| Message ID | 20140325022618.GF18201@bubble.grove.modra.org |
|---|---|
| State | New |
| Headers | show |
On Tue, 25 Mar 2014, Alan Modra wrote: > + TEST_ff_f (nextafter, 1.0L, -10.0L, 1.0L-0x1p-106L, NO_EXCEPTION), > + TEST_ff_f (nextafter, 1.0L, 10.0L, 1.0L+0x1p-105L, NO_EXCEPTION), > + TEST_ff_f (nextafter, 1.0L-0x1p-106L, 10.0L, 1.0L, NO_EXCEPTION), > + TEST_ff_f (nextafter, -1.0L, -10.0L, -1.0L-0x1p-105L, NO_EXCEPTION), > + TEST_ff_f (nextafter, -1.0L, 10.0L, -1.0L+0x1p-106L, NO_EXCEPTION), > + TEST_ff_f (nextafter, -1.0L+0x1p-106L, -10.0L, -1.0L, NO_EXCEPTION), You mean NO_INEXACT_EXCEPTION (NO_EXCEPTION makes no assertion about whether or not "inexact" is present; "inexact" has a different default from the other exceptions, following ISO C Annex F).
On Tue, Mar 25, 2014 at 12:13:08PM +0000, Joseph S. Myers wrote: > On Tue, 25 Mar 2014, Alan Modra wrote: > > > + TEST_ff_f (nextafter, 1.0L, -10.0L, 1.0L-0x1p-106L, NO_EXCEPTION), > > + TEST_ff_f (nextafter, 1.0L, 10.0L, 1.0L+0x1p-105L, NO_EXCEPTION), > > + TEST_ff_f (nextafter, 1.0L-0x1p-106L, 10.0L, 1.0L, NO_EXCEPTION), > > + TEST_ff_f (nextafter, -1.0L, -10.0L, -1.0L-0x1p-105L, NO_EXCEPTION), > > + TEST_ff_f (nextafter, -1.0L, 10.0L, -1.0L+0x1p-106L, NO_EXCEPTION), > > + TEST_ff_f (nextafter, -1.0L+0x1p-106L, -10.0L, -1.0L, NO_EXCEPTION), > > You mean NO_INEXACT_EXCEPTION (NO_EXCEPTION makes no assertion about > whether or not "inexact" is present; "inexact" has a different default > from the other exceptions, following ISO C Annex F). I deliberately did not choose NO_INEXACT_EXCEPTION, because nextafterl on IBM long double *does* set FE_INEXACT on some of these tests. The reason is the "x + u" or "x - u" operations inside nextafterl which use __gcc_qadd. As you know, __gcc_qadd spuriously sets FE_INEXACT. Also, as the description of IBM long double in the PowerPC64 ABI states, the "Extended precision" format * Does not support the IEEE status flags for overflow, underflow, and other conditions. These flag have no meaning in this format.
On 25-03-2014 10:15, Alan Modra wrote: > On Tue, Mar 25, 2014 at 12:13:08PM +0000, Joseph S. Myers wrote: >> On Tue, 25 Mar 2014, Alan Modra wrote: >> >>> + TEST_ff_f (nextafter, 1.0L, -10.0L, 1.0L-0x1p-106L, NO_EXCEPTION), >>> + TEST_ff_f (nextafter, 1.0L, 10.0L, 1.0L+0x1p-105L, NO_EXCEPTION), >>> + TEST_ff_f (nextafter, 1.0L-0x1p-106L, 10.0L, 1.0L, NO_EXCEPTION), >>> + TEST_ff_f (nextafter, -1.0L, -10.0L, -1.0L-0x1p-105L, NO_EXCEPTION), >>> + TEST_ff_f (nextafter, -1.0L, 10.0L, -1.0L+0x1p-106L, NO_EXCEPTION), >>> + TEST_ff_f (nextafter, -1.0L+0x1p-106L, -10.0L, -1.0L, NO_EXCEPTION), >> You mean NO_INEXACT_EXCEPTION (NO_EXCEPTION makes no assertion about >> whether or not "inexact" is present; "inexact" has a different default >> from the other exceptions, following ISO C Annex F). > I deliberately did not choose NO_INEXACT_EXCEPTION, because nextafterl > on IBM long double *does* set FE_INEXACT on some of these tests. The > reason is the "x + u" or "x - u" operations inside nextafterl which > use __gcc_qadd. As you know, __gcc_qadd spuriously sets FE_INEXACT. > Also, as the description of IBM long double in the PowerPC64 ABI > states, the "Extended precision" format > > * Does not support the IEEE status flags for overflow, underflow, and > other conditions. These flag have no meaning in this format. > If Joseph any more concerns, I'm ok with this patch.
On Thu, 27 Mar 2014, Adhemerval Zanella wrote:
> If Joseph any more concerns, I'm ok with this patch.
I have no further concerns with this patch.
diff --git a/math/libm-test.inc b/math/libm-test.inc index 5e50f0e..e97b18a 100644 --- a/math/libm-test.inc +++ b/math/libm-test.inc @@ -8312,6 +8312,14 @@ static const struct test_ff_f_data nextafter_test_data[] = // XXX Enable once gcc is fixed. //TEST_ff_f (nextafter, 0x0.00000040000000000000p-16385L, -0.1L, 0x0.0000003ffffffff00000p-16385L), #endif +#if defined TEST_LDOUBLE && LDBL_MANT_DIG == 106 + TEST_ff_f (nextafter, 1.0L, -10.0L, 1.0L-0x1p-106L, NO_EXCEPTION), + TEST_ff_f (nextafter, 1.0L, 10.0L, 1.0L+0x1p-105L, NO_EXCEPTION), + TEST_ff_f (nextafter, 1.0L-0x1p-106L, 10.0L, 1.0L, NO_EXCEPTION), + TEST_ff_f (nextafter, -1.0L, -10.0L, -1.0L-0x1p-105L, NO_EXCEPTION), + TEST_ff_f (nextafter, -1.0L, 10.0L, -1.0L+0x1p-106L, NO_EXCEPTION), + TEST_ff_f (nextafter, -1.0L+0x1p-106L, -10.0L, -1.0L, NO_EXCEPTION), +#endif /* XXX We need the hexadecimal FP number representation here for further tests. */ 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;