glsl: restrict consumer stage condition to modify interpolation type

Only modify interpolation type for integer-based varyings or when the
consumer is known and different than fragment shader.

If we are linking separate shader programs and the consumer is unknown,
the consumer could be added later and be a fragment shader. If we
modify the interpolation type in this case, we could read wrong
values in the fragment shader inputs, as shown in bug 93320.

Fixes the following CTS test:
   ES31-CTS.vertex_attrib_binding.advanced-bindingUpdate

Fixes the following dEQP tests:

dEQP-GLES31.functional.separate_shader.random.102
dEQP-GLES31.functional.separate_shader.random.111
dEQP-GLES31.functional.separate_shader.random.115
dEQP-GLES31.functional.separate_shader.random.17
dEQP-GLES31.functional.separate_shader.random.22
dEQP-GLES31.functional.separate_shader.random.23
dEQP-GLES31.functional.separate_shader.random.3
dEQP-GLES31.functional.separate_shader.random.32
dEQP-GLES31.functional.separate_shader.random.39
dEQP-GLES31.functional.separate_shader.random.64
dEQP-GLES31.functional.separate_shader.random.73
dEQP-GLES31.functional.separate_shader.random.91

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93320
Signed-off-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com>
Reviewed-by: Tapani Pälli <tapani.palli@intel.com>

1 files changed, 5 insertions, 3 deletions

diff --git a/src/glsl/link_varyings.cpp b/src/glsl/link_varyings.cpp
index 7cc5880..09f80d0 100644
--- a/src/glsl/link_varyings.cpp
+++ b/src/glsl/link_varyings.cpp
@@ -968,10 +968,12 @@ varying_matches::record(ir_variable *producer_var, ir_variable *consumer_var)
    }
 
    if ((consumer_var == NULL && producer_var->type->contains_integer()) ||
-       consumer_stage != MESA_SHADER_FRAGMENT) {
+       (consumer_stage != -1 && consumer_stage != MESA_SHADER_FRAGMENT)) {
       /* Since this varying is not being consumed by the fragment shader, its
-       * interpolation type varying cannot possibly affect rendering.  Also,
-       * this variable is non-flat and is (or contains) an integer.
+       * interpolation type varying cannot possibly affect rendering.
+       * Also, this variable is non-flat and is (or contains) an integer.
+       * If the consumer stage is unknown, don't modify the interpolation
+       * type as it could affect rendering later with separate shaders.
        *
        * lower_packed_varyings requires all integer varyings to flat,
        * regardless of where they appear.  We can trivially satisfy that