Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!snorkelwacker.mit.edu!bloom-beacon!eru!hagbard!sunic!mcsun!cernvax!chx400!chx400!sicsun!disuns2!gay_d
From: gay_d@disuns2.epfl.ch (David Gay)
Newsgroups: comp.sys.amiga.programmer
Subject: Re:     Lemmings - a tutorial Part V (last)
Message-ID: <1813@disun4.epfl.ch>
Date: 1 Apr 91 14:16:53 GMT
References: <mykes.0774@amiga0.SF-Bay.ORG> <1991Mar31.003933.1483@mintaka.lcs.mit.edu> <mykes.0926@amiga0.SF-Bay.ORG> <1991Apr1.020748.26863@mintaka.lcs.mit.edu> <mykes.1028@amiga0.SF-Bay.ORG>
Reply-To: gay_d@3/16/89{MAILDOMAIN-.litsun2.ch} (David Gay)
Organization: Ecole Polytechnique Federale de Lausanne
Lines: 47

In article <mykes.1028@amiga0.SF-Bay.ORG> mykes@amiga0.SF-Bay.ORG (Mike Schwartz) writes:
<In article <1991Apr1.020748.26863@mintaka.lcs.mit.edu> rjc@geech.gnu.ai.mit.edu (Ray Cromwell) writes:
<
<>  Obviously you have no idea of how advanced today's optimizing compilers
<>are.  The code you stepped through must have been produced by some
<>1970's MetaComco compiler or something. But FYI, most of todays compilers
<>can pass arguements in registers, allocate memory without stack, eliminate
<>the frame registers, and even do all the non-obvious tricks of sign extension,
<>etc. Check out the code I've included at the end compiled by GCC.
<>
<>The following was compiled with GCC -O -fstrength-reduce -fomit-frame-register
<>I don't have SAS C on the Amiga, but I'm sure it produces simular results.
<>
<>/* test.c */
<>
<>char buf[20];
<>main()
<>{
<>  char *d=(char *)&buf;
<>  const char *s="This is a test\n";
<>  while(*s) { *d++=*s++; }
<>}

[Code deleted to satisfy inews, sorry]

<NO COMPARISON DUDE!  GCC makes 3 totally wasted instructions, and one of
<them is inside your loop. 

0 wasted instructions, see below.

[Stupid statistics deleted]

I wonder what makes you think that move.b (a0)+,(a1)+ is equivalent to
move.b (a0)+,(a1)+ / tst.b (a0) ? Your routine *doesn't* do the same thing
as the C code, you're copying a NULL character extra. 

So we have an optimised C version and an optimised buggy assembler version. 
Which would you choose ?

<Just think, the OS ROM routines are written in 'C' and compiled with
<a lesser compiler than gcc (5 years ago).

Just think, if the OS had been in assembler maybe it would have been released
next year ...

David Gay
gay_d@disuns2.epfl.ch