Impulse has just published an Application Note describing how to integrate custom hardware libraries with the Impulse C compiler. The Application Note (IATAPP108_LIBRARIES) is available for download here:

http://www.impulsec.com/application_notes.htm

From the introduction:

QUOTE
The Impulse C compiler allows the use of customized platform- or application-specific hardware components, either through the use of Platform Support Packages or through explicitly referenced hardware primitive functions.

Custom hardware components may be required for a number of reasons. For example, a complex calculation may benefit from the use of a hand-crafted, low-level hardware primitive, or a custom hardware component related to system I/O may be required. Such components can be integrated into Impulse C at the language level using an open interface to the Impulse C compiler, or via a Platform Support Package library reference. Whether your goal is to redefine the division operator, add a new math library function, or provide an entire floating-point library for a new Platform Support Package, it’s possible to customize the C-to-HDL translation and optimization capabilities of Impulse C for your target hardware platform.

This document describes how custom hardware components can be specified and used via the Platform Support Package interface.