[Mesa-dev] [PATCH 01/11] glsl: Allow dynamically uniform sampler array indexing with 4.0/gs5

[Matt Turner]

On Sat, Aug 9, 2014 at 7:14 PM, Chris Forbes <chrisf at ijw.co.nz> wrote:
> Signed-off-by: Chris Forbes <chrisf at ijw.co.nz>
> ---
>  src/glsl/ast_array_index.cpp | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/src/glsl/ast_array_index.cpp b/src/glsl/ast_array_index.cpp
> index 50f9987..f8dca80 100644
> --- a/src/glsl/ast_array_index.cpp
> +++ b/src/glsl/ast_array_index.cpp
> @@ -213,6 +213,9 @@ _mesa_ast_array_index_to_hir(void *mem_ctx,
>         * as using a loop counter as the index to an array of samplers.  If the
>         * loop in unrolled, the code should compile correctly.  Instead, emit a
>         * warning.
> +       *
> +       * In GLSL 4.00 / ARB_gpu_shader5, this requirement is relaxed again to allow
> +       * indexing with dynamically uniform expressions.
>         */
>        if (array->type->element_type()->is_sampler()) {
>          if (!state->is_version(130, 100)) {
> @@ -227,7 +230,7 @@ _mesa_ast_array_index_to_hir(void *mem_ctx,
>                                   "expressions will be forbidden in GLSL 1.30 "
>                                   "and later");
>             }
> -        } else {
> +        } else if (!state->is_version(400, 0) && !state->ARB_gpu_shader5_enable) {
>             _mesa_glsl_error(&loc, state,
>                              "sampler arrays indexed with non-constant "
>                              "expressions is forbidden in GLSL 1.30 and "
> --

I was initially confused, expecting a check that the index is a
uniform. But all that's required is that it's a uniform *expression*,
which is much more difficult to determine. And the spec says that
non-uniform expressions just yield undefined results. Maybe extend the
comment to note that, but maybe don't worry about it.