On 6/29/07, Roman Zippel <[EMAIL PROTECTED]> wrote:
Hi,
On Thu, 28 Jun 2007, [EMAIL PROTECTED] wrote:
> Roman Zippel <[EMAIL PROTECTED]> wrote on 06/28/2007 07:54:43 PM:
>
> > Hi,
> > Notice that it generates the (i + 1) * 4 instead of (i * 4) + 4 as with
> > the other cases. While I tried to debug this I narrowed it down to the
> > changes in fold_binary(), but I don't really know how to fix this, so
> > I could use some help here.
>
> The main thing is that this is really PR 32120. The problem is only
> related to the
> merge because of the way fold_binary works.
I'm not sure that's related, what's happening in my example is that the
call to fold_plusminus_mult_expr() defeats the optimization attempted in
pointer_int_sum(). If I use the patch below to restrict the condition, my
problem is fixed, but PR32120 is unchanged.
Actually if I compare the final_cleanup dump of PR32120 with the output
from gcc 4.1, they are basically identical.
The code to fold_binary was added by:
r107218 | rguenth | 2005-11-19 03:29:10 -0800 (Sat, 19 Nov 2005) | 9 lines
2005-11-19 Richard Guenther <[EMAIL PROTECTED]>
PR middle-end/23294
* fold-const.c (fold_plusminus_mult_expr): New function.
(fold_binary): Use to canonicalize PLUS_EXPR and MINUS_EXPR
cases, remove now unnecessary code.
* gcc.dg/tree-ssa/pr23294.c: New testcase.
And it looks like it was doing this transformation this way on purpose.
Now as I mentioned before the way this should be done is using PRE/FRE
to catch the redudent multiplication.
-- Pinski
