From mboxrd@z Thu Jan  1 00:00:00 1970
From: Joern Rennecke <amylaar@cygnus.co.uk>
To: John Wehle <john@feith.com>
Cc: amylaar@pasanda.cygnus.co.uk, gcc@gcc.gnu.org
Subject: Re: local-alloc update_equiv_regs and moving register initialization
Date: Thu, 14 Sep 2000 16:22:00 -0000
Message-id: <200009142322.AAA30419@phal.cygnus.co.uk>
References: <200009142304.TAA18391@jwlab.FEITH.COM>
X-SW-Source: 2000-09/msg00330.html

> > Because then you might change the semantics of the program.
> 
> That's a good reason, however I'm feeling a bit dense.  How could it
> change the semantics of the program?  If it's safe to change:
> 
>   a = 3;
>   ...
>   c = a + b;
> 
> to
> 
>   ...
>   a = 3;
>   c = a + b;
> 
> when a = 3 and c = a + b are outside a loop, why isn't it safe to make
> the same change when both are inside the same loop?

consider

    if (i)
      c = a + b;
    a = i * 3;