From 89c9aa491a7cee97bf78a29cddbf0a25c902a671 Mon Sep 17 00:00:00 2001 From: Adhemerval Zanella Date: Thu, 10 May 2012 15:11:55 -0500 Subject: Fix for logb/logbf/logbl (bugs 13954/13955/13956) POSIX 2008 states that if the input for 'logb[f|l]' is a subnormal number it should be treated as if it were normalized. This means the implementation should calculate the log2 of the mantissa and add it to the subnormal exponent (-126 for float and -1022 for double and IBM long double). This patch takes care of that. --- sysdeps/ieee754/ldbl-128ibm/s_logbl.c | 35 +++++++++++++++++++++-------------- 1 file changed, 21 insertions(+), 14 deletions(-) (limited to 'sysdeps/ieee754/ldbl-128ibm/s_logbl.c') diff --git a/sysdeps/ieee754/ldbl-128ibm/s_logbl.c b/sysdeps/ieee754/ldbl-128ibm/s_logbl.c index f38b129..678b6ca 100644 --- a/sysdeps/ieee754/ldbl-128ibm/s_logbl.c +++ b/sysdeps/ieee754/ldbl-128ibm/s_logbl.c @@ -13,10 +13,6 @@ * ==================================================== */ -#if defined(LIBM_SCCS) && !defined(lint) -static char rcsid[] = "$NetBSD: $"; -#endif - /* * long double logbl(x) * IEEE 754 logb. Included to pass IEEE test suite. Not recommend. @@ -27,16 +23,27 @@ static char rcsid[] = "$NetBSD: $"; #include #include -long double __logbl(long double x) +long double +__logbl (long double x) { - int64_t lx,hx; - GET_LDOUBLE_WORDS64(hx,lx,x); - hx &= 0x7fffffffffffffffLL; /* high |x| */ - if((hx|(lx&0x7fffffffffffffffLL))==0) return -1.0/fabs(x); - if(hx>=0x7ff0000000000000LL) return x*x; - if((hx>>=52)==0) /* IEEE 754 logb */ - return -1022.0; - else - return (long double) (hx-0x3ff); + int64_t lx, hx, rhx; + + GET_LDOUBLE_WORDS64 (hx, lx, x); + hx &= 0x7fffffffffffffffLL; /* high |x| */ + if ((hx | (lx & 0x7fffffffffffffffLL)) == 0) + return -1.0 / fabs (x); + if (hx >= 0x7ff0000000000000LL) + return x * x; + if (__builtin_expect ((rhx = hx >> 52) == 0, 0)) + { + /* POSIX specifies that denormal number is treated as + though it were normalized. */ + int m1 = (hx == 0) ? 0 : __builtin_clzll (hx); + int m2 = (lx == 0) ? 0 : __builtin_clzll (lx); + int ma = (m1 == 0) ? m2 + 64 : m1; + return -1022.0 + (long double)(11 - ma); + } + return (long double) (rhx - 1023); } + long_double_symbol (libm, __logbl, logbl); -- cgit v1.1