diff options
Diffstat (limited to 'sysdeps/ieee754/ldbl-128ibm/s_logbl.c')
| -rw-r--r-- | sysdeps/ieee754/ldbl-128ibm/s_logbl.c | 19 |
1 files changed, 15 insertions, 4 deletions
diff --git a/sysdeps/ieee754/ldbl-128ibm/s_logbl.c b/sysdeps/ieee754/ldbl-128ibm/s_logbl.c index da8d71bdec..22e5fc24c0 100644 --- a/sysdeps/ieee754/ldbl-128ibm/s_logbl.c +++ b/sysdeps/ieee754/ldbl-128ibm/s_logbl.c @@ -26,22 +26,33 @@ long double __logbl (long double x) { - int64_t hx, rhx; - double xhi; + int64_t hx, hxs, rhx; + double xhi, xlo; - xhi = ldbl_high (x); + ldbl_unpack (x, &xhi, &xlo); EXTRACT_WORDS64 (hx, xhi); + hxs = hx; hx &= 0x7fffffffffffffffLL; /* high |x| */ if (hx == 0) return -1.0 / fabs (x); if (hx >= 0x7ff0000000000000LL) return x * x; - if (__builtin_expect ((rhx = hx >> 52) == 0, 0)) + if (__glibc_unlikely ((rhx = hx >> 52) == 0)) { /* POSIX specifies that denormal number is treated as though it were normalized. */ rhx -= __builtin_clzll (hx) - 12; } + else if ((hx & 0x000fffffffffffffLL) == 0) + { + /* If the high part is a power of 2, and the low part is nonzero + with the opposite sign, the low part affects the + exponent. */ + int64_t lx; + EXTRACT_WORDS64 (lx, xlo); + if ((hxs ^ lx) < 0 && (lx & 0x7fffffffffffffffLL) != 0) + rhx--; + } return (long double) (rhx - 1023); } #ifndef __logbl |