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| | #include <math.h>
long double remquol(long double x, long double y, int *quo)
{
signed char *cx = (void *)&x, *cy = (void *)&y;
/* By ensuring that addresses of x and y cannot be discarded,
* this empty asm guides GCC into representing extraction of
* their sign bits as memory loads rather than making x and y
* not-address-taken internally and using bitfield operations,
* which in the end wouldn't work out, as extraction from FPU
* registers needs to go through memory anyway. This way GCC
* should manage to use incoming stack slots without spills. */
__asm__ ("" :: "X"(cx), "X"(cy));
long double t = x;
unsigned fpsr;
do __asm__ ("fprem1; fnstsw %%ax" : "+t"(t), "=a"(fpsr) : "u"(y));
while (fpsr & 0x400);
/* C0, C1, C3 flags in x87 status word carry low bits of quotient:
* 15 14 13 12 11 10 9 8
* . C3 . . . C2 C1 C0
* . b1 . . . 0 b0 b2 */
unsigned char i = fpsr >> 8;
i = i>>4 | i<<4;
/* i[5:2] is now {b0 b2 ? b1}. Retrieve {0 b2 b1 b0} via
* in-register table lookup. */
unsigned qbits = 0x7575313164642020 >> (i & 60);
qbits &= 7;
*quo = (cx[9]^cy[9]) < 0 ? -qbits : qbits;
return t;
}
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