forked from pool/glibc
Andreas Schwab
006d01ca2c
- nextafterl-ibm-ldouble.patch: Correct IBM long double nextafterl (bnc#871637, BZ #16739) OBS-URL: https://build.opensuse.org/request/show/228849 OBS-URL: https://build.opensuse.org/package/show/Base:System/glibc?expand=0&rev=357
117 lines
4.7 KiB
Diff
117 lines
4.7 KiB
Diff
2014-04-02 Alan Modra <amodra@gmail.com>
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[BZ #16739]
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* sysdeps/ieee754/ldbl-128ibm/s_nextafterl.c (__nextafterl): Correct
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output when value is near a power of two. Use int64_t for lx and
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remove casts. Use decimal rather than hex exponent constants.
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Don't use long double multiplication when double will suffice.
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* math/libm-test.inc (nextafter_test_data): Add tests.
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Index: glibc-2.19/math/libm-test.inc
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===================================================================
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--- glibc-2.19.orig/math/libm-test.inc
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+++ glibc-2.19/math/libm-test.inc
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@@ -10528,6 +10528,14 @@ static const struct test_ff_f_data nexta
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// XXX Enable once gcc is fixed.
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//TEST_ff_f (nextafter, 0x0.00000040000000000000p-16385L, -0.1L, 0x0.0000003ffffffff00000p-16385L),
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#endif
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+#if defined TEST_LDOUBLE && LDBL_MANT_DIG == 106
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+ TEST_ff_f (nextafter, 1.0L, -10.0L, 1.0L-0x1p-106L, NO_EXCEPTION),
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+ TEST_ff_f (nextafter, 1.0L, 10.0L, 1.0L+0x1p-105L, NO_EXCEPTION),
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+ TEST_ff_f (nextafter, 1.0L-0x1p-106L, 10.0L, 1.0L, NO_EXCEPTION),
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+ TEST_ff_f (nextafter, -1.0L, -10.0L, -1.0L-0x1p-105L, NO_EXCEPTION),
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+ TEST_ff_f (nextafter, -1.0L, 10.0L, -1.0L+0x1p-106L, NO_EXCEPTION),
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+ TEST_ff_f (nextafter, -1.0L+0x1p-106L, -10.0L, -1.0L, NO_EXCEPTION),
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+#endif
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/* XXX We need the hexadecimal FP number representation here for further
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tests. */
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Index: glibc-2.19/sysdeps/ieee754/ldbl-128ibm/s_nextafterl.c
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===================================================================
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--- glibc-2.19.orig/sysdeps/ieee754/ldbl-128ibm/s_nextafterl.c
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+++ glibc-2.19/sysdeps/ieee754/ldbl-128ibm/s_nextafterl.c
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@@ -30,8 +30,7 @@ static char rcsid[] = "$NetBSD: $";
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long double __nextafterl(long double x, long double y)
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{
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- int64_t hx,hy,ihx,ihy;
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- uint64_t lx;
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+ int64_t hx, hy, ihx, ihy, lx;
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double xhi, xlo, yhi;
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ldbl_unpack (x, &xhi, &xlo);
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@@ -76,19 +75,28 @@ long double __nextafterl(long double x,
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u = math_opt_barrier (x);
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x -= __LDBL_DENORM_MIN__;
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if (ihx < 0x0360000000000000LL
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- || (hx > 0 && (int64_t) lx <= 0)
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- || (hx < 0 && (int64_t) lx > 1)) {
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+ || (hx > 0 && lx <= 0)
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+ || (hx < 0 && lx > 1)) {
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u = u * u;
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math_force_eval (u); /* raise underflow flag */
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}
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return x;
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}
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- if (ihx < 0x06a0000000000000LL) { /* ulp will denormal */
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- INSERT_WORDS64 (yhi, hx & (0x7ffLL<<52));
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- u = yhi;
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- u *= 0x1.0000000000000p-105L;
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+ /* If the high double is an exact power of two and the low
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+ double is the opposite sign, then 1ulp is one less than
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+ what we might determine from the high double. Similarly
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+ if X is an exact power of two, and positive, because
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+ making it a little smaller will result in the exponent
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+ decreasing by one and normalisation of the mantissa. */
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+ if ((hx & 0x000fffffffffffffLL) == 0
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+ && ((lx != 0 && (hx ^ lx) < 0)
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+ || (lx == 0 && hx >= 0)))
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+ ihx -= 1LL << 52;
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+ if (ihx < (106LL << 52)) { /* ulp will denormal */
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+ INSERT_WORDS64 (yhi, ihx & (0x7ffLL<<52));
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+ u = yhi * 0x1p-105;
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} else {
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- INSERT_WORDS64 (yhi, (hx & (0x7ffLL<<52))-(0x069LL<<52));
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+ INSERT_WORDS64 (yhi, (ihx & (0x7ffLL<<52))-(105LL<<52));
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u = yhi;
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}
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return x - u;
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@@ -103,8 +111,8 @@ long double __nextafterl(long double x,
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u = math_opt_barrier (x);
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x += __LDBL_DENORM_MIN__;
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if (ihx < 0x0360000000000000LL
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- || (hx > 0 && (int64_t) lx < 0 && lx != 0x8000000000000001LL)
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- || (hx < 0 && (int64_t) lx >= 0)) {
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+ || (hx > 0 && lx < 0 && lx != 0x8000000000000001LL)
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+ || (hx < 0 && lx >= 0)) {
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u = u * u;
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math_force_eval (u); /* raise underflow flag */
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}
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@@ -112,12 +120,21 @@ long double __nextafterl(long double x,
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x = -0.0L;
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return x;
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}
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- if (ihx < 0x06a0000000000000LL) { /* ulp will denormal */
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- INSERT_WORDS64 (yhi, hx & (0x7ffLL<<52));
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- u = yhi;
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- u *= 0x1.0000000000000p-105L;
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+ /* If the high double is an exact power of two and the low
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+ double is the opposite sign, then 1ulp is one less than
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+ what we might determine from the high double. Similarly
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+ if X is an exact power of two, and negative, because
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+ making it a little larger will result in the exponent
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+ decreasing by one and normalisation of the mantissa. */
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+ if ((hx & 0x000fffffffffffffLL) == 0
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+ && ((lx != 0 && (hx ^ lx) < 0)
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+ || (lx == 0 && hx < 0)))
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+ ihx -= 1LL << 52;
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+ if (ihx < (106LL << 52)) { /* ulp will denormal */
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+ INSERT_WORDS64 (yhi, ihx & (0x7ffLL<<52));
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+ u = yhi * 0x1p-105;
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} else {
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- INSERT_WORDS64 (yhi, (hx & (0x7ffLL<<52))-(0x069LL<<52));
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+ INSERT_WORDS64 (yhi, (ihx & (0x7ffLL<<52))-(105LL<<52));
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u = yhi;
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}
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return x + u;
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