[Mesa-dev] [PATCH] i965: Emit better code for ir_unop_sign.

[Kenneth Graunke]

On 12/02/2013 01:46 PM, Matt Turner wrote:
> total instructions in shared programs: 1519751 -> 1519442 (-0.02%)
> instructions in affected programs:     10154 -> 9845 (-3.04%)
> ---
>  src/mesa/drivers/dri/i965/brw_fs_visitor.cpp   | 23 +++++++++++++++--------
>  src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp | 23 ++++++++++++++++-------
>  2 files changed, 31 insertions(+), 15 deletions(-)
> 
> diff --git a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
> index 9eb9a9d..a0e803b 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
> @@ -382,18 +382,25 @@ fs_visitor::visit(ir_expression *ir)
>        emit(MOV(this->result, op[0]));
>        break;
>     case ir_unop_sign:
> -      temp = fs_reg(this, ir->type);
> +      if (ir->type->is_float()) {
> +         emit(CMP(reg_null_f, op[0], fs_reg(0.0f), BRW_CONDITIONAL_NZ));
>  
> -      emit(MOV(this->result, fs_reg(0.0f)));
> +         op[0].type = BRW_REGISTER_TYPE_UD;
> +         this->result.type = BRW_REGISTER_TYPE_UD;
> +         emit(AND(this->result, op[0], fs_reg(0x80000000u)));
>  
> -      emit(CMP(reg_null_f, op[0], fs_reg(0.0f), BRW_CONDITIONAL_G));
> -      inst = emit(MOV(this->result, fs_reg(1.0f)));
> -      inst->predicate = BRW_PREDICATE_NORMAL;
> +         inst = emit(OR(this->result, this->result, fs_reg(0x3f800000u)));
> +         inst->predicate = BRW_PREDICATE_NORMAL;
>  
> -      emit(CMP(reg_null_f, op[0], fs_reg(0.0f), BRW_CONDITIONAL_L));
> -      inst = emit(MOV(this->result, fs_reg(-1.0f)));
> -      inst->predicate = BRW_PREDICATE_NORMAL;
> +         this->result.type = BRW_REGISTER_TYPE_F;
> +      } else {
> +         emit(CMP(reg_null_d, op[0], fs_reg(0), BRW_CONDITIONAL_G));
>  
> +         emit(ASR(this->result, op[0], fs_reg(31)));
> +
> +         inst = emit(OR(this->result, this->result, fs_reg(1)));
> +         inst->predicate = BRW_PREDICATE_NORMAL;
> +      }
>        break;
>     case ir_unop_rcp:
>        emit_math(SHADER_OPCODE_RCP, this->result, op[0]);
> diff --git a/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp b/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
> index a13eafb..986663b 100644
> --- a/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
> @@ -1259,16 +1259,25 @@ vec4_visitor::visit(ir_expression *ir)
>        break;
>  
>     case ir_unop_sign:
> -      emit(MOV(result_dst, src_reg(0.0f)));
> +      if (ir->type->is_float()) {
> +         emit(CMP(dst_null_f(), op[0], src_reg(0.0f), BRW_CONDITIONAL_NZ));
>  
> -      emit(CMP(dst_null_d(), op[0], src_reg(0.0f), BRW_CONDITIONAL_G));
> -      inst = emit(MOV(result_dst, src_reg(1.0f)));
> -      inst->predicate = BRW_PREDICATE_NORMAL;
> +         op[0].type = BRW_REGISTER_TYPE_UD;
> +         result_dst.type = BRW_REGISTER_TYPE_UD;
> +         emit(AND(result_dst, op[0], src_reg(0x80000000u)));
>  
> -      emit(CMP(dst_null_d(), op[0], src_reg(0.0f), BRW_CONDITIONAL_L));
> -      inst = emit(MOV(result_dst, src_reg(-1.0f)));
> -      inst->predicate = BRW_PREDICATE_NORMAL;
> +         inst = emit(OR(result_dst, src_reg(result_dst), src_reg(0x3f800000u)));
> +         inst->predicate = BRW_PREDICATE_NORMAL;
> +
> +         this->result.type = BRW_REGISTER_TYPE_F;
> +      } else {
> +         emit(CMP(dst_null_d(), op[0], src_reg(0), BRW_CONDITIONAL_G));
> +
> +         emit(ASR(result_dst, op[0], src_reg(31)));
>  
> +         inst = emit(OR(result_dst, src_reg(result_dst), src_reg(1)));
> +         inst->predicate = BRW_PREDICATE_NORMAL;
> +      }
>        break;
>  
>     case ir_unop_rcp:

Some comments in both cases would be great.  But this looks correct, and
definitely more efficient.

Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>