On Thu, 2017-06-22 at 09:27 +1000, Timothy Arceri wrote:
>
> On 22/06/17 02:41, Juan A. Suarez Romero wrote:
> > On Wed, 2017-06-21 at 20:24 +1000, Timothy Arceri wrote:
> > > On 21/06/17 18:13, Juan A. Suarez Romero wrote:
> > > > link_xfb_stride_layout_qualifiers() can be called multiple times, and
> > > > each time we call prog->TransformFeedback.BufferStride is reset to 0.
> > > >
> > > > Thus it is loosing the values set in previous call.
> > > >
> > > > Do not perform such reset.
> > > >
> > > > Fixes:
> > > > KHR-GL45.enhanced_layouts.xfb_stride_of_empty_list
> > > > KHR-GL45.enhanced_layouts.xfb_stride_of_empty_list_and_api
> > > >
> > > > Signed-off-by: Juan A. Suarez Romero <jasua...@igalia.com>
> > > > ---
> > > > src/compiler/glsl/linker.cpp | 4 ----
> > > > 1 file changed, 4 deletions(-)
> > > >
> > > > diff --git a/src/compiler/glsl/linker.cpp b/src/compiler/glsl/linker.cpp
> > > > index adfa3b7b1d..1fe0ccc496 100644
> > > > --- a/src/compiler/glsl/linker.cpp
> > > > +++ b/src/compiler/glsl/linker.cpp
> > > > @@ -1623,10 +1623,6 @@ link_xfb_stride_layout_qualifiers(struct
> > > > gl_context *ctx,
> > > > struct gl_shader **shader_list,
> > > > unsigned num_shaders)
> > > > {
> > > > - for (unsigned i = 0; i < MAX_FEEDBACK_BUFFERS; i++) {
> > > > - prog->TransformFeedback.BufferStride[i] = 0;
> > > > - }
> > >
> > > I think this probably needs to be moved rather than just deleted. I
> > > think the idea is to reset things to 0 in case we are re-linking an
> > > existing program with different shaders attached.
> > >
> >
> > Checking how this was done prior the refactoring in 4d65f68 (mesa/glsl:
> > move TransformFeedbackBufferStride to gl_shader), actually the reset
> > should be done if the new shaders provide an explicit xfb_stride.
> > Otherwise we should kept the old value.
> >
>
> No, that's not how it worked. The related change in 4d65f68 was:
>
> for (unsigned i = 0; i < MAX_FEEDBACK_BUFFERS; i++) {
> - linked_shader->info.TransformFeedback.BufferStride[i] = 0;
> + prog->TransformFeedback.BufferStride[i] = 0;
> }
>
What I meant is that prog->TransformFeedback.BufferStride was not
reset, but liked_shader->info.TransformFeedback.BufferStride.
And prog->TransformFeedback.BufferStride changed if the shader had an
explicit stride.
> There was no check previously we just reset everything.
>
> The problem is that previously each stage had its own copy of a
> BufferStride array. There was no need for this as xfb only applies to
> the last stage in the pipeline before the fragment shader.
>
> 4d65f68 changed it so that we share a single BufferStride array across
> the program instead, this allowed simplifications elsewhere and reduced
> the amount of data needed for shader cache. I assume the issue is that
> if we have a fragment shader attached then the array would get
> incorrectly reset.
>
Thanks for the explanation. I think I better understand the situation.
> Please see my reply to v2 for a suggested fix. Please let me know if
> that doesn't fix it.
>
>
Sure.
J.A.
> > I'm sending a new version.
> >
> >
> > > > -
> > > > for (unsigned i = 0; i < num_shaders; i++) {
> > > > struct gl_shader *shader = shader_list[i];
> > > >
> > > >
> > >
> > >
>
>
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