On Tue, Jan 13, 2015 at 3:00 PM, Matt Turner <matts...@gmail.com> wrote:
> Just use the negation source modifier on one of the multiplicand
> arguments.
>
> total instructions in shared programs: 5889529 -> 5880016 (-0.16%)
> instructions in affected programs: 600846 -> 591333 (-1.58%)
Reviewed-by: Kristian Høgsberg <k...@bitplanet.net>
> ---
> src/mesa/drivers/dri/i965/brw_fs_visitor.cpp | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
> b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
> index bd9345e..dd4beff 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
> @@ -426,10 +426,21 @@ 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) {
> + mul = mul->operands[0]->as_expression();
> + mul_negate = true;
> + }
> +
> if (!mul || mul->operation != ir_binop_mul) {
> nonmul = ir->operands[0];
> mul = ir->operands[1]->as_expression();
>
> + if (mul && mul->operation == ir_unop_neg) {
> + mul = mul->operands[0]->as_expression();
> + mul_negate = true;
> + }
> +
> if (!mul || mul->operation != ir_binop_mul)
> return false;
> }
> @@ -444,6 +455,7 @@ fs_visitor::try_emit_mad(ir_expression *ir)
>
> mul->operands[0]->accept(this);
> fs_reg src1 = this->result;
> + src1.negate ^= mul_negate;
>
> mul->operands[1]->accept(this);
> fs_reg src2 = this->result;
> --
> 2.0.4
>
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