From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jeffrey A Law <law@cygnus.com>
To: Paul Koning <pkoning@xedia.com>
Cc: egcs@cygnus.com
Subject: Re: stores inside loops 
Date: Thu, 06 Nov 1997 15:17:00 -0000
Message-id: <8742.878858341@hurl.cygnus.com>
References: <9711062254.AA24732@kona.>
X-SW-Source: 1997-11/msg00230.html

  In message < 9711062254.AA24732@kona. >you write:
  > I'm seeing a lack of optimization that surprises me...
  > 
  > Given the following:
  > 
  > extern int a[100], b[100];
  > extern int s;
  > 
  > void foo(void)
  > {
  > 	int i;
  > 	s = 0;
  > 	for (i=0;i<100;i++)
  > 		s += a[i] * b[i];
  > }
  > 
  > I did gcc -O3 -S for {arm, sparc, mips64, x86} and on all of these
  > ended up with code that does the load and store of "s" INSIDE the
  > loop.
  > 
  > Given that s is not declared volatile I had expected that the
  > optimizer would move the load and store outside the loop.  Was that an
  > unreasonable expectation?
Not unreasonable, just not implemented (yet :-).

The new alias code from jfc will be a big help with the time comes to
implement this optimization.


jeff