[Mesa-dev] [PATCH 2/2] i965/fs: Emit MADs from (x + abs(y * z)).

[Kristian Høgsberg]

On Tue, Jan 13, 2015 at 3:00 PM, Matt Turner <mattst88 at gmail.com> wrote:
> Just use the abs source modifier on both of the multiplicand
> arguments.
>
> instructions in affected programs:     300 -> 296 (-1.33%)

Reviewed-by: Kristian Høgsberg <krh at bitplanet.net>

> ---
>  src/mesa/drivers/dri/i965/brw_fs_visitor.cpp | 18 +++++++++++++++---
>  1 file changed, 15 insertions(+), 3 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
> index dd4beff..9c4f5e8 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
> @@ -426,8 +426,11 @@ fs_visitor::try_emit_mad(ir_expression *ir)
>     ir_rvalue *nonmul = ir->operands[1];
>     ir_expression *mul = ir->operands[0]->as_expression();
>
> -   bool mul_negate = false;
> -   if (mul && mul->operation == ir_unop_neg) {
> +   bool mul_negate = false, mul_abs = false;
> +   if (mul && mul->operation == ir_unop_abs) {
> +      mul = mul->operands[0]->as_expression();
> +      mul_abs = true;
> +   } else if (mul && mul->operation == ir_unop_neg) {
>        mul = mul->operands[0]->as_expression();
>        mul_negate = true;
>     }
> @@ -436,7 +439,10 @@ fs_visitor::try_emit_mad(ir_expression *ir)
>        nonmul = ir->operands[0];
>        mul = ir->operands[1]->as_expression();
>
> -      if (mul && mul->operation == ir_unop_neg) {
> +      if (mul && mul->operation == ir_unop_abs) {
> +         mul = mul->operands[0]->as_expression();
> +         mul_abs = true;
> +      } else if (mul && mul->operation == ir_unop_neg) {
>           mul = mul->operands[0]->as_expression();
>           mul_negate = true;
>        }
> @@ -456,9 +462,15 @@ fs_visitor::try_emit_mad(ir_expression *ir)
>     mul->operands[0]->accept(this);
>     fs_reg src1 = this->result;
>     src1.negate ^= mul_negate;
> +   src1.abs = mul_abs;
> +   if (mul_abs)
> +      src1.negate = false;
>
>     mul->operands[1]->accept(this);
>     fs_reg src2 = this->result;
> +   src2.abs = mul_abs;
> +   if (mul_abs)
> +      src2.negate = false;
>
>     this->result = fs_reg(this, ir->type);
>     emit(BRW_OPCODE_MAD, this->result, src0, src1, src2);
> --
> 2.0.4
>
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