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Path: utzoo!watmath!operators
From: operators@watmath.UUCP (M.F.C.F. Operators)
Newsgroups: net.arch,net.unix
Subject: Re: timing study of uVAX II instructions
Message-ID: <2422@watmath.UUCP>
Date: Sat, 3-May-86 19:48:22 EDT
Article-I.D.: watmath.2422
Posted: Sat May  3 19:48:22 1986
Date-Received: Sun, 4-May-86 06:17:40 EDT
References: <90@wheaton> <1730@mit-eddie.MIT.EDU>
Reply-To: operators@watmath.UUCP (Alan T. Bowler [SDG])
Organization: U of Waterloo, Ontario
Lines: 22
Xref: watmath net.arch:3200 net.unix:7763
Summary: 

In article <1730@mit-eddie.MIT.EDU> jbs@mit-eddie.UUCP (Jeff Siegal) writes:
>Of course, this has been said before, but the time for the call
>instructions also gives some idea of how useful it is to have a
>compiler which:
>
>1) Expands function calls inline when appropriate.
>
>2) Uses a faster, but less general, way to get to a function when
>possible (usually only for "static" functions).
>
or 3) Have a compiler designers spent a significant amount of time
     thinking about and designing a call convention call convention
     that is fast and flexible.

It has been observed a number of times that the manufacturer suggested
call convention is seldom even close to being optimal for the machine.
Similarly, the ones used by most C compilers are simply quick adaptations
from the one used on the last machine the compiler implementor saw.
I have often wondered how much the "RISC" performance comes simply
from the fact that registers were used to pass arguments, instead
of being blindly having garbage values "saved" and restored on every call.