v3d: we always have at least one output segment

If we program an output size of 0 the simulator asserts. This was
not a problem until now because our VS would always have to
emit fixed function outputs, however, now that it can be paired
with a GS we can end up with a VS shader that no longer emits
any outputs.

Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>

diff --git a/src/broadcom/compiler/v3d_nir_lower_io.c b/src/broadcom/compiler/v3d_nir_lower_io.c
index 3c9279a2fee72f6e782a946919a82a895ad4071b..9b7db65db7e22561a8ea237ccee0125c97894519 100644 (file)
--- a/src/broadcom/compiler/v3d_nir_lower_io.c
+++ b/src/broadcom/compiler/v3d_nir_lower_io.c
@@ -378,7 +378,7 @@ v3d_nir_setup_vpm_layout_vs(struct v3d_compile *c,
 
         state->varyings_vpm_offset = vpm_offset;
 
-        c->vpm_output_size = vpm_offset + c->vs_key->num_used_outputs;
+        c->vpm_output_size = MAX2(1, vpm_offset + c->vs_key->num_used_outputs);
 }
 
 static void