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Re: [PATCH] Fix PR63259: bswap not recognized when finishing with rotation
- From: Jakub Jelinek <jakub at redhat dot com>
- To: "Thomas Preud'homme" <thomas dot preudhomme at arm dot com>
- Cc: gcc-patches at gcc dot gnu dot org, Richard Biener <richard dot guenther at gmail dot com>
- Date: Wed, 8 Oct 2014 09:04:35 +0200
- Subject: Re: [PATCH] Fix PR63259: bswap not recognized when finishing with rotation
- Authentication-results: sourceware.org; auth=none
- References: <000101cfe29b$22541de0$66fc59a0$ at arm dot com> <20141008063843 dot GQ1986 at tucnak dot redhat dot com> <000201cfe2c3$1e3d7d00$5ab87700$ at arm dot com> <000301cfe2c5$08c47080$1a4d5180$ at arm dot com>
- Reply-to: Jakub Jelinek <jakub at redhat dot com>
On Wed, Oct 08, 2014 at 02:56:46PM +0800, Thomas Preud'homme wrote:
> > From: gcc-patches-owner@gcc.gnu.org [mailto:gcc-patches-
> > owner@gcc.gnu.org] On Behalf Of Thomas Preud'homme
> > Sent: Wednesday, October 08, 2014 2:43 PM
> > > Also, perhaps you could short-circuit this if the rotation isn't by constant
>
> Note that do_shift_rotate already check for this. Is it enough?
The question is only about the compile time cost needed through all the
routines find_bswap_or_nop calls before it finds out it can't do anything
with the rotate, the short-circuiting could avoid that. E.g.
find_bswap_or_nop_1 first recurses on the argument etc.
Jakub