diff options
Diffstat (limited to 'sysdeps/ieee754/ldbl-128ibm/s_nextafterl.c')
| -rw-r--r-- | sysdeps/ieee754/ldbl-128ibm/s_nextafterl.c | 49 |
1 files changed, 33 insertions, 16 deletions
diff --git a/sysdeps/ieee754/ldbl-128ibm/s_nextafterl.c b/sysdeps/ieee754/ldbl-128ibm/s_nextafterl.c index 30b1540..bf57cb8 100644 --- a/sysdeps/ieee754/ldbl-128ibm/s_nextafterl.c +++ b/sysdeps/ieee754/ldbl-128ibm/s_nextafterl.c @@ -30,8 +30,7 @@ static char rcsid[] = "$NetBSD: $"; long double __nextafterl(long double x, long double y) { - int64_t hx,hy,ihx,ihy; - uint64_t lx; + int64_t hx, hy, ihx, ihy, lx; double xhi, xlo, yhi; ldbl_unpack (x, &xhi, &xlo); @@ -79,19 +78,28 @@ long double __nextafterl(long double x, long double y) u = math_opt_barrier (x); x -= __LDBL_DENORM_MIN__; if (ihx < 0x0360000000000000LL - || (hx > 0 && (int64_t) lx <= 0) - || (hx < 0 && (int64_t) lx > 1)) { + || (hx > 0 && lx <= 0) + || (hx < 0 && lx > 1)) { u = u * u; math_force_eval (u); /* raise underflow flag */ } return x; } - if (ihx < 0x06a0000000000000LL) { /* ulp will denormal */ - INSERT_WORDS64 (yhi, hx & (0x7ffLL<<52)); - u = yhi; - u *= 0x1.0000000000000p-105L; + /* If the high double is an exact power of two and the low + double is the opposite sign, then 1ulp is one less than + what we might determine from the high double. Similarly + if X is an exact power of two, and positive, because + making it a little smaller will result in the exponent + decreasing by one and normalisation of the mantissa. */ + if ((hx & 0x000fffffffffffffLL) == 0 + && ((lx != 0 && (hx ^ lx) < 0) + || (lx == 0 && hx >= 0))) + ihx -= 1LL << 52; + if (ihx < (106LL << 52)) { /* ulp will denormal */ + INSERT_WORDS64 (yhi, ihx & (0x7ffLL<<52)); + u = yhi * 0x1p-105; } else { - INSERT_WORDS64 (yhi, (hx & (0x7ffLL<<52))-(0x069LL<<52)); + INSERT_WORDS64 (yhi, (ihx & (0x7ffLL<<52))-(105LL<<52)); u = yhi; } return x - u; @@ -109,8 +117,8 @@ long double __nextafterl(long double x, long double y) u = math_opt_barrier (x); x += __LDBL_DENORM_MIN__; if (ihx < 0x0360000000000000LL - || (hx > 0 && (int64_t) lx < 0 && lx != 0x8000000000000001LL) - || (hx < 0 && (int64_t) lx >= 0)) { + || (hx > 0 && lx < 0 && lx != 0x8000000000000001LL) + || (hx < 0 && lx >= 0)) { u = u * u; math_force_eval (u); /* raise underflow flag */ } @@ -118,12 +126,21 @@ long double __nextafterl(long double x, long double y) x = -0.0L; return x; } - if (ihx < 0x06a0000000000000LL) { /* ulp will denormal */ - INSERT_WORDS64 (yhi, hx & (0x7ffLL<<52)); - u = yhi; - u *= 0x1.0000000000000p-105L; + /* If the high double is an exact power of two and the low + double is the opposite sign, then 1ulp is one less than + what we might determine from the high double. Similarly + if X is an exact power of two, and negative, because + making it a little larger will result in the exponent + decreasing by one and normalisation of the mantissa. */ + if ((hx & 0x000fffffffffffffLL) == 0 + && ((lx != 0 && (hx ^ lx) < 0) + || (lx == 0 && hx < 0))) + ihx -= 1LL << 52; + if (ihx < (106LL << 52)) { /* ulp will denormal */ + INSERT_WORDS64 (yhi, ihx & (0x7ffLL<<52)); + u = yhi * 0x1p-105; } else { - INSERT_WORDS64 (yhi, (hx & (0x7ffLL<<52))-(0x069LL<<52)); + INSERT_WORDS64 (yhi, (ihx & (0x7ffLL<<52))-(105LL<<52)); u = yhi; } return x + u; |