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Fix acosh (1) in round-downward mode (bug 16927).
According to C99 and C11 Annex F, acosh (1) should be +0 in all rounding modes. However, some implementations in glibc wrongly return -0 in round-downward mode (which is what you get if you end up computing log1p (-0), via 1 - 1 being -0 in round-downward mode). This patch fixes the problem implementations, by correcting the test for an exact 1 value in the ldbl-96 implementation to allow for the explicit high bit of the mantissa, and by inserting fabs instructions in the i386 implementations; tests of acosh are duly converted to ALL_RM_TEST. I believe all the other sysdeps/ieee754 implementations are already OK (I haven't checked the ia64 versions, but if buggy then that will be obvious from the results of test runs after this patch is in). Tested x86_64 and x86 and ulps updated accordingly. [BZ #16927] * sysdeps/i386/fpu/e_acosh.S (__ieee754_acosh): Use fabs on x-1 value. * sysdeps/i386/fpu/e_acoshf.S (__ieee754_acoshf): Likewise. * sysdeps/i386/fpu/e_acoshl.S (__ieee754_acoshl): Likewise. * sysdeps/ieee754/ldbl-96/e_acoshl.c (__ieee754_acoshl): Correct for explicit high bit of mantissa when testing for argument equal to 1. * math/libm-test.inc (acosh_test): Use ALL_RM_TEST. * sysdeps/i386/fpu/libm-test-ulps: Update. * sysdeps/x86_64/fpu/libm-test-ulps: Likewise.
This commit is contained in:
Joseph Myers
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0bf061d3e3
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12
ChangeLog
12
ChangeLog
@ -1,5 +1,17 @@
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2014-05-14 Joseph Myers <joseph@codesourcery.com>
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[BZ #16927]
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* sysdeps/i386/fpu/e_acosh.S (__ieee754_acosh): Use fabs on x-1
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value.
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* sysdeps/i386/fpu/e_acoshf.S (__ieee754_acoshf): Likewise.
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* sysdeps/i386/fpu/e_acoshl.S (__ieee754_acoshl): Likewise.
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* sysdeps/ieee754/ldbl-96/e_acoshl.c (__ieee754_acoshl): Correct
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for explicit high bit of mantissa when testing for argument equal
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to 1.
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* math/libm-test.inc (acosh_test): Use ALL_RM_TEST.
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* sysdeps/i386/fpu/libm-test-ulps: Update.
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* sysdeps/x86_64/fpu/libm-test-ulps: Likewise.
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[BZ #16516]
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* sysdeps/ieee754/dbl-64/s_erf.c (efx8): Remove variable.
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(__erf): Scale by 16 instead of 8 in potentially underflowing
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2
NEWS
2
NEWS
@ -17,7 +17,7 @@ Version 2.20
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16713, 16714, 16731, 16739, 16740, 16743, 16754, 16758, 16759, 16760,
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16770, 16786, 16789, 16791, 16799, 16800, 16815, 16823, 16824, 16831,
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16838, 16854, 16876, 16877, 16885, 16888, 16890, 16912, 16916, 16922,
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16932.
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16927, 16932.
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* The minimum Linux kernel version that this version of the GNU C Library
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can be used with is 2.6.32.
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@ -1792,9 +1792,7 @@ static const struct test_f_f_data acosh_test_data[] =
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static void
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acosh_test (void)
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{
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START (acosh, 0);
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RUN_TEST_LOOP_f_f (acosh, acosh_test_data, );
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END;
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ALL_RM_TEST (acosh, 0, acosh_test_data, RUN_TEST_LOOP_f_f, END);
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}
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static const struct test_f_f_data asin_test_data[] =
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@ -52,6 +52,7 @@ ENTRY(__ieee754_acosh)
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// 1 <= x <= 2 => y = log1p(x-1+sqrt(2*(x-1)+(x-1)^2))
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fsubl MO(one) // x-1 : log(2)
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fabs // acosh(1) is +0 in all rounding modes
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fld %st // x-1 : x-1 : log(2)
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fmul %st(1) // (x-1)^2 : x-1 : log(2)
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fadd %st(1) // x-1+(x-1)^2 : x-1 : log(2)
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@ -52,6 +52,7 @@ ENTRY(__ieee754_acoshf)
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// 1 <= x <= 2 => y = log1p(x-1+sqrt(2*(x-1)+(x-1)^2))
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fsubl MO(one) // x-1 : log(2)
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fabs // acosh(1) is +0 in all rounding modes
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fld %st // x-1 : x-1 : log(2)
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fmul %st(1) // (x-1)^2 : x-1 : log(2)
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fadd %st(1) // x-1+(x-1)^2 : x-1 : log(2)
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@ -59,6 +59,7 @@ ENTRY(__ieee754_acoshl)
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// 1 <= x <= 2 => y = log1p(x-1+sqrt(2*(x-1)+(x-1)^2))
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fsubl MO(one) // x-1 : log(2)
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fabs // acosh(1) is +0 in all rounding modes
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fld %st // x-1 : x-1 : log(2)
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fmul %st(1) // (x-1)^2 : x-1 : log(2)
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fadd %st(1) // x-1+(x-1)^2 : x-1 : log(2)
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@ -21,6 +21,18 @@ Function: "acos_upward":
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ildouble: 1
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ldouble: 1
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Function: "acosh_downward":
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ildouble: 2
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ldouble: 2
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Function: "acosh_towardzero":
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ildouble: 2
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ldouble: 2
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Function: "acosh_upward":
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ildouble: 1
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ldouble: 1
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Function: "asin_downward":
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double: 1
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float: 1
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@ -48,7 +48,7 @@ __ieee754_acoshl(long double x)
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return x+x;
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} else
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return __ieee754_logl(x)+ln2; /* acoshl(huge)=logl(2x) */
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} else if(((se-0x3fff)|i0|i1)==0) {
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} else if(((se-0x3fff)|(i0^0x80000000)|i1)==0) {
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return 0.0; /* acosh(1) = 0 */
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} else if (se > 0x4000) { /* 2**28 > x > 2 */
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t=x*x;
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@ -31,6 +31,21 @@ Function: "acosh":
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double: 1
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idouble: 1
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Function: "acosh_downward":
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float: 1
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ildouble: 1
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ldouble: 2
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Function: "acosh_towardzero":
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float: 1
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ildouble: 1
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ldouble: 2
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Function: "acosh_upward":
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double: 1
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ildouble: 1
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ldouble: 1
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Function: "asin_downward":
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double: 1
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float: 1
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