xref: /freebsd-src/lib/libc/amd64/gen/flt_rounds.c (revision 559a218c9b257775fb249b67945fe4a05b7a6b9f)
1*479f8d22SDavid Schultz /*
2*479f8d22SDavid Schultz  * Written by J.T. Conklin, Apr 10, 1995
3*479f8d22SDavid Schultz  * Public domain.
4*479f8d22SDavid Schultz  */
5*479f8d22SDavid Schultz 
6*479f8d22SDavid Schultz #include <float.h>
7*479f8d22SDavid Schultz 
8*479f8d22SDavid Schultz static const int map[] = {
9*479f8d22SDavid Schultz 	1,	/* round to nearest */
10*479f8d22SDavid Schultz 	3,	/* round to zero */
11*479f8d22SDavid Schultz 	2,	/* round to negative infinity */
12*479f8d22SDavid Schultz 	0	/* round to positive infinity */
13*479f8d22SDavid Schultz };
14*479f8d22SDavid Schultz 
15*479f8d22SDavid Schultz int
__flt_rounds(void)16*479f8d22SDavid Schultz __flt_rounds(void)
17*479f8d22SDavid Schultz {
18*479f8d22SDavid Schultz 	int x;
19*479f8d22SDavid Schultz 
20*479f8d22SDavid Schultz         /* Assume that the x87 and the SSE unit agree on the rounding mode. */
21*479f8d22SDavid Schultz 	__asm("fnstcw %0" : "=m" (x));
22*479f8d22SDavid Schultz         return (map[(x >> 10) & 0x03]);
23*479f8d22SDavid Schultz }
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