const float cPi = 3.14159265; // 3.14159274
const float4 ePi = float4(
	3.14159e-00,
	2.65358e-06,
	9.79323e-12,
	8.46264e-18
);

const float getPi_dp24() {
    float rPi;
    rPi = ePi[3] +
          ePi[2] +
          ePi[1] +
          ePi[0] ;
    return rPi;
}

const float getPi_dp18() {
    float rPi;
    rPi = ePi[2] +
          ePi[1] +
          ePi[0] ;
    return rPi;
}

const float getPi_dp12() {
    volatile float rPi;
    rPi = ePi[1] +
          ePi[0] ;
    return rPi;
}

float4 main( float4 unk1 : COLOR1, float4 unk2 : COLOR2 ) : COLOR0 {
    // arguments to main are 'uncertain', and so are not const-expression optimized away
    const float3 v1 = float3( 1, 1, 1 );
    float
	NL = unk1[0], NV = unk1[1],
	F = unk1[2],
	Df = unk1[3],
	G = unk2[0],
	Pi = getPi_dp24();
    float Si_1 = (F * Df * G);
    float Si_2 = (Pi * NL * NV);
    return float4( Si_1, Si_2, Si_1 / Si_2, 1 );
}