sqrt.c raw

   1  #include "libm.h"
   2  
   3  double sqrt(double x)
   4  {
   5  	union ldshape ux;
   6  	unsigned fpsr;
   7  	__asm__ ("fsqrt; fnstsw %%ax": "=t"(ux.f), "=a"(fpsr) : "0"(x));
   8  	if ((ux.i.m & 0x7ff) != 0x400)
   9  		return (double)ux.f;
  10  	/* Rounding to double would have encountered an exact halfway case.
  11  	   Adjust mantissa downwards if fsqrt rounded up, else upwards.
  12  	   (result of fsqrt could not have been exact) */
  13  	ux.i.m ^= (fpsr & 0x200) + 0x300;
  14  	return (double)ux.f;
  15  }
  16