HLSL: Disambiguate between struct function parameters

src/compiler/translator/UtilsHLSL.cpp

@@ -455,12 +455,21 @@ TString DisambiguateFunctionName(const TIntermSequence *parameters)
     for (auto parameter : *parameters)
     {
         const TType &paramType = parameter->getAsTyped()->getType();
-        // Disambiguation is needed for float2x2 and float4 parameters. These are the only parameter
-        // types that HLSL thinks are identical. float2x3 and float3x2 are different types, for
-        // example. Other parameter types are not added to function names to avoid making function
-        // names longer.
+        // Parameter types are only added to function names if they are ambiguous according to the
+        // native HLSL compiler. Other parameter types are not added to function names to avoid
+        // making function names longer.
         if (paramType.getObjectSize() == 4 && paramType.getBasicType() == EbtFloat)
         {
+            // Disambiguation is needed for float2x2 and float4 parameters. These are the only
+            // built-in types that HLSL thinks are identical. float2x3 and float3x2 are different
+            // types, for example.
+            disambiguatingString += "_" + TypeString(paramType);
+        }
+        else if (paramType.getBasicType() == EbtStruct)
+        {
+            // Disambiguation is needed for struct parameters, since HLSL thinks that structs with
+            // the same fields but a different name are identical.
+            ASSERT(paramType.getStruct()->name() != "");
             disambiguatingString += "_" + TypeString(paramType);
         }
     }

src/tests/gl_tests/GLSLTest.cpp

@@ -3133,6 +3133,30 @@ TEST_P(GLSLTest, VariableHidesUserDefinedFunctionAfterInitializer)
     EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::green);
 }
 
+// Test that structs with identical members are not ambiguous as function arguments.
+TEST_P(GLSLTest, StructsWithSameMembersDisambiguatedByName)
+{
+    const std::string &fragmentShader =
+        "precision mediump float;\n"
+        "uniform float u_zero;\n"
+        "struct S { float foo; };\n"
+        "struct S2 { float foo; };\n"
+        "float get(S s) { return s.foo + u_zero; }\n"
+        "float get(S2 s2) { return 0.25 + s2.foo + u_zero; }\n"
+        "void main()\n"
+        "{\n"
+        "    S s;\n"
+        "    s.foo = 0.5;\n"
+        "    S2 s2;\n"
+        "    s2.foo = 0.25;\n"
+        "    gl_FragColor = vec4(0.0, get(s) + get(s2), 0.0, 1.0);\n"
+        "}\n";
+
+    ANGLE_GL_PROGRAM(program, mSimpleVSSource, fragmentShader);
+    drawQuad(program.get(), "inputAttribute", 0.5f);
+    EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::green);
+}
+
 // Use this to select which configurations (e.g. which renderer, which GLES major version) these tests should be run against.
 ANGLE_INSTANTIATE_TEST(GLSLTest,
                        ES2_D3D9(),