[Mesa-dev] [PATCH v3 14/43] i965/fs: Handle 32-bit to 16-bit conversions

[Pohjolainen, Topi]

On Thu, Oct 12, 2017 at 08:38:03PM +0200, Jose Maria Casanova Crespo wrote:
> From: Alejandro Piñeiro <apinheiro at igalia.com>
> 
> Conversions to 16-bit need having aligment between the 16-bit
> and 32-bit types. So the conversion operations unpack 16-bit types
> to with an stride=2 and then applies a MOV with the conversion.
> 
> v2 (Jason Ekstrand):
>   - Avoid the general use of stride=2 for 16-bit register types.
> 
> Signed-off-by: Eduardo Lima <elima at igalia.com>
> Signed-off-by: Alejandro Piñeiro <apinheiro at igalia.com>
> Signed-off-by: Jose Maria Casanova Crespo <jmcasanova at igalia.com>
> ---
>  src/intel/compiler/brw_fs_nir.cpp | 25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
> 
> diff --git a/src/intel/compiler/brw_fs_nir.cpp b/src/intel/compiler/brw_fs_nir.cpp
> index affe65d5e9..6908c7ea02 100644
> --- a/src/intel/compiler/brw_fs_nir.cpp
> +++ b/src/intel/compiler/brw_fs_nir.cpp
> @@ -693,6 +693,31 @@ fs_visitor::nir_emit_alu(const fs_builder &bld, nir_alu_instr *instr)
>        inst->saturate = instr->dest.saturate;
>        break;
>  
> +      /* 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.
> +       *
> +       * But if we want to use that opcode, we need to provide support on
> +       * different optimizations and lowerings. As right now HF support is
> +       * only for gen8+, it will be better to use directly the MOV, and use
> +       * BRW_OPCODE_F32TO16 when/if we work for HF support on gen7.
> +       */
> +
> +   case nir_op_f2f16:
> +   case nir_op_i2i16:
> +   case nir_op_u2u16: {
> +      /* TODO: Fixing aligment rules for conversions from 32-bits to
> +       * 16-bit types should be moved to lower_conversions
> +       */
> +      fs_reg tmp = bld.vgrf(op[0].type, 1);
> +      tmp = subscript(tmp, result.type, 0);
> +      inst = bld.MOV(tmp, op[0]);
> +      inst->saturate = instr->dest.saturate;
> +      inst = bld.MOV(result ,tmp);

Move space after ','

> +      inst->saturate = instr->dest.saturate;
> +      break;
> +   }
> +
>     case nir_op_f2f64:
>     case nir_op_i2f64:
>     case nir_op_u2f64:
> -- 
> 2.13.6
> 
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