[Mesa-dev] [PATCH 2/5] glsl: Optionally lower TES gl_PatchVerticesIn to a uniform.

[Kenneth Graunke]

On Wednesday, June 8, 2016 7:45:16 PM PDT Alejandro Piñeiro wrote:
> On 02/06/16 23:09, Kenneth Graunke wrote:
> > i965 has no special hardware for this, so we need to pass this value in
> > as a uniform (unless the TES is linked against a TCS, in which case the
> > linker can just replace this with a constant).
> >
> > Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
> > Cc: mesa-stable at lists.freedesktop.org
> > ---
> >  src/compiler/glsl/linker.cpp      | 20 +++++++++++++++++---
> >  src/mesa/main/mtypes.h            |  1 +
> >  src/mesa/program/prog_statevars.c |  7 +++++++
> >  src/mesa/program/prog_statevars.h |  1 +
> >  4 files changed, 26 insertions(+), 3 deletions(-)
> >
> > diff --git a/src/compiler/glsl/linker.cpp b/src/compiler/glsl/linker.cpp
> > index 9e65590..7c7dbfe 100644
> > --- a/src/compiler/glsl/linker.cpp
> > +++ b/src/compiler/glsl/linker.cpp
> > @@ -72,6 +72,7 @@
> >  #include "ir.h"
> >  #include "program.h"
> >  #include "program/hash_table.h"
> > +#include "program/prog_instruction.h"
> >  #include "linker.h"
> >  #include "link_varyings.h"
> >  #include "ir_optimization.h"
> > @@ -2485,7 +2486,7 @@ resize_tes_inputs(struct gl_context *ctx,
> >        ir->accept(&input_resize_visitor);
> >     }
> >  
> > -   if (tcs) {
> > +   if (tcs || ctx->Const.LowerTESPatchVerticesIn) {
> >        /* Convert the gl_PatchVerticesIn system value into a constant, since
> >         * the value is known at this point.
> 
> Now this comment became obsolete as can be converted to a constant or a
> uniform. Perhaps it would be better to just remove the comment.
> 
> >         */
> > @@ -2494,9 +2495,22 @@ resize_tes_inputs(struct gl_context *ctx,
> >           if (var && var->data.mode == ir_var_system_value &&
> >               var->data.location == SYSTEM_VALUE_VERTICES_IN) {
> >              void *mem_ctx = ralloc_parent(var);
> > -            var->data.mode = ir_var_auto;
> >              var->data.location = 0;
> > -            var->constant_value = new(mem_ctx) ir_constant(num_vertices);
> > +            var->data.explicit_location = false;
> 
> Nitpick: With this change you are also changing slightly the option that
> was present before (use a constant) in addition to add the option to
> lower to an uniform. Not sure if it is worth to be mentioned though,
> feel free to ignore.

I am?  Before this patch, there was no option.  If the program being
linked contained a TCS, we would turn it into a constant.  If not, we
would leave it as a system value.

With this patch, my intention was to do the same behavior when no
options were set.  If ctx->Const.LowerTESPatchVerticesIn is set, we
turn it into a constant if there's a linked TCS (as before), and turn
it into a uniform otherwise (instead of a system value).

Did I miss something?
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