On Mon, 2016-11-28 at 18:59 -0800, Ian Romanick wrote:
> On 11/20/2016 05:28 AM, Timothy Arceri wrote:
> >
> > Now that we have a linked_stages bitfield we can use this
> > to check if the program is used at a later stage.
> >
> > This change is also required to be able to use gl_program
> > rather than gl_shader_program in the CurrentProgram array.
> > ---
> > src/mesa/main/pipelineobj.c | 17 +++++++----------
> > 1 file changed, 7 insertions(+), 10 deletions(-)
> >
> > diff --git a/src/mesa/main/pipelineobj.c
> > b/src/mesa/main/pipelineobj.c
> > index 35d416d..45131d2 100644
> > --- a/src/mesa/main/pipelineobj.c
> > +++ b/src/mesa/main/pipelineobj.c
> > @@ -730,30 +730,27 @@ program_stages_all_active(struct
> > gl_pipeline_object *pipe,
> > static bool
> > program_stages_interleaved_illegally(const struct
> > gl_pipeline_object *pipe)
> > {
> > - struct gl_shader_program *prev = NULL;
> > - unsigned i, j;
> > + unsigned prev_linked_stages = 0;
> >
> > /* Look for programs bound to stages: A -> B -> A, with any
> > intervening
> > * sequence of unrelated programs or empty stages.
> > */
> > - for (i = 0; i < MESA_SHADER_STAGES; i++) {
> > + for (unsigned i = 0; i < MESA_SHADER_STAGES; i++) {
> > struct gl_shader_program *cur = pipe->CurrentProgram[i];
> >
> > /* Empty stages anywhere in the pipe are OK */
> > - if (!cur || cur == prev)
> > + if (!cur || cur->data->linked_stages == prev_linked_stages)
>
> The previous 'cur == prev' check would prevent validation when, say,
> a
> program with a linked vertex shader and geometry shader were attached
> to
> a pipeline. Just looking at this line of code, it's not immediately
> obvious why the new check is equivalent. I'm guessing that code
> elsewhere generates an error if the application binds a programs with
> the same set of stages to a pipeline
>
> glGenProgramPipelines(1, &pipe);
> glGenPrograms(2, prog);
>
> // compile and link two programs that have a vertex & fragment
> // shader.
> // ...
>
> glBindProgramPipeline(pipe);
> glUseProgramStages(pipe, GL_VERTEX_SHADER_BIT, prog[0]);
> glUseProgramStages(pipe, GL_FRAGMENT_SHADER_BIT, prog[1]);
>
> In the existing code, this pipeline will get validated here (and
> fail).
> With the new code, it will not get validated here.
Your guess was correct. The check above this
one program_stages_all_active() ensures that all stages of a program
are active so we will always fail before validating interleaved stages
in the example you gave. Therefore cur->data->linked_stages ==
prev_linked_stages can only ever mean that we are looking at the same
program.
I could add a comment if you think it would help?
>
> >
> > continue;
> >
> > - if (prev) {
> > + if (prev_linked_stages) {
> > /* We've seen an A -> B transition; look at the rest of
> > the pipe
> > * to see if we ever see A again.
> > */
> > - for (j = i + 1; j < MESA_SHADER_STAGES; j++) {
> > - if (pipe->CurrentProgram[j] == prev)
> > - return true;
> > - }
> > + if (prev_linked_stages >> (i + 1))
> > + return true;
> > }
> >
> > - prev = cur;
> > + prev_linked_stages = cur->data->linked_stages;
> > }
> >
> > return false;
> >
>
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