[PATCH] [LLVMdev] More FMA folding opportunities

Tue Jan 13 07:11:20 PST 2015

Commit r225795.

Olivier

From:	Hal Finkel <hfinkel at anl.gov>
To:	Olivier H Sallenave/Watson/IBM at IBMUS
Cc:	<llvm-commits at cs.uiuc.edu>, Owen Anderson <resistor at mac.com>
Date:	01/13/2015 03:55 AM
Subject:	Re: [PATCH] [LLVMdev] More FMA folding opportunities

----- Original Message -----
> From: "Olivier H Sallenave" <ohsallen at us.ibm.com>
> To: "Owen Anderson" <resistor at mac.com>
> Cc: "Hal Finkel" <hfinkel at anl.gov>, llvm-commits at cs.uiuc.edu
> Sent: Monday, January 12, 2015 2:01:28 PM
> Subject: Re: [PATCH] [LLVMdev] More FMA folding opportunities
>
> Hi,
>
>
> Attached is the suggested patch.

LGTM.

 -Hal

>
>
> Thanks,
> Olivier
>
>
>
> -----Owen Anderson <resistor at mac.com> wrote: -----
>
> To: Hal Finkel <hfinkel at anl.gov>
> From: Owen Anderson <resistor at mac.com>
> Date: 01/11/2015 10:50PM
> Cc: Olivier H Sallenave/Watson/IBM at IBMUS, llvm-commits at cs.uiuc.edu
> Subject: Re: [PATCH] [LLVMdev] More FMA folding opportunities
>
>
> > On Jan 9, 2015, at 11:19 PM, Hal Finkel <hfinkel at anl.gov> wrote:
> >
> > ----- Original Message -----
> >> From: "Olivier H Sallenave" <ohsallen at us.ibm.com>
> >> To: "Hal Finkel" <hfinkel at anl.gov>
> >> Cc: llvm-commits at cs.uiuc.edu
> >> Sent: Friday, January 9, 2015 11:59:07 AM
> >> Subject: Re: [PATCH] [LLVMdev] More FMA folding opportunities
> >>
> >> Hi Hal,
> >>
> >> I am wondering if we should move the FP_EXTEND cases to the
> >> PPC-specific combiner:
> >>
> >> (fadd (fpext (fmul x, y)), z) -> (fma (fpext x), (fpext y), z)
> >>
> >> We know that for PPC the FPEXT nodes will be removed, but it'll
> >> likely not be the case for other architectures. For those, you end
> >> up with one FMADD rather than one FMUL and one FADD, but also have
> >> two FPEXT nodes rather than one. I would not expect this to take
> >> more cycles to run, but there's no way to systematically check
> >> that
> >> since the cost models are not necessarily accurate.
> >>
> >> In the end, the "aggressive" flag only ensures that you can
> >> combine
> >> one FMUL node with many FADD nodes.
> >>
> >> What do you think?
> >
> > I think we already have too much code in the PPCISelLowering that
> > could be in the target-independent combiner, appropriately
> > guarded. We already have TLI hooks for isTruncateFree, isZExtFree,
> > isFNegFree, isFAbsFree, and we could certainly add an isFPExtFree
> > hook at well.
>
> That would make a lot of sense to me.
>
> —Owen
>
> > -Hal
> >
> >>
> >> Olivier
> >>
> >> Inactive hide details for Hal Finkel ---01/08/2015 08:36:56
> >> PM-------- Original Message ----- > From: "Hal Finkel"
> >> <hfinkel at anlHal Finkel ---01/08/2015 08:36:56 PM-------- Original
> >> Message ----- > From: "Hal Finkel" <hfinkel at anl.gov>
> >>
> >> From: Hal Finkel <hfinkel at anl.gov>
> >> To: Owen Anderson <resistor at mac.com>
> >> Cc: Olivier H Sallenave/Watson/IBM at IBMUS,
> >> <llvm-commits at cs.uiuc.edu>
> >> Date: 01/08/2015 08:36 PM
> >> Subject: Re: [PATCH] [LLVMdev] More FMA folding opportunities
> >>
> >>
> >>
> >>
> >> ----- Original Message -----
> >>> From: "Hal Finkel" <hfinkel at anl.gov>
> >>> To: "Owen Anderson" <resistor at mac.com>
> >>> Cc: "Olivier H Sallenave" <ohsallen at us.ibm.com>,
> >>> llvm-commits at cs.uiuc.edu
> >>> Sent: Thursday, January 8, 2015 6:48:34 PM
> >>> Subject: Re: [PATCH] [LLVMdev] More FMA folding opportunities
> >>>
> >>> ----- Original Message -----
> >>>> From: "Hal Finkel" <hfinkel at anl.gov>
> >>>> To: "Owen Anderson" <resistor at mac.com>
> >>>> Cc: "Olivier H Sallenave" <ohsallen at us.ibm.com>,
> >>>> llvm-commits at cs.uiuc.edu
> >>>> Sent: Thursday, January 8, 2015 6:19:14 PM
> >>>> Subject: Re: [PATCH] [LLVMdev] More FMA folding opportunities
> >>>>
> >>>> ----- Original Message -----
> >>>>> From: "Owen Anderson" <resistor at mac.com>
> >>>>> To: "Hal Finkel" <hfinkel at anl.gov>
> >>>>> Cc: "Olivier H Sallenave" <ohsallen at us.ibm.com>,
> >>>>> llvm-commits at cs.uiuc.edu
> >>>>> Sent: Thursday, January 8, 2015 6:16:57 PM
> >>>>> Subject: Re: [PATCH] [LLVMdev] More FMA folding opportunities
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>> On Jan 8, 2015, at 6:06 PM, Hal Finkel < hfinkel at anl.gov >
> >>>>> wrote:
> >>>>>
> >>>>> Olivier, Aditya is right. You need to add the FP_EXTEND to the
> >>>>> operands of the resulting FMA as appropriate. Can you please
> >>>>> fix
> >>>>> that? We can also move those under the "aggressive" flag for
> >>>>> now.
> >>>>>
> >>>>>
> >>>>> Can you fix or revert this ASAP, please? The missing extends
> >>>>> are
> >>>>> breaking our branches pretty badly.
> >>>>
> >>>> Yep, will do in a few minutes.
> >>>
> >>> I moved the transformations behind the aggressive flag in r225485
> >>> --
> >>> that should unbreak your builds while I fix the extends.
> >>
> >> FP_EXTEND nodes added as of r225492. Thanks for pointing this out!
> >>
> >> -Hal
> >>
> >>>
> >>> -Hal
> >>>
> >>>>
> >>>> -Hal
> >>>>
> >>>>>
> >>>>>
> >>>>> —Owen
> >>>>
> >>>> --
> >>>> Hal Finkel
> >>>> Assistant Computational Scientist
> >>>> Leadership Computing Facility
> >>>> Argonne National Laboratory
> >>>>
> >>>> _______________________________________________
> >>>> llvm-commits mailing list
> >>>> llvm-commits at cs.uiuc.edu
> >>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
> >>>>
> >>>
> >>> --
> >>> Hal Finkel
> >>> Assistant Computational Scientist
> >>> Leadership Computing Facility
> >>> Argonne National Laboratory
> >>>
> >>> _______________________________________________
> >>> llvm-commits mailing list
> >>> llvm-commits at cs.uiuc.edu
> >>> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
> >>>
> >>
> >> --
> >> Hal Finkel
> >> Assistant Computational Scientist
> >> Leadership Computing Facility
> >> Argonne National Laboratory
> >>
> >>
> >>
> >
> > --
> > Hal Finkel
> > Assistant Computational Scientist
> > Leadership Computing Facility
> > Argonne National Laboratory
> >
> > _______________________________________________
> > llvm-commits mailing list
> > llvm-commits at cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>
>

--
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory

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