sksl/shared/UniformMatrixResize.sksl

uniform float3x3 testMatrix3x3;
uniform half4 colorGreen, colorRed;

noinline float2x2 resizeMatrix() {
    return float2x2(testMatrix3x3);
}

half4 main(float2 coords) {
    return (resizeMatrix()           == float2x2(1, 2,
                                                 4, 5) &&
            float3x3(resizeMatrix()) == float3x3(1, 2, 0,
                                                 4, 5, 0,
                                                 0, 0, 1)) ? colorGreen : colorRed;
}