PVS-Studio warning V610 for Snes9x

static void DSP1_Parameter (....)
{
  int16  C;
  ....
  if (C == -32768)
  {
    C >>= 1;
    E++;
  }
  ....
}

This suspicious code was found in Snes9x project by PVS-Studio static code analyzer.
Warning message is:
V610 Unspecified behavior. Check the shift operator '>>=. The left operand 'C' is negative. dsp1.cpp 808

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