Constant fold compute shader local work group size

src/compiler/translator/ParseContext.cpp

@@ -1471,6 +1471,25 @@ TIntermTyped *TParseContext::parseVariableIdentifier(const TSourceLoc &location,
         const TConstantUnion *constArray = variable->getConstPointer();
         return intermediate.addConstantUnion(constArray, variable->getType(), location);
     }
+    else if (variable->getType().getQualifier() == EvqWorkGroupSize &&
+             mComputeShaderLocalSizeDeclared)
+    {
+        // gl_WorkGroupSize can be used to size arrays according to the ESSL 3.10.4 spec, so it
+        // needs to be added to the AST as a constant and not as a symbol.
+        sh::WorkGroupSize workGroupSize = getComputeShaderLocalSize();
+        TConstantUnion *constArray      = new TConstantUnion[3];
+        for (size_t i = 0; i < 3; ++i)
+        {
+            constArray[i].setUConst(static_cast<unsigned int>(workGroupSize[i]));
+        }
+
+        ASSERT(variable->getType().getBasicType() == EbtUInt);
+        ASSERT(variable->getType().getObjectSize() == 3);
+
+        TType type(variable->getType());
+        type.setQualifier(EvqConst);
+        return intermediate.addConstantUnion(constArray, type, location);
+    }
     else
     {
         return intermediate.addSymbol(variable->getUniqueId(), variable->getName(),

src/tests/compiler_tests/MalformedShader_test.cpp

@@ -3111,3 +3111,22 @@ TEST_F(MalformedFragmentShaderGLES31Test, OverqualifyingImageParameter)
         FAIL() << "Shader compilation failed, expecting success " << mInfoLog;
     }
 }
+
+// Test that work group size can be used to size arrays.
+// GLSL ES 3.10.4 section 7.1.3 Compute Shader Special Variables
+TEST_F(MalformedComputeShaderTest, WorkGroupSizeAsArraySize)
+{
+    const std::string &shaderString =
+        "#version 310 es\n"
+        "layout(local_size_x = 5, local_size_y = 3, local_size_z = 1) in;\n"
+        "void main()\n"
+        "{\n"
+        "    int[gl_WorkGroupSize.x] a = int[5](0, 0, 0, 0, 0);\n"
+        "    int[gl_WorkGroupSize.y] b = int[3](0, 0, 0);\n"
+        "    int[gl_WorkGroupSize.z] c = int[1](0);\n"
+        "}\n";
+    if (!compile(shaderString))
+    {
+        FAIL() << "Shader compilation failed, expecting success " << mInfoLog;
+    }
+}