[Mesa-dev] [PATCH 28/59] intel/compiler: set correct precision fields for 3-source float instructions

[Iago Toral]

On Wed, 2018-12-05 at 14:58 +0200, Pohjolainen, Topi wrote:
> On Tue, Dec 04, 2018 at 08:16:52AM +0100, Iago Toral Quiroga wrote:
> > Source0 and Destination extract the floating-point precision
> > automatically
> > from the SrcType and DstType instruction fields respectively when
> > they are
> > set to types :F or :HF. For Source1 and Source2 operands, we use
> > the new
> > 1-bit fields Src1Type and Src2Type, where 0 means normal precision
> > and 1
> > means half-precision. Since we always use the type of the
> > destination for
> > all operands when we emit 3-source instructions, we only need set
> > Src1Type
> > and Src2Type to 1 when we are emitting a half-precision
> > instruction.
> > ---
> >  src/intel/compiler/brw_eu_emit.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> > 
> > diff --git a/src/intel/compiler/brw_eu_emit.c
> > b/src/intel/compiler/brw_eu_emit.c
> > index 2c9fc9a5c7c..66edfb43baf 100644
> > --- a/src/intel/compiler/brw_eu_emit.c
> > +++ b/src/intel/compiler/brw_eu_emit.c
> > @@ -801,6 +801,11 @@ brw_alu3(struct brw_codegen *p, unsigned
> > opcode, struct brw_reg dest,
> >            */
> >           brw_inst_set_3src_a16_src_type(devinfo, inst, dest.type);
> >           brw_inst_set_3src_a16_dst_type(devinfo, inst, dest.type);
> > +
> > +         if (devinfo->gen >= 8 && dest.type ==
> > BRW_REGISTER_TYPE_HF) {
> > +            brw_inst_set_3src_a16_src1_type(devinfo, inst, 1);
> > +            brw_inst_set_3src_a16_src2_type(devinfo, inst, 1);
> > +         }
> 
> I had similar patch which prepares for mixed mode (useful for linterp
> with
> 32-bit input varyings):
> 
>          /* From the Bspec: Instruction types
>           *
>           * Three source instructions can use operands with mixed-
> mode
>           * precision. When SrcType field is set to :f or :hf it
> defines
>           * precision for source 0 only, and fields Src1Type and
> Src2Type
>           * define precision for other source operands:
>           *
>           *   0b = :f. Single precision Float (32-bit).
>           *   1b = :hf. Half precision Float (16-bit).
>           */
>          if (src1.type == BRW_REGISTER_TYPE_HF)
>             brw_inst_set_3src_src1_type(devinfo, inst, 1);
> 
>          if (src2.type == BRW_REGISTER_TYPE_HF)
>             brw_inst_set_3src_src2_type(devinfo, inst, 1);
> 
> How would you feel about that? (Direct cut-paste and the helpers have
> different name).

Sure, if we are planning to use mixed mode in the future this makes
more sense. Thanks!

> >        }
> >     }
> >  
> > -- 
> > 2.17.1
> > 
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> 
>