[Mesa-dev] [PATCH] prog_to_nir: Don't allocate nir_variable with type vec4[0] for uniforms.

[Jason Ekstrand]

Reviewed-by: Jason Ekstrand <jason.ekstrand at intel.com>

On Mon, Aug 24, 2015 at 4:39 PM, Kenneth Graunke <kenneth at whitecape.org> wrote:
> If there are no parameters, we don't need to create a nir_variable to
> hold them...and allocating an array of length 0 is pretty bogus.
>
> Should avoid i965 backend assertions in future patches Jason and I are
> working on.
>
> Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
> ---
>  src/mesa/program/prog_to_nir.c | 18 +++++++++++-------
>  1 file changed, 11 insertions(+), 7 deletions(-)
>
> Hey Jason,
>
> It sounds like the right thing to do is make prog_to_nir stop generating
> idiotic shader code.  Here's a patch that does that.
>
> The assert you're removing may still be unnecessary, but it also seems
> like a totally reasonable thing for the backend to enforce...so I'd prefer
> to leave it...
>
> --Ken
>
> diff --git a/src/mesa/program/prog_to_nir.c b/src/mesa/program/prog_to_nir.c
> index e088578..29ff638 100644
> --- a/src/mesa/program/prog_to_nir.c
> +++ b/src/mesa/program/prog_to_nir.c
> @@ -167,6 +167,8 @@ ptn_get_src(struct ptn_compile *c, const struct prog_src_register *prog_src)
>           }
>           /* FALLTHROUGH */
>        case PROGRAM_STATE_VAR: {
> +         assert(c->parameters != NULL);
> +
>           nir_intrinsic_instr *load =
>              nir_intrinsic_instr_create(b->shader, nir_intrinsic_load_var);
>           nir_ssa_dest_init(&load->instr, &load->dest, 4, NULL);
> @@ -1090,13 +1092,15 @@ prog_to_nir(const struct gl_program *prog,
>        goto fail;
>     c->prog = prog;
>
> -   c->parameters = rzalloc(s, nir_variable);
> -   c->parameters->type = glsl_array_type(glsl_vec4_type(),
> -                                            prog->Parameters->NumParameters);
> -   c->parameters->name = "parameters";
> -   c->parameters->data.read_only = true;
> -   c->parameters->data.mode = nir_var_uniform;
> -   exec_list_push_tail(&s->uniforms, &c->parameters->node);
> +   if (prog->Parameters->NumParameters > 0) {
> +      c->parameters = rzalloc(s, nir_variable);
> +      c->parameters->type =
> +         glsl_array_type(glsl_vec4_type(), prog->Parameters->NumParameters);
> +      c->parameters->name = "parameters";
> +      c->parameters->data.read_only = true;
> +      c->parameters->data.mode = nir_var_uniform;
> +      exec_list_push_tail(&s->uniforms, &c->parameters->node);
> +   }
>
>     nir_function *func = nir_function_create(s, "main");
>     nir_function_overload *overload = nir_function_overload_create(func);
> --
> 2.5.0
>
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