to that particular model or processor. Using scheduling for one model or processor does not prevent your program from executing on another model or processor.

If you plan to run your program on the same system where you are compiling, you do not need to use the +DS option. The compiler generates code tuned for your system.

If you plan to run your program on a particular model of the HP-UX system, and that model is different from the one where you compile your program, use +DSmodel with either the model number of the target system or the processor name of the target system.

Compiling in Networked Environments

When compiles are performed using diskless workstations or NFS-mounted file systems, it is important that the default code generation and scheduling are based on the local host processor. The system model numbers of the hosts where the source or object files reside do not affect the default code generation and scheduling.

-S

The -Soption compiles a program and logs the assembly language output in a corresponding file with a .s suffix. The -Soption is only for displaying the assembler code. The generated code is not intended to be used as input to the assembler (as).

Example:

Options to Control Code Generation 33