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List:       9fans
Subject:    Re: Why compile.c ?
From:       rob () plan9 ! research ! att ! com
Date:       1994-04-19 17:17:36
Message-ID: 94Apr19.133132edt.293742 () psuvax1 ! cse ! psu ! edu
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Why?  Why do by hand what a machine can do just
as well or better?

The SPARC MMU is inexcusably badly designed.
To make a single kernel that supports all variants
one must either write oodles of ugly assembly code,
with loops that must be unrolled for speed, or generate
code at boot-time tailored to the machine at hand.
We chose the latter approach because it's really
less code to maintain.  I wrote the compiler in just
a couple of hours one afternoon.  It's very easy stuff.

Since some of the code must be generated - for
example, cache line sizes vary from model to model -
what the hell?  Why not generate it all?  Easy, and
susceptible to adaptation as SUN's creative minds
continue to design hardware.

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