This is the mail archive of the mailing list for the GCC project.

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: PTR-PLUS merge into the mainline

On 7/5/07, Richard Guenther <> wrote:
On Thu, 5 Jul 2007, Roman Zippel wrote:

> Hi,
> On Thu, 5 Jul 2007, Richard Guenther wrote:
> > If there is anything to fix, then all those variants should produce
> > the same code, not just foo3 and foo4.  So for these cases we should
> > make sure that value-numbering sees them as computing the same value
> > and extend combine to choose the instructions with the least cost.
> >
> > Changing fold isn't a real fix.  It's a workaround for a specific
> > testcase.
> What do you suggest now specifically?
> combine isn't the problem here, at the time we reach RTL this should
> already be done. Your patch only catches specific cases and pessimises
> others.

Well, that's always the nature of any canonicalization.

The following actually makes SCCVN notice that tmp1 == tmp2 in

I posted a general patch to do this for all expressions in one of the bug reports.

I simply didn't do it in the initial sccvn patch  because it's
somewhat memory expensive, and i hadn't measured it's performance.

But as you say, it is certainly possible.

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]