Path: utzoo!attcan!uunet!lll-winken!unixhub!shelby!portia.stanford.edu!dhinds
From: dhinds@portia.stanford.edu (David Hinds)
Newsgroups: comp.sys.sgi
Subject: Optimization options in Irix 3.3 Fortran and C
Message-ID: <1990Sep26.185742.7454@portia.Stanford.EDU>
Date: 26 Sep 90 18:57:42 GMT
Sender: dhinds@portia.Stanford.EDU (David Hinds)
Organization: AIR, Stanford University
Lines: 17

On the last page of the 3.3 fortran-77 release notes, there is a paragraph
about optimization of multiprocessed fortran code.  It says the combination
of -o3 and -mp will disable the "no parameter aliasing" optimization, but
that this can be re-enabled as an option to "uopt".  My first question is,
why is this?  What is special about multiprocessed fortran that changes the
way parameter aliasing can be handled?  (Aliasing is not allowed in the
Fortran standard, anyway).
My second question is, is this optimization flag available for code in other
languages?  Can I link a pure C program with a "-Wo,-noPalias" option if
my code does not use aliasing, or does the standard library use aliasing
that will screw things up?  Because aliasing in C is a significant barrier
to optimization, yet rarely used, it seems that this would be a useful
trick.  Are there any other options to "uopt" that we should know about?
I can't find a manual page for it anywhere.

 -David Hinds
  dhinds@cb-iris.stanford.edu