v3d: handle writes to gl_Layer from geometry shaders

When geometry shaders write a value to gl_Layer that doesn't correspond to
an existing layer in the target framebuffer the rendering behavior is
undefined according to the spec, however, there are CTS tests that trigger
this scenario on purpose, probably to ensure that nothing terrible happens.

For V3D, this situation is problematic because the binner uses the layer
index to select the offset to write into the tile state data, and we only
allocate tile state for MAX2(num_layers, 1), so we want to make sure we
don't produce values that would lead to out of bounds writes. The simulator
has an assert to catch this, although we haven't observed issues in actual
hardware it is probably best to play safe.

Reviewed-by: Alejandro Piñeiro <[email protected]>

1 files changed, 8 insertions, 0 deletions

diff --git a/src/gallium/drivers/v3d/v3d_uniforms.c b/src/gallium/drivers/v3d/v3d_uniforms.c
index c94f6be4b76..ab57880f06f 100644
--- a/src/gallium/drivers/v3d/v3d_uniforms.c
+++ b/src/gallium/drivers/v3d/v3d_uniforms.c
@@ -373,6 +373,10 @@ v3d_write_uniforms(struct v3d_context *v3d, struct v3d_job *job,
                                          v3d->compute_shared_memory, 0);
                         break;
 
+                case QUNIFORM_FB_LAYERS:
+                        cl_aligned_u32(&uniforms, job->num_layers);
+                        break;
+
                 default:
                         assert(quniform_contents_is_texture_p0(uinfo->contents[i]));
 
@@ -465,6 +469,10 @@ v3d_set_shader_uniform_dirty_flags(struct v3d_compiled_shader *shader)
                         /* Compute always recalculates uniforms. */
                         break;
 
+                case QUNIFORM_FB_LAYERS:
+                        dirty |= VC5_DIRTY_FRAMEBUFFER;
+                        break;
+
                 default:
                         assert(quniform_contents_is_texture_p0(shader->prog_data.base->uniforms.contents[i]));
                         dirty |= VC5_DIRTY_FRAGTEX | VC5_DIRTY_VERTTEX |