[Mesa-dev] [PATCH v4 2/3] i965/fs: Use NIR's scalarizing abilities and stop handling vectors

[Matt Turner]

On Tue, Jan 27, 2015 at 5:31 PM, Jason Ekstrand <jason at jlekstrand.net> wrote:
> diff --git a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
> index de0d780..217fe09 100644
> @@ -689,9 +689,9 @@ fs_visitor::nir_emit_alu(nir_alu_instr *instr)
>
>        struct brw_reg acc = retype(brw_acc_reg(dispatch_width), result.type);
>
> -      emit_percomp(MUL(acc, op[0], op[1]), instr->dest.write_mask);
> -      emit_percomp(MACH(reg_null_d, op[0], op[1]), instr->dest.write_mask);
> -      emit_percomp(MOV(result, fs_reg(acc)), instr->dest.write_mask);

Bah. How the hell did the old code pass piglit?

> +      emit(MUL(acc, op[0], op[1]));
> +      emit(MACH(reg_null_d, op[0], op[1]));
> +      emit(MOV(result, fs_reg(acc)));
>        break;
>     }
>
> @@ -773,72 +767,38 @@ fs_visitor::nir_emit_alu(nir_alu_instr *instr)
>     case nir_op_ball_fequal3:
>     case nir_op_ball_iequal3:
>     case nir_op_ball_fequal4:
> -   case nir_op_ball_iequal4: {
> -      unsigned num_components = nir_op_infos[instr->op].input_sizes[0];
> -      fs_reg temp = vgrf(num_components);
> -      emit_percomp(CMP(temp, op[0], op[1], BRW_CONDITIONAL_Z),
> -                   (1 << num_components) - 1);
> -      emit_reduction(BRW_OPCODE_AND, result, temp, num_components);
> -      break;
> -   }
> -
> +   case nir_op_ball_iequal4:

We can save it for later, but it might be interesting to let the fs
backend get the vector comparisons directly, if that's possible.

See https://bugs.freedesktop.org/show_bug.cgi?id=77456

> @@ -867,83 +827,67 @@ fs_visitor::nir_emit_alu(nir_alu_instr *instr)
>        unreachable("not reached: should be handled by ldexp_to_arith()");
>
>     case nir_op_fsqrt:
> -      emit_math_percomp(SHADER_OPCODE_SQRT, result, op[0],
> -                        instr->dest.write_mask, instr->dest.saturate);
> +      emit_math(SHADER_OPCODE_SQRT, result, op[0])
> +               ->saturate = instr->dest.saturate;

I don't really like the ->saturate = ... as a single statement. I know
I'm guilty of using it in a unit test recently.

I guess if we remove saturate as a destination modifier from NIR we'll
get rid of most instances of this pattern, leaving just ->predicate.
Are we planning to remove src/dst modifiers from NIR?