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Re: [PATCH] PR target/65240, Fix Power{7,8} insn constraint issue with -O3 -ffast-math
- From: Michael Meissner <meissner at linux dot vnet dot ibm dot com>
- To: David Edelsohn <dje dot gcc at gmail dot com>
- Cc: Michael Meissner <meissner at linux dot vnet dot ibm dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Thu, 12 Mar 2015 11:29:53 -0400
- Subject: Re: [PATCH] PR target/65240, Fix Power{7,8} insn constraint issue with -O3 -ffast-math
- Authentication-results: sourceware.org; auth=none
- References: <20150305200638 dot GA3059 at ibm-tiger dot the-meissners dot org> <CAGWvnymp1VoTfGpgxmPwbsWcnTVrZin1-etCAvOHJ0UMaHbzMA at mail dot gmail dot com> <20150311222120 dot GA16631 at ibm-tiger dot the-meissners dot org> <CAGWvny=AQdkVqZ=Ps-AXd-e7Q2pD_k=KS=5QaYqp4jGNcKWdgg at mail dot gmail dot com>
On Wed, Mar 11, 2015 at 08:52:54PM -0400, David Edelsohn wrote:
> On Wed, Mar 11, 2015 at 6:21 PM, Michael Meissner
> <meissner@linux.vnet.ibm.com> wrote:
> > On Wed, Mar 11, 2015 at 01:02:06PM -0400, David Edelsohn wrote:
> >> I am concerned with the create_TOC_reference use for TARGET_TOC. Has
> >> this been tested with big endian -mcmodel=small?
> >
> > Yes, that was a problem. Patch coming up soon. Thanks.
>
> Can you call rs6000_emit_move_directly?
Well, I can, but I would have to have some sort of flag that says after the
split1 pass not to allow FP constants in move (other than 0.0). It is doable,
but it does touch more areas in the rs6000 back end.
I am starting to think that it is just simpler to rip out all of the special
fast math handling of constants, considering the multiply by reciprocal support
has moved to SSA/tree and away from RTL. Did you want me to investigate the
performance implications of removing it now (rather than waiting to GCC 6.0),
or just do the more limited patch that I've been pursuing.
--
Michael Meissner, IBM
IBM, M/S 2506R, 550 King Street, Littleton, MA 01460-6245, USA
email: meissner@linux.vnet.ibm.com, phone: +1 (978) 899-4797