Re: Compiling for DSP chips (Avi Bloch)
24 Sep 90 12:03:55 GMT

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Newsgroups: comp.compilers
From: (Avi Bloch)
Keywords: C, optimize
Organization: National Semiconductor (IC) Ltd, Israel
References: <> <>
Date: 24 Sep 90 12:03:55 GMT

I realize that I'm a little late on this topic but I just saw the tail end of
this discussion and I thought I'd add what National Semiconductor has to offer
in this field.

National Semiconductor recently announced three micro-processors: the
ns32fx16, ns32cg160 and the ns32gx320. All of these processors have a core of
a general purpose processor with additions for DSP and fax applications.
These additions are accessed using either special instructions or
memory-mapped i/o.

In order to allow the user to access these special instructions from HLL (in
our case - C) we invented a mechanism which we call Application Specific
Instruction Set (ASIS) Support. What this entails is a group of functions and
procedures whose prototypes are supplied in an 'include' file and are
recognized by the compiler. These functions are then inlined by the compiler.
The compiler (including the optimizer) has intimate knowledge on how these
instructions work, e.g., which parameters are changed by the instruction or
in which register each parameter much reside, and it uses this knowledge to
allocate registers and generate code in a most efficient manner. I'm not
saying that it will be as good as if it was written in assembly but in most
cases it's good enough.

I'm willing to add more details for anyone interested.

BTW, if anyone knows of any other compiler that does something similar, I'd be
interested to hear about it.
Avi Bloch
National Semiconductor (Israel)
6 Maskit st. P.O.B. 3007, Herzlia 46104, Israel Tel: (972) 52-522263
[GCC lets you in-line assembler, frequently hidden inside macros, that is
often used to get to features like sin and cos instructions. -John]

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