[Mesa-dev] [PATCH 30/53] mesa: don't always set _NEW_PROGRAM when linking

[Timothy Arceri]

On Tue, 2017-01-03 at 22:41 +0100, Marek Olšák wrote:
> On Tue, Jan 3, 2017 at 10:14 PM, Timothy Arceri
> <timothy.arceri at collabora.com> wrote:
> > On Tue, 2017-01-03 at 22:07 +0100, Marek Olšák wrote:
> > > On Tue, Jan 3, 2017 at 9:57 PM, Timothy Arceri
> > > <timothy.arceri at collabora.com> wrote:
> > > > On Tue, 2017-01-03 at 20:47 +0100, Marek Olšák wrote:
> > > > > On Tue, Jan 3, 2017 at 3:43 AM, Timothy Arceri
> > > > > <timothy.arceri at collabora.com> wrote:
> > > > > > We only need to set it when linking was successful and the
> > > > > > program
> > > > > > being linked is currently active.
> > > > > > 
> > > > > > The programs_in_use mask is just used as a flag for now but
> > > > > > in
> > > > > > a following patch we will use it to update the
> > > > > > CurrentProgram
> > > > > > array.
> > > > > > ---
> > > > > >  src/mesa/main/shaderapi.c | 22 +++++++++++++++++++++-
> > > > > >  1 file changed, 21 insertions(+), 1 deletion(-)
> > > > > > 
> > > > > > diff --git a/src/mesa/main/shaderapi.c
> > > > > > b/src/mesa/main/shaderapi.c
> > > > > > index 022afab..6c03dcb 100644
> > > > > > --- a/src/mesa/main/shaderapi.c
> > > > > > +++ b/src/mesa/main/shaderapi.c
> > > > > > @@ -1083,10 +1083,30 @@ _mesa_link_program(struct
> > > > > > gl_context
> > > > > > *ctx,
> > > > > > struct gl_shader_program *shProg)
> > > > > >        return;
> > > > > >     }
> > > > > > 
> > > > > > -   FLUSH_VERTICES(ctx, _NEW_PROGRAM);
> > > > > > +   unsigned programs_in_use = 0;
> > > > > > +   if (ctx->_Shader)
> > > > > > +      for (unsigned stage = 0; stage < MESA_SHADER_STAGES;
> > > > > > stage++) {
> > > > > > +         if (ctx->_Shader->CurrentProgram[stage] ==
> > > > > > shProg) {
> > > > > > +            programs_in_use |= 1 << stage;
> > > > > > +         }
> > > > > > +   }
> > > > > > 
> > > > > >     _mesa_glsl_link_shader(ctx, shProg);
> > > > > > 
> > > > > > +   /* From section 7.3 (Program Objects) of the OpenGL 4.5
> > > > > > spec:
> > > > > > +    *
> > > > > > +    *    "If LinkProgram or ProgramBinary successfully re-
> > > > > > links a
> > > > > > program
> > > > > > +    *     object that is active for any shader stage, then
> > > > > > the
> > > > > > newly generated
> > > > > > +    *     executable code will be installed as part of the
> > > > > > current
> > > > > > rendering
> > > > > > +    *     state for all shader stages where the program is
> > > > > > active.
> > > > > > +    *     Additionally, the newly generated executable
> > > > > > code is
> > > > > > made part of
> > > > > > +    *     the state of any program pipeline for all stages
> > > > > > where
> > > > > > the program
> > > > > > +    *     is attached."
> > > > > > +    */
> > > > > > +   if (shProg->data->LinkStatus && programs_in_use) {
> > > > > > +      FLUSH_VERTICES(ctx, _NEW_PROGRAM);
> > > > > > +   }
> > > > > 
> > > > > This doesn't seem correct. If the context has unflushed
> > > > > vertices,
> > > > > calling FLUSH_VERTICES after linking will use the new linked
> > > > > program
> > > > > instead of the previous program for which the vertices were
> > > > > submitted.
> > > > 
> > > > Your probably right but this doesn't make anything worse than
> > > > it
> > > > already is right?
> > > > 
> > > > Before this change we where always calling FLUSH_VERTICES(ctx,
> > > > _NEW_PROGRAM);
> > > 
> > > The useless flagging is a different issue.
> > > 
> > > FLUSH_VERTICES should be called before a state change, because it
> > > flushes draw calls that the driver hasn't even seen yet. After
> > > the
> > > driver processes those draw calls, _NEW_PROGRAM is set. That's
> > > how it
> > > works.
> > > 
> > > If you instead change a state and then call FLUSH_VERTICES, the
> > > previous unflushed draw calls will use the new state, which is
> > > incorrect.
> > 
> > But the state doesn't change just from linking does it? The new
> > programs won't be made current until glUseProgram() is called.
> 
> The GL state changes if the program is current and re-linked. (not
> sure if all of the internal Mesa state changes too)

Right but this patch only changes things so that FLUSH_VERTICES is not
called when the program is *not* current.

When glUseProgram (or the SSO equivalents) are called we should end up
in shaderapi.c:use_program() which does FLUSH_VERTICES(ctx,
_NEW_PROGRAM | _NEW_PROGRAM_CONSTANTS); if the program is not already
the current program and there is already a current program in use.

> 
> Marek
> _______________________________________________
> mesa-dev mailing list
> mesa-dev at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/mesa-dev