From: Zdenek Dvorak <rakdver@kam.mff.cuni.cz>
To: Richard Guenther <rguenther@suse.de>
Cc: gcc-patches@gcc.gnu.org
Subject: Re: [PATCH] Rewrite store-motion and invariant motion to use an alias-oracle
Date: Wed, 19 Mar 2008 21:20:00 -0000 [thread overview]
Message-ID: <20080319205339.GA4302@kam.mff.cuni.cz> (raw)
In-Reply-To: <Pine.LNX.4.64.0803191634470.4133@zhemvz.fhfr.qr>
Hi,
> > > (maybe there's a better place to do it, but it really needs to be
> > > done on the leaf of expanded expressions).
> >
> > right... still, this seems to be equivalent to transforming
> >
> > unsigned char a, b;
> >
> > (unsigned long) (a + b) to (unsigned long) a + (unsigned long) b
> >
> > which is incorrect when a + b overflows?
>
> Yes. I was assuming the affine combinations are all address arithmetic
> where overflow is undefined or rather does not occur.
no, not necessarily. However, you could call aff_combination_expand
with type = TREE_TYPE (TREE_OPERAND (e, 0)) and make it indicate whether
it expanded some possibly wrapping arithmetics or not, and in case it
did not, cast the result to TREE_TYPE (e).
> Of course unfortunately the ICE that blocks the patch in the first
> place is present with and without that change :/
I will have a look,
Zdenek
next prev parent reply other threads:[~2008-03-19 20:54 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-03-19 14:57 Richard Guenther
2008-03-19 15:08 ` Zdenek Dvorak
2008-03-19 15:14 ` Richard Guenther
2008-03-19 15:38 ` Zdenek Dvorak
2008-03-19 18:21 ` Richard Guenther
2008-03-19 21:20 ` Zdenek Dvorak [this message]
2008-03-21 5:54 ` Zdenek Dvorak
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