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

[Jason Ekstrand]

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.
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