[Mesa-dev] [PATCH v3 17/43] i965/fs: Enable rounding mode on f2f16 ops

[Chema Casanova]

On 30/10/17 23:40, Jason Ekstrand wrote:
> On Thu, Oct 12, 2017 at 11:38 AM, Jose Maria Casanova Crespo
> <jmcasanova at igalia.com <mailto:jmcasanova at igalia.com>> wrote:
> 
>     From: Alejandro Piñeiro <apinheiro at igalia.com
>     <mailto:apinheiro at igalia.com>>
> 
>     By default we don't set the rounding mode. We only set
>     round-to-near-even or round-to-zero mode if explicitly set from nir.
> 
>     v2: Use a single SHADER_OPCODE_RND_MODE opcode taking an immediate
>         with the rounding mode (Curro)
> 
>     Signed-off-by: Jose Maria Casanova Crespo <jmcasanova at igalia.com
>     <mailto:jmcasanova at igalia.com>>
>     Signed-off-by: Alejandro Piñeiro <apinheiro at igalia.com
>     <mailto:apinheiro at igalia.com>>
>     ---
>      src/intel/compiler/brw_fs_nir.cpp | 8 ++++++++
>      1 file changed, 8 insertions(+)
> 
>     diff --git a/src/intel/compiler/brw_fs_nir.cpp
>     b/src/intel/compiler/brw_fs_nir.cpp
>     index 6908c7ea02..b356836e80 100644
>     --- a/src/intel/compiler/brw_fs_nir.cpp
>     +++ b/src/intel/compiler/brw_fs_nir.cpp
>     @@ -693,6 +693,14 @@ fs_visitor::nir_emit_alu(const fs_builder &bld,
>     nir_alu_instr *instr)
>            inst->saturate = instr->dest.saturate;
>            break;
> 
>     +   case nir_op_f2f16_rtne:
>     +   case nir_op_f2f16_rtz:
>     +      if (instr->op == nir_op_f2f16_rtz)
>     +         bld.emit(SHADER_OPCODE_RND_MODE, bld.null_reg_ud(),
>     brw_imm_d(BRW_RND_MODE_RTZ));
>     +      else if (instr->op == nir_op_f2f16_rtne)
>     +         bld.emit(SHADER_OPCODE_RND_MODE, bld.null_reg_ud(),
>     brw_imm_d(BRW_RND_MODE_RTNE));
>     +      /* fallthrough */
> 
> 
> It might look a little nicer (though it's more lines of code) to have a
> little brw_from_nir_rounding_mode helper and then we could have just the
> one emit call.  I don't care too much though.


What about this helper?

static brw_rnd_mode
brw_rnd_mode_from_nir_op (const nir_op op) {
   switch (op) {
   case nir_op_f2f16_rtz:
      return BRW_RND_MODE_RTZ;
   case nir_op_f2f16_rtne:
      return BRW_RND_MODE_RTNE;
   default:
      unreachable("Operation doesn't support rounding mode");
   }
}

And ...

   case nir_op_f2f16_rtne:
   case nir_op_f2f16_rtz:
      bld.emit(SHADER_OPCODE_RND_MODE, bld.null_reg_ud(),
               brw_imm_d(brw_rnd_mode_from_nir_op(instr->op)));


> 
>     +
>            /* In theory, it would be better to use BRW_OPCODE_F32TO16.
>     Depending
>             * on the HW gen, it is a special hw opcode or just a MOV, and
>             * brw_F32TO16 (at brw_eu_emit) would do the work to chose.
>     --
>     2.13.6
> 
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> 
> 
> 
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