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From: bhoughto@bishop.intel.com (Blair P. Houghton)
Newsgroups: comp.lang.c
Subject: Re: low level optimization
Summary: Good bit of bathos at the end of this one.
Message-ID: <3904@inews.intel.com>
Date: 19 Apr 91 03:44:10 GMT
References: <21660@lanl.gov> <1991Apr17.225944.15261@zoo.toronto.edu> <21812@lanl.gov>
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In article <21812@lanl.gov> jlg@cochiti.lanl.gov (Jim Giles) writes:
>In article <1991Apr17.225944.15261@zoo.toronto.edu>, henry@zoo.toronto.edu (Henry Spencer) writes:
>|> [...] You do interprocedural analysis across all source files
>|>supplied to a single invocation of the compiler,  [...]
>
>And, if you subsequently change _some_ of those source files?  What 
>then?  Under this model, you'd have to recompile _all_ the others 
>that were originally compiled together.  This violates one of the 
>principle reasons to have separate compilation to begin with - the 
>elimination of the needto recompile most of your code every time 
>you change a piece of it.

ANSI X3.159-1989, sec. 2.1.2.3, p. 8, l. 30:
"...issues of optimization are irrelevant."

The only reason you need to recompile (in this situation,
from the information given) is to provide the compiler
enough information to optimize a certain subset of the
syntax.  If you want optimizations of this sort, you must:

    (a) use a compiler which provides this optimization;
    (b) write a makefile that indicates the dependencies
	inherent in this optimization; and,
    (c) run make(1) instead of cc(1).

Neither are any of these things specified by the standard,
nor are any of them prohibited to be used in concert with a
conforming implementation of the C language.

Basically, if you want to do something outside the realm of
all sensibility, you may have to hold its hand.

				--Blair
				  "And you'll _still_ spend less time each
				   day recompiling source files than you do
				   shaking your penis dry at the urinal."