[Mesa-dev] [PATCH] glsl: restrict consumer stage condition to modify interpolation type

[Samuel Iglesias Gonsálvez]

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 at igalia.com>
---

This patch adds 2 regressions in dEQP:

dEQP-GLES31.functional.separate_shader.random.49
dEQP-GLES31.functional.separate_shader.random.106

The failure is returned by validation_io() because the number of inputs
and outputs does not match with this patch applied.

As the interpolation type is not modified in
varying_matches::record() when we don't know the consumer
(consumer_stage == -1, for example in some separate shader objects), we
don't pack them together because its packing class does not match.

As a result, some output packed varyings are in different varying slots
than the input ones. Due to that, we have a mismatch in the number of
inputs and outputs because we don't check how many varyings we have
inside of each varying slot ("packed:var0,var1...") nor their type.

The validation of packed varyings doesn't seem to be trivial
and this is a different issue than the one this patch fixes.

 src/glsl/link_varyings.cpp | 8 +++++---
 1 file 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
-- 
2.5.0