mingw-w64-crt/math/signbit.c

/**
 * This file has no copyright assigned and is placed in the Public Domain.
 * This file is part of the w64 mingw-runtime package.
 * No warranty is given; refer to the file DISCLAIMER.PD within this package.
 */
#define __FP_SIGNBIT  0x0200

int __signbit (double x);

int __signbit (double x) {
  unsigned short sw;
  __asm__ __volatile__ ("fxam; fstsw %%ax;"
	   : "=a" (sw)
	   : "t" (x) );
  return (sw & __FP_SIGNBIT) != 0;
}

#undef signbit
int __attribute__ ((alias ("__signbit"))) signbit (double);