Re: gcc3 vs 176.gcc

[Joe Buck <jbuck at synopsys dot COM>]

> On Wed, Jan 09, 2002 at 11:30:42AM -0800, Geoff Keating wrote:
> > > Could we change the aliasing check as follows?  First check for
> > > whether two memrefs are accessed off the same register(s); if they
> > > are, we know at once whether the memrefs interfere or not (depending
> > > on the offsets).  Only if the result of this check is indeterminate
> > > do we look at the aliasing info.
> > 
> > Would this slow the compiler?
> 
> Whether it slows the compiler is less of an issue that does
> this work everywhere?

I think that the check happens too late if it is done this way.
Better to detect that the rules are broken at the time of tree->RTL
conversion.  In the 176.gcc case, as soon as we parse

	((int *)rt)[length]

and note that the type of rt is not pointer to (possibly cv-qualified)
int or unsigned, we know already that the rules have been broken,
independent of what the backend is.