[Mesa-dev] [RFC PATCH] glsl: keep track of ssbo variable being accessed, add access params

[Ilia Mirkin]

On Tue, Dec 29, 2015 at 4:52 PM, Jason Ekstrand <jason at jlekstrand.net> wrote:
>
>
> On Tue, Dec 29, 2015 at 1:50 PM, Ilia Mirkin <imirkin at alum.mit.edu> wrote:
>>
>> On Tue, Dec 29, 2015 at 4:45 PM, Jason Ekstrand <jason at jlekstrand.net>
>> wrote:
>> >
>> >
>> > On Mon, Dec 28, 2015 at 11:06 AM, Ilia Mirkin <imirkin at alum.mit.edu>
>> > wrote:
>> >>
>> >> Currently any access params (coherent/volatile/restrict) are being lost
>> >> when lowering to the ssbo load/store intrinsics. Keep track of the
>> >> variable being used, and bake its access params in as the last arg of
>> >> the load/store intrinsics.
>> >>
>> >> Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
>> >> ---
>> >>
>> >> This is RFC because there are still no users, but I'm working on that.
>> >> Don't
>> >> want to be going in the completely wrong direction though...
>> >>
>> >>  src/glsl/lower_ubo_reference.cpp | 22 ++++++++++++++++++++++
>> >>  1 file changed, 22 insertions(+)
>> >>
>> >> diff --git a/src/glsl/lower_ubo_reference.cpp
>> >> b/src/glsl/lower_ubo_reference.cpp
>> >> index a172054..5b3f523 100644
>> >> --- a/src/glsl/lower_ubo_reference.cpp
>> >> +++ b/src/glsl/lower_ubo_reference.cpp
>> >> @@ -104,6 +104,7 @@ public:
>> >>
>> >>     struct gl_shader *shader;
>> >>     struct gl_uniform_buffer_variable *ubo_var;
>> >> +   ir_variable *variable;
>> >>     ir_rvalue *uniform_block;
>> >>     bool progress;
>> >>  };
>> >> @@ -317,6 +318,7 @@
>> >> lower_ubo_reference_visitor::handle_rvalue(ir_rvalue
>> >> **rvalue)
>> >>     this->buffer_access_type =
>> >>        var->is_in_shader_storage_block() ?
>> >>        ssbo_load_access : ubo_load_access;
>> >> +   this->variable = var;
>> >>
>> >>     /* Compute the offset to the start if the dereference as well as
>> >> other
>> >>      * information we need to configure the write
>> >> @@ -370,6 +372,13 @@ shader_storage_buffer_object(const
>> >> _mesa_glsl_parse_state *state)
>> >>     return state->ARB_shader_storage_buffer_object_enable;
>> >>  }
>> >>
>> >> +static uint32_t ssbo_access_params(const ir_variable *var)
>> >> +{
>> >> +   return (var->data.image_coherent << 0) |
>> >> +          (var->data.image_volatile << 1) |
>> >> +          (var->data.image_restrict << 2);
>> >
>> >
>> > Do 0, 1, and 2 have some special meaning I should know about?  I suggest
>> > we
>> > add an enum to shader_enums.h.
>>
>> Do you mean a struct with a bitfield? That'd work for me.
>
> Well, if you want to pack it into a function argument you intend to bake
> into the shader source, that won't work so well.  It needs to be an integer
> in the end.  If you want to do a union and a bitfield, that's fine, but I
> think an enum is more customary.

Er right... I want an integer in the end. But I want all 3 values to
be packed into it... I could add defines for 1, 2, and 4, like
SSBO_COHERENT, SSBO_VOLATILE, SSBO_RESTRICT. An enum seems wrong since
it's a bitfield with multiple possible bits set, not an enumeration.

  -ilia