C register usage - (nf)

[johnl at ima.UUCP]

#R:ulysses:-55500:ima:15900011:000:872
ima!johnl    Aug 19 17:42:00 1983

***** ima:general / ism780!jim /  1:47 pm  Aug 19, 1983
The 32v people who violated DEC's calling conventions and neglected
to save r2-r5 in C routines, presumably because they are used as temporaries
by structure copies and complex expressions, made a mistake.
These registers now must be saved upon each interrupt which calls or leads to
the call of a C routine, which is very costly, while the actual occurrence of
uses of r2-r5 is minimal.

I think the Bell VAX assembler language manual was pulled because the
design and implementation were too embarrassing.  The SysV assembler
is a different program, but Bell still hasn't gotten around to providing
a manual.  It is more than a little ironic that someone at MH should be
asking the net about history of Bell documentation practices.

Jim Balter (decvax!yale!ima!jim), Interactive Systems Corp

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