v3d/compiler: Fix sorting the gs and fs inputs

ntq_setup_fs_inputs and ntq_setup_gs_inputs sort the inputs according to
the driver location. This input array is then used to calculate the VPM
offset for the outputs in the previous stage. However, it wasn’t taking
into account variables that are packed into a single varying slot. In
that case they would have the same driver_location and are
distinguished by location_frac.

This patch makes it additionally sort by location_frac when the driver
locations are equal. This can happen when the compiler packs varyings
that are sized less than vec4. Without this fix, when the VPM is used to
transmit data free-form between the stages (such as VS->GS) then it
would end up writing to inconsistent locations.

Fixes dEQP tests such as:
dEQP-GLES31.functional.primitive_bounding_box.lines.global_state.
vertex_geometry_fragment.default_framebuffer_bbox_equal

Fixes: 5d578c27cec ("v3d: add initial compiler plumbing for geometry shaders")
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Reviewed-by: Jose Maria Casanova Crespo <jmcasanova@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5787>

diff --git a/src/broadcom/compiler/nir_to_vir.c b/src/broadcom/compiler/nir_to_vir.c
index d95361731cb9339a57d9347133c5ecf1bae5daa1..8f568d4779ade6d76ccd3c2483fdfedbd84f3579 100644 (file)
--- a/src/broadcom/compiler/nir_to_vir.c
+++ b/src/broadcom/compiler/nir_to_vir.c
@@ -1460,6 +1460,9 @@ driver_location_compare(const void *in_a, const void *in_b)
         const nir_variable *const *a = in_a;
         const nir_variable *const *b = in_b;
 
+        if ((*a)->data.driver_location == (*b)->data.driver_location)
+                return (*a)->data.location_frac - (*b)->data.location_frac;
+
         return (*a)->data.driver_location - (*b)->data.driver_location;
 }