From: Joseph Myers Date: Wed, 14 May 2014 12:35:40 +0000 (+0000) Subject: Fix acosh (1) in round-downward mode (bug 16927). X-Git-Tag: glibc-2.20~514 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=913d03c864ea2547e97f8d2d30fc71a008d4d103;p=thirdparty%2Fglibc.git 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. --- diff --git a/ChangeLog b/ChangeLog index 62192f3b935..a4376290adf 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,5 +1,17 @@ 2014-05-14 Joseph Myers + [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. + [BZ #16516] * sysdeps/ieee754/dbl-64/s_erf.c (efx8): Remove variable. (__erf): Scale by 16 instead of 8 in potentially underflowing diff --git a/NEWS b/NEWS index 9293f802f8f..974d2c80a93 100644 --- a/NEWS +++ b/NEWS @@ -17,7 +17,7 @@ Version 2.20 16713, 16714, 16731, 16739, 16740, 16743, 16754, 16758, 16759, 16760, 16770, 16786, 16789, 16791, 16799, 16800, 16815, 16823, 16824, 16831, 16838, 16854, 16876, 16877, 16885, 16888, 16890, 16912, 16916, 16922, - 16932. + 16927, 16932. * The minimum Linux kernel version that this version of the GNU C Library can be used with is 2.6.32. diff --git a/math/libm-test.inc b/math/libm-test.inc index a4bf0b88c3c..b4177e8f8e0 100644 --- a/math/libm-test.inc +++ b/math/libm-test.inc @@ -1792,9 +1792,7 @@ static const struct test_f_f_data acosh_test_data[] = static void acosh_test (void) { - START (acosh, 0); - RUN_TEST_LOOP_f_f (acosh, acosh_test_data, ); - END; + ALL_RM_TEST (acosh, 0, acosh_test_data, RUN_TEST_LOOP_f_f, END); } static const struct test_f_f_data asin_test_data[] = diff --git a/sysdeps/i386/fpu/e_acosh.S b/sysdeps/i386/fpu/e_acosh.S index 98a329179bf..c66781c9859 100644 --- a/sysdeps/i386/fpu/e_acosh.S +++ b/sysdeps/i386/fpu/e_acosh.S @@ -52,6 +52,7 @@ ENTRY(__ieee754_acosh) // 1 <= x <= 2 => y = log1p(x-1+sqrt(2*(x-1)+(x-1)^2)) fsubl MO(one) // x-1 : log(2) + fabs // acosh(1) is +0 in all rounding modes fld %st // x-1 : x-1 : log(2) fmul %st(1) // (x-1)^2 : x-1 : log(2) fadd %st(1) // x-1+(x-1)^2 : x-1 : log(2) diff --git a/sysdeps/i386/fpu/e_acoshf.S b/sysdeps/i386/fpu/e_acoshf.S index db9cf337b26..fa35d50fd07 100644 --- a/sysdeps/i386/fpu/e_acoshf.S +++ b/sysdeps/i386/fpu/e_acoshf.S @@ -52,6 +52,7 @@ ENTRY(__ieee754_acoshf) // 1 <= x <= 2 => y = log1p(x-1+sqrt(2*(x-1)+(x-1)^2)) fsubl MO(one) // x-1 : log(2) + fabs // acosh(1) is +0 in all rounding modes fld %st // x-1 : x-1 : log(2) fmul %st(1) // (x-1)^2 : x-1 : log(2) fadd %st(1) // x-1+(x-1)^2 : x-1 : log(2) diff --git a/sysdeps/i386/fpu/e_acoshl.S b/sysdeps/i386/fpu/e_acoshl.S index a832155d17d..38d8110550b 100644 --- a/sysdeps/i386/fpu/e_acoshl.S +++ b/sysdeps/i386/fpu/e_acoshl.S @@ -59,6 +59,7 @@ ENTRY(__ieee754_acoshl) // 1 <= x <= 2 => y = log1p(x-1+sqrt(2*(x-1)+(x-1)^2)) fsubl MO(one) // x-1 : log(2) + fabs // acosh(1) is +0 in all rounding modes fld %st // x-1 : x-1 : log(2) fmul %st(1) // (x-1)^2 : x-1 : log(2) fadd %st(1) // x-1+(x-1)^2 : x-1 : log(2) diff --git a/sysdeps/i386/fpu/libm-test-ulps b/sysdeps/i386/fpu/libm-test-ulps index aea6c51b233..ccef44ac638 100644 --- a/sysdeps/i386/fpu/libm-test-ulps +++ b/sysdeps/i386/fpu/libm-test-ulps @@ -21,6 +21,18 @@ Function: "acos_upward": ildouble: 1 ldouble: 1 +Function: "acosh_downward": +ildouble: 2 +ldouble: 2 + +Function: "acosh_towardzero": +ildouble: 2 +ldouble: 2 + +Function: "acosh_upward": +ildouble: 1 +ldouble: 1 + Function: "asin_downward": double: 1 float: 1 diff --git a/sysdeps/ieee754/ldbl-96/e_acoshl.c b/sysdeps/ieee754/ldbl-96/e_acoshl.c index bbaef680bd5..cf9a6db0ef3 100644 --- a/sysdeps/ieee754/ldbl-96/e_acoshl.c +++ b/sysdeps/ieee754/ldbl-96/e_acoshl.c @@ -48,7 +48,7 @@ __ieee754_acoshl(long double x) return x+x; } else return __ieee754_logl(x)+ln2; /* acoshl(huge)=logl(2x) */ - } else if(((se-0x3fff)|i0|i1)==0) { + } else if(((se-0x3fff)|(i0^0x80000000)|i1)==0) { return 0.0; /* acosh(1) = 0 */ } else if (se > 0x4000) { /* 2**28 > x > 2 */ t=x*x; diff --git a/sysdeps/x86_64/fpu/libm-test-ulps b/sysdeps/x86_64/fpu/libm-test-ulps index 4ba83a46fd4..ad8ae9ce5c6 100644 --- a/sysdeps/x86_64/fpu/libm-test-ulps +++ b/sysdeps/x86_64/fpu/libm-test-ulps @@ -31,6 +31,21 @@ Function: "acosh": double: 1 idouble: 1 +Function: "acosh_downward": +float: 1 +ildouble: 1 +ldouble: 2 + +Function: "acosh_towardzero": +float: 1 +ildouble: 1 +ldouble: 2 + +Function: "acosh_upward": +double: 1 +ildouble: 1 +ldouble: 1 + Function: "asin_downward": double: 1 float: 1