PVS-Studio warning V656 for Doom3

uint AltOp::fixedLength()
{
  uint l1 = exp1->fixedLength();
  uint l2 = exp1->fixedLength();

  if (l1 != l2 || l1 == ~0u)
    return ~0;

  return l1;
}

This suspicious code was found in Doom3 project by PVS-Studio static code analyzer.
Warning message is:
V656 Variables are initialized through the call to the same function. It's probably an error or un-optimized code. Consider inspecting the 'exp1->fixedLength()' expression. actions.cc 391

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