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Correct IBM long double nextafterl.

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Fix for values near a power of two, and some tidies.

	[BZ #16739]
	* sysdeps/ieee754/ldbl-128ibm/s_nextafterl.c (__nextafterl): Correct
	output when value is near a power of two.  Use int64_t for lx and
	remove casts.  Use decimal rather than hex exponent constants.
	Don't use long double multiplication when double will suffice.
	* math/libm-test.inc (nextafter_test_data): Add tests.
	* NEWS: Add 16739 and 16786 to bug list.
This commit is contained in:
Alan Modra
2014-04-02 13:46:19 +10:30
parent af6b17973c
commit b0abbc2103
4 changed files with 52 additions and 17 deletions
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49
sysdeps/ieee754/ldbl-128ibm/s_nextafterl.c
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@@ -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;