HP C A.06.05 Reference Manual

Compiling and Running HP C Programs

Pragmas

Chapter 9232

FastCall Pragmas

The compiler directives described in this section are designed to speed up shared library calls.

HP_DEFINED_EXTERNAL Pragma

#pragma HP_DEFINED_EXTERNAL sym1, sym2, ...

The externally deﬁned symbol pragma speciﬁes that the designated symbols are imported

from another load module (program ﬁle or shared library). Note that this pragma currently

works in 32-bit mode only. For 64-bit mode, use the option +Oextern.

HP_LONG_RETURN Pragma

#pragma HP_LONG_RETURN func1, func2, ...

The long return sequence pragma speciﬁes that the named procedures can return directly

across a space, without needing to return through an export stub. The main goal of this

pragma is to eliminate export stubs, and better enable inlining of import stubs and $$dyncall

functionality for indirect calls.

HP_NO_RELOCATION Pragma

#pragma HP_NO_RELOCATION func1, func2, ...

The no parameter/return relocation pragma is used to suppress unnecessary ﬂoating point

argument relocation. When used, the burden is on the caller and callee to have their

argument and their return values agree in which register ﬁles they are passed.

Gather/Scatter Prefetch Pragma

This release supports pragmas for prefetching the cache lines speciﬁed in the pragma.

Syntax

#pragma prefetch <argument>

The behavior of this pragma is similar to the HP_OPT_DATA pragma which prefetches the data

speciﬁed. But the prefetch pragma can access cache lines that are accessed via a vector of

indices.

<argument> can have only one argument per pragma and it must me an array element. For

example, a[i].

The compiler generates instructions to prefetch the cache lines starting from the address of an

argument. The values prefetched must be valid values. Reading off the end of an array may

result in undeﬁned behavior during runtime.