[Mesa-dev] [PATCH 2/2] R600: Add a pattern for fma (fused multiply add)

[Tom Stellard]

On Fri, Feb 08, 2013 at 12:12:26PM +0100, Michel Dänzer wrote:
> On Don, 2013-02-07 at 17:23 -0500, Tom Stellard wrote: 
> > From: Tom Stellard <thomas.stellard at amd.com>
> > 
> > NOTE: This is a candidate for the Mesa stable branches
> > ---
> >  lib/Target/R600/R600Instructions.td |    7 +++++++
> >  1 files changed, 7 insertions(+), 0 deletions(-)
> > 
> > diff --git a/lib/Target/R600/R600Instructions.td b/lib/Target/R600/R600Instructions.td
> > index d307ed2..07ee6f0 100644
> > --- a/lib/Target/R600/R600Instructions.td
> > +++ b/lib/Target/R600/R600Instructions.td
> > @@ -1109,6 +1109,11 @@ class TGSI_LIT_Z_Common <InstR600 mul_lit, InstR600 log_clamped, InstR600 exp_ie
> >    (exp_ieee (mul_lit (log_clamped (MAX R600_Reg32:$src_y, (f32 ZERO))), R600_Reg32:$src_w, R600_Reg32:$src_x))
> >  >;
> >  
> > +class FMAPat <InstR600 muladd> : Pat<
> > +  (fma R600_Reg32:$src0, R600_Reg32:$src1, R600_Reg32:$src2),
> > +  (muladd R600_Reg32:$src0, R600_Reg32:$src1, R600_Reg32:$src2)
> > +>;
> > +
> >  //===----------------------------------------------------------------------===//
> >  // R600 / R700 Instructions
> >  //===----------------------------------------------------------------------===//
> > @@ -1167,6 +1172,7 @@ let Predicates = [isR600] in {
> >      let Word1{31} = 1; // BARRIER
> >    }
> >    defm : SteamOutputExportPattern<R600_ExportBuf, 0x20, 0x21, 0x22, 0x23>;
> > +  def : FMAPat <MULADD_r600>;
> >  }
> >  
> >  // Helper pattern for normalizing inputs to triginomic instructions for R700+
> > @@ -1320,6 +1326,7 @@ let hasSideEffects = 1 in {
> >      let Word1{31} = 1; // BARRIER
> >    }
> >    defm : SteamOutputExportPattern<EG_ExportBuf, 0x40, 0x41, 0x42, 0x43>;
> > +  def : FMAPat <MULADD_eg>;
> >  
> >  //===----------------------------------------------------------------------===//
> >  // Memory read/write instructions
> 
> Do the MULADD instructions match the FMA semantics, i.e. they don't
> round/truncate the intermediate product but only the final sum?
> 

They are different and actually the hardware has an FMA instruction,
which I didn't notice before, so I'll use that instead.

-Tom

> 
> Patch 1 looks nice and is
> 
> Reviewed-by: Michel Dänzer <michel.daenzer at amd.com>
> 
> 
> -- 
> Earthling Michel Dänzer           |                   http://www.amd.com
> Libre software enthusiast         |          Debian, X and DRI developer