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From: guy@auspex.auspex.com (Guy Harris)
Newsgroups: comp.arch
Subject: Re: SUN procedure inlining(was i860 Dhrystones)
Message-ID: <1387@auspex.auspex.com>
Date: 5 Apr 89 03:34:43 GMT
References: <39388@oliveb.olivetti.com> <15475@winchester.mips.COM> <95013@sun.Eng.Sun.COM> <13641@jumbo.dec.com> <95215@sun.Eng.Sun.COM> <4614@pt.cs.cmu.edu> <1356@auspex.auspex.com> <4641@pt.cs.cmu.edu>
Reply-To: guy@auspex.auspex.com (Guy Harris)
Distribution: na
Organization: Auspex Systems, Santa Clara
Lines: 45

>The original message regarding the -O4 switch was very likely
>an error, as far as I know there is only one -O switch for the SUN3
>family.

There's only one -O switch for the Sun-3 family, just as there's only
one for the Sun-4 family and for the Sun-2 family; however, in SunOS
4.0, the "-O" switch takes an optional optimization level on all three
of those families:

     -O[level] Optimize the object code.  Ignored when either -g,
               -go,  or  -a is used.  On Sun-2 and Sun-3 systems,
               -O with the level omitted is equivalent to -O1; on
               Sun-4  systems,  it  is  equivalent  to  -O2.   on
               Sun386i systems, all levels are  the  same  as  1.
               level is one of:

                    1    Do postpass assembly-level  optimization
                         only.

                    2    Do global  optimization  prior  to  code
                         generation,        including        loop
                         optimizations,   common    subexpression
                         elimination,   copy   propagation,   and
                         automatic register allocation. -O2  does
                         not  optimize  references  to or defini-
                         tions of external or indirect variables.

                    3    Same  as  -O2,  but  optimize  uses  and
                         definitions  of external variables.  -O3
                         does not trace the  effects  of  pointer
                         assignments.  Neither -O3 nor -O4 should
                         be used  when  compiling  either  device
                         drivers,  or programs that modify exter-
                         nal   variables   from   within   signal
                         handlers.

                    4    Same as -O3, but trace  the  effects  of
                         pointer assignments.

>Since the original post seemed to indicate someone had played
>loose with the Dhrystone rules, this seemed like a very possible way it
>could have been done.

The original post seemed to indicate that somebody was confused about
what the Sun compilers did and didn't do.