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From: jon@hitachi.uucp (Jon Ryshpan)
Newsgroups: comp.arch,comp.lang.misc
Subject: Re: Compiler Costs
Message-ID: <457@hitachi.uucp>
Date: 10 Jul 90 00:50:05 GMT
References: <1797@apctrc.UUCP> <1990Jul6.161158.1297@zoo.toronto.edu> <1990Jul8.230954.18881@ecn.purdue.edu>
Reply-To: jon@hitachi.UUCP (Jon Ryshpan)
Organization: Hitachi America - Semiconductor & IC Div.
Lines: 26

>>I have a simple question:  Does anyone know what sort of speed-up
>>on gets by going from a good implementation of some algorithm in a
>>third generation language (C, Fortran) and a good optimizing compiler
>>to hand-coded assembly?
...
>							Notice
>that RISC architectures don't have many "funny" instructions, so
>compilers for them can do particularly well against humans....

One of the reasons that it's not so easy to improve on the C compiler
for RISC chips is that they were designed to support good C compilers.
So if what you want to say (what your algorithm requires) is easy to
express in C, you're likely to get an compilation that's hard to improve
on.

Even so, if what you want to say is not easy to express in C, like
"complex number" or "function in a function" or "static variable bound
to a fixed memory location" you may get an object that would benefit
from hand coding.

Jonathan Ryshpan		<...!uunet!hitachi!jon>

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