Vulkan: Treat varyings in a separable program as active

src/libANGLE/VaryingPacking.cpp

@@ -851,9 +851,20 @@ bool VaryingPacking::collectAndPackUserVaryings(gl::InfoLog &infoLog,
         // not active. GLES specs are a bit vague on whether it's allowed to only pack active
         // varyings, though GLES 3.1 spec section 11.1.2.1 says that "device-dependent
         // optimizations" may be used to make vertex shader outputs fit.
-        if ((input && output && output->staticUse) || isActiveBuiltInInput ||
-            isActiveBuiltInOutput ||
-            (isSeparableProgram && ((input && input->active) || (output && output->active))))
+        //
+        // When separable programs are linked, varyings at the separable program's boundary are
+        // treated as active. See section 7.4.1 in
+        // https://www.khronos.org/registry/OpenGL/specs/es/3.2/es_spec_3.2.pdf
+        bool matchedInputOutputStaticUse = (input && output && output->staticUse);
+        bool activeBuiltIn               = (isActiveBuiltInInput || isActiveBuiltInOutput);
+
+        // Separable program requirements
+        bool separableActiveInput  = (input && (input->active || !output));
+        bool separableActiveOutput = (output && (output->active || !input));
+        bool separableActiveVarying =
+            (isSeparableProgram && (separableActiveInput || separableActiveOutput));
+
+        if (matchedInputOutputStaticUse || activeBuiltIn || separableActiveVarying)
         {
             const sh::ShaderVariable *varying = output ? output : input;
 

src/tests/gl_tests/ProgramPipelineTest.cpp

@@ -650,6 +650,48 @@ void main()
     EXPECT_GL_ERROR(GL_INVALID_OPERATION);
 }
 
+// Test that a shader IO block varying with separable program links
+// successfully.
+TEST_P(ProgramPipelineTest31, VaryingIOBlockSeparableProgram)
+{
+    // Only the Vulkan backend supports PPOs
+    ANGLE_SKIP_TEST_IF(!IsVulkan());
+    ANGLE_SKIP_TEST_IF(!IsGLExtensionEnabled("GL_EXT_shader_io_blocks"));
+
+    constexpr char kVS[] =
+        R"(#version 310 es
+        #extension GL_EXT_shader_io_blocks : require
+
+        precision highp float;
+        in vec4 inputAttribute;
+        out Block_inout { vec4 value; } user_out;
+
+        void main()
+        {
+            gl_Position    = inputAttribute;
+            user_out.value = vec4(4.0, 5.0, 6.0, 7.0);
+        })";
+
+    constexpr char kFS[] =
+        R"(#version 310 es
+        #extension GL_EXT_shader_io_blocks : require
+
+        precision highp float;
+        layout(location = 0) out mediump vec4 color;
+        in Block_inout { vec4 value; } user_in;
+
+        void main()
+        {
+            color = vec4(1, 0, 0, 1);
+        })";
+
+    bindProgramPipeline(kVS, kFS);
+
+    drawQuadWithPPO("inputAttribute", 0.5f, 1.0f);
+    ASSERT_GL_NO_ERROR();
+    EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::red);
+}
+
 GTEST_ALLOW_UNINSTANTIATED_PARAMETERIZED_TEST(ProgramPipelineTest);
 ANGLE_INSTANTIATE_TEST_ES3_AND_ES31(ProgramPipelineTest);