1 #include <limits.h>
2 #include <fenv.h>
3 #include <math.h>
4 #include "libm.h"
5 6 /*
7 If the result cannot be represented (overflow, nan), then
8 lrint raises the invalid exception.
9 10 Otherwise if the input was not an integer then the inexact
11 exception is raised.
12 13 C99 is a bit vague about whether inexact exception is
14 allowed to be raised when invalid is raised.
15 (F.9 explicitly allows spurious inexact exceptions, F.9.6.5
16 does not make it clear if that rule applies to lrint, but
17 IEEE 754r 7.8 seems to forbid spurious inexact exception in
18 the ineger conversion functions)
19 20 So we try to make sure that no spurious inexact exception is
21 raised in case of an overflow.
22 23 If the bit size of long > precision of double, then there
24 cannot be inexact rounding in case the result overflows,
25 otherwise LONG_MAX and LONG_MIN can be represented exactly
26 as a double.
27 */
28 29 #if LONG_MAX < 1U<<53 && defined(FE_INEXACT)
30 #include <float.h>
31 #include <stdint.h>
32 #if FLT_EVAL_METHOD==0 || FLT_EVAL_METHOD==1
33 #define EPS DBL_EPSILON
34 #elif FLT_EVAL_METHOD==2
35 #define EPS LDBL_EPSILON
36 #endif
37 #ifdef __GNUC__
38 /* avoid stack frame in lrint */
39 __attribute__((noinline))
40 #endif
41 static long lrint_slow(double x)
42 {
43 #pragma STDC FENV_ACCESS ON
44 int e;
45 46 e = fetestexcept(FE_INEXACT);
47 x = rint(x);
48 if (!e && (x > LONG_MAX || x < LONG_MIN))
49 feclearexcept(FE_INEXACT);
50 /* conversion */
51 return x;
52 }
53 54 long lrint(double x)
55 {
56 uint32_t abstop = asuint64(x)>>32 & 0x7fffffff;
57 uint64_t sign = asuint64(x) & (1ULL << 63);
58 59 if (abstop < 0x41dfffff) {
60 /* |x| < 0x7ffffc00, no overflow */
61 double_t toint = asdouble(asuint64(1/EPS) | sign);
62 double_t y = x + toint - toint;
63 return (long)y;
64 }
65 return lrint_slow(x);
66 }
67 #else
68 long lrint(double x)
69 {
70 return rint(x);
71 }
72 #endif
73