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Creating fastest Mul31

Hello, all.
I am interested what would be fastest implementation of the following multiplication:

#define Mul31(x,y) ((int32)(((int64)(x) * (y)) >> 31))

obviously, int32 and int64 are signed 32 and 64 integers.

Currently i am using: 
inline int32 Mul31(int32 x, int32 y)
{
  register int hi_prod, lo_prod, result;
  asm
  {
    mullw lo_prod, x, y
    srwi lo_prod, lo_prod, 31

    mulhw hi_prod, x, y
    slwi hi_prod, hi_prod, 1

    or result, hi_prod, lo_prod;
  }
  return result;
}


Is it possible to make it faster?
Target CPUs are PPC G4 and G5, and compiler are gcc 3.3 and 4.x
Thank you in advance.

--
Sincerely,
	Rustam Muginov

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