[PATCH] Fw: [LLVMdev] More FMA folding opportunities

[Hal Finkel]

----- 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: Tuesday, January 6, 2015 8:03:51 PM
> Subject: Re: [PATCH] Fw: [LLVMdev] More FMA folding opportunities
> 
> 
> 
> Hal,
> 
> You're right, I moved those heuristics in the target-independent
> combiner.

LGTM. Do you have commit access?

 -Hal

> 
> Thanks,
> Olivier
> 
> (See attached file: patch-v3.diff)
> 
> Inactive hide details for Hal Finkel ---01/06/2015 06:52:06
> PM-------- Original Message ----- > From: "Olivier H Sallenave"
> <ohHal Finkel ---01/06/2015 06:52:06 PM-------- Original Message
> ----- > From: "Olivier H Sallenave" <ohsallen at us.ibm.com>
> 
> From: Hal Finkel <hfinkel at anl.gov>
> To: Olivier H Sallenave/Watson/IBM at IBMUS
> Cc: <llvm-commits at cs.uiuc.edu>
> Date: 01/06/2015 06:52 PM
> Subject: Re: [PATCH] Fw: [LLVMdev] More FMA folding opportunities
> 
> 
> 
> 
> ----- Original Message -----
> > From: "Olivier H Sallenave" <ohsallen at us.ibm.com>
> > To: llvm-commits at cs.uiuc.edu
> > Cc: "Hal Finkel" <hfinkel at anl.gov>
> > Sent: Monday, January 5, 2015 9:51:22 AM
> > Subject: Fw: [PATCH] Fw: [LLVMdev] More FMA folding opportunities
> > 
> > 
> > 
> > Hi,
> > 
> > Here's a more comprehensive patch also handling the fact that
> > FP_EXTEND will later be removed for PPC. Accordingly, new patterns
> > are implemented in the PPC-specific combiner:
> 
> Given that these are predicated on (TM.Options.UnsafeFPMath ||
> TM.Options.AllowFPOpFusion == FPOpFusion::Fast), what makes them PPC
> specific? Either of those two options allow us to compute the
> relevant operations with extra precision, right?
> 
> -Hal
> 
> > 
> > > Finally, specifically for the PPC target, we could ignore
> > > FP_EXTEND
> > > in the patterns above as it will be removed by the Machine Common
> > > Subexpression Elimination pass. For instance:
> > > 
> > > fold (fadd (fpext (fmul x, y)), z) -> (fma x, y, z)
> > > fold (fadd (fpext (fma x, y, (fmul u, v))), z) -> (fma x, y (fma
> > > u,
> > > v, z))
> > 
> > I also moved the tests in new files (fma-ext.ll, fma-assoc.ll) for
> > more clarity.
> > 
> > Thanks,
> > Olivier
> > 
> > (See attached file: patch-v2.diff)
> > 
> > 
> > 
> > ----- Forwarded by Olivier H Sallenave/Watson/IBM on 01/05/2015
> > 10:44
> > AM -----
> > 
> > From: Olivier H Sallenave/Watson/IBM
> > To: llvm-commits at cs.uiuc.edu
> > Cc: "Hal Finkel" <hfinkel at anl.gov>
> > Date: 12/29/2014 05:09 PM
> > Subject: [PATCH] Fw: [LLVMdev] More FMA folding opportunities
> > 
> > 
> > 
> > Hi,
> > 
> > Attached is a patch to support more FMA folding opportunities
> > (especially for PPC) as discussed below.
> > 
> > Thanks,
> > Olivier
> > 
> > (See attached file: patch.diff)
> > 
> > 
> > 
> > ----- Forwarded by Olivier H Sallenave/Watson/IBM on 12/29/2014
> > 04:56
> > PM -----
> > 
> > From: Hal Finkel <hfinkel at anl.gov>
> > To: Olivier H Sallenave/Watson/IBM at IBMUS
> > Cc: <llvmdev at cs.uiuc.edu>
> > Date: 09/30/2014 08:08 PM
> > Subject: Re: [LLVMdev] More FMA folding opportunities
> > 
> > 
> > 
> > 
> > ----- Original Message -----
> > > From: "Olivier H Sallenave" <ohsallen at us.ibm.com>
> > > To: llvmdev at cs.uiuc.edu
> > > Sent: Monday, September 29, 2014 3:34:51 PM
> > > Subject: [LLVMdev] More FMA folding opportunities
> > > 
> > > Hi,
> > > 
> > > I think more opportunities might be added for FMA in the DAG
> > > combiner, please tell me what you think. Right now, those cases
> > > are
> > > implemented:
> > > 
> > > fold (fadd (fmul x, y), z) -> (fma x, y, z)
> > > fold (fadd x, (fmul y, z)) -> (fma y, z, x)
> > > 
> > > When the TLI callback "enableAggressiveFMAFusion" returns true,
> > > we
> > > might also support:
> > > 
> > > fold (fadd (fma x, y, (fmul u, v)), z) -> (fma x, y (fma u, v,
> > > z))
> > > fold (fadd x, (fma y, z, (fmul u, v)) -> (fma y, z (fma u, v, x))
> > > 
> > > This kind of reassociation generates two FMA for (x^2 + y^2 + z).
> > 
> > Yes, this all sounds reasonable.
> > 
> > Thanks again,
> > Hal
> 
> --
> Hal Finkel
> Assistant Computational Scientist
> Leadership Computing Facility
> Argonne National Laboratory
> 
> 

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