PVS-Studio warning V801 for Crystalspace

static void TriSwap (csTriangle*& tr, const csTriangle tri,
                     bool in)
{
  if (in)
  {
    tr->a = tri.c;
    tr->b = tri.b;
    tr->c = tri.a;
  }
  else
  {
    tr->a = tri.a;
    tr->b = tri.b;
    tr->c = tri.c;
  }
  tr++;
}

a, b, c - int.

csTriangle is a class that has a copying constructor.

This suspicious code was found in Crystalspace project by PVS-Studio static code analyzer.
Warning message is:
V801 Decreased performance. It is better to redefine the second function argument as a reference. Consider replacing 'const .. tri' with 'const .. &tri'. libcrystalspace primitives.cpp 50

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