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 lrint_slow(double x)41static 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 lrint(double x)54long 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 lrint(double x)68long lrint(double x) 69 { 70 return rint(x); 71 } 72 #endif 73