[Mesa-dev] [PATCH] st/mesa: fix weird UCMP opcode use for bool ubo load

[Marek Olšák]

Reviewed-by: Marek Olšák <maraeo at gmail.com>

Marek

On Thu, May 9, 2013 at 12:58 AM,  <sroland at vmware.com> wrote:
> From: Roland Scheidegger <sroland at vmware.com>
>
> I don't know what this code was trying to do but whatever it was it couldn't
> have worked since negation of integer boolean inputs while not specified as
> outright illegal (not yet at least) won't do anything since it doesn't affect
> the result of comparison with zero at all. In fact it looks like the whole
> instruction can just be omitted.
> ---
>  src/mesa/state_tracker/st_glsl_to_tgsi.cpp |    6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
> index f2eb3e7..08b2d7a 100644
> --- a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
> +++ b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
> @@ -1945,8 +1945,6 @@ glsl_to_tgsi_visitor::visit(ir_expression *ir)
>
>        if (ir->type->base_type == GLSL_TYPE_BOOL) {
>           emit(ir, TGSI_OPCODE_USNE, result_dst, cbuf, st_src_reg_for_int(0));
> -         result_src.negate = 1;
> -         emit(ir, TGSI_OPCODE_UCMP, result_dst, result_src, st_src_reg_for_int(~0), st_src_reg_for_int(0));
>        } else {
>           emit(ir, TGSI_OPCODE_MOV, result_dst, cbuf);
>        }
> @@ -2388,8 +2386,8 @@ glsl_to_tgsi_visitor::visit(ir_assignment *ir)
>           if (native_integers) {
>              /* This is necessary because TGSI's CMP instruction expects the
>               * condition to be a float, and we store booleans as integers.
> -             * If TGSI had a UCMP instruction or similar, this extra
> -             * instruction would not be necessary.
> +             * TODO: really want to avoid i2f path and use UCMP. Requires
> +             * changes to process_move_condition though too.
>               */
>              condition_temp = get_temp(glsl_type::vec4_type);
>              condition.negate = 0;
> --
> 1.7.9.5
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