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From: lee@haddock.UUCP
Newsgroups: net.lang.c
Subject: Re: Re: Re: about void voids (Re: efopen
Message-ID: <86900003@haddock.UUCP>
Date: Sat, 23-Nov-85 18:08:00 EST
Article-I.D.: haddock.86900003
Posted: Sat Nov 23 18:08:00 1985
Date-Received: Mon, 25-Nov-85 07:26:24 EST
References: <382@celerity.UUCP>
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Nf-ID: #R:celerity:-38200:haddock:86900003:000:968
Nf-From: haddock!lee    Nov 23 18:08:00 1985


	I think that "asm" should only be used in functions that meet both
	of the following conditions.

	1) The function is inherently machine-dependent, so that it would
	have to be re-written to port it to a substantially different
	machine.

	2) The alternative to using "asm" is to write it entirely in
	assembly language.

I sometimes find an alternative to condition 1) along the following lines:

	1a) the function is performance sensitive and can be significantly
	improved in performance on a particular architecture by insertion of
	small amounts of inline assembly code.

For example, the operation performed by the IBM 370 "tr" instruction or the
VAX "movtc" instruction can replace a loop in critical sections of otherwise
ordinary C code.

In these cases, of course, the asm() directive containing FOO assembly code
should be embraced in "#if defined(foo)" and the equivalent C code compiled
for architectures for which the asm() directives are not provided.