HLSL bug with const parameters and loops (tested with fxc from 7.0, 8.0, 8.1 Windows SDK)

Input

struct PS_INPUT 
{
    float4 Pos : VS_OUT_POSITION; 
};

// removing "const" fixes the problem
float4 Function(const float4 value)
{
    return value;
}

float4 main(PS_INPUT IN) : SV_Target
{
    float4 unused1 = Function(IN.Pos); // removing this fixes the problem

    float4 result = 0.0;

    for (float x = -4; x <= 4; x++)
    {
        float4 pos = IN.Pos - 1;

        float4 sample = Function(pos);

        float4 unused2 = sample/1.0; // by removing this, the compiler collapses the loop => correct result

        result += sample;
    }

    return result;
}

Output

ps_5_0
dcl_globalFlags refactoringAllowed
dcl_input_ps linear v0.xyzw
dcl_output o0.xyzw
dcl_temps 3
mov r0.xyzw, v0.xyzw                                                     // IN.Pos
mov r1.xyzw, l(0,0,0,0)
mov r2.x, l(-4.000000)
loop
  lt r2.y, l(4.000000), r2.x
  breakc_nz r2.y
  add r0.xyzw, r0.xyzw, l(-1.000000, -1.000000, -1.000000, -1.000000)    // repeatedly decremented!
  add r1.xyzw, r0.xyzw, r1.xyzw
  add r2.x, r2.x, l(1.000000)                                            // added to running sum (result)
endloop
mov o0.xyzw, r1.xyzw
ret