From be49cd3ec6a53aa6b0b5c5635202dd92bcaacfc6 Mon Sep 17 00:00:00 2001 From: Dimitry Andric Date: Wed, 10 Feb 2021 23:28:43 +0100 Subject: [PATCH] Fix incorrect hypotl(3) result with subnormal numbers This adjusts the factor used to scale the subnormal numbers, so it becomes the right value after adjusting its exponent. Thanks to Steve Kargl for finding the most elegant fix. Also enable the hypot tests, and add a test case for this bug. PR: 253313 (cherry picked from commit d3338f3355a612cf385632291f46c5777bba8d18) Fix lib/msun/test builds on platforms without 80-bit long doubles After d3338f3355a612cf385632291f46c5777bba8d18, the lib/msun test case 'hypotl_near_underflow' would fail to compile on platforms where long doubles weren't 80 bit, like on x86. Disable this particular test on such platforms for now. PR: 253313 (cherry picked from commit 25120662284466ecef976df8f86e97bafdedf991) --- contrib/netbsd-tests/lib/libm/t_hypot.c | 24 ++++++++++++++++++++++++ lib/msun/src/e_hypotl.c | 2 +- lib/msun/tests/Makefile | 1 + 3 files changed, 26 insertions(+), 1 deletion(-) diff --git a/contrib/netbsd-tests/lib/libm/t_hypot.c b/contrib/netbsd-tests/lib/libm/t_hypot.c index deb7e86ad5a..cbb056ee470 100644 --- a/contrib/netbsd-tests/lib/libm/t_hypot.c +++ b/contrib/netbsd-tests/lib/libm/t_hypot.c @@ -70,12 +70,36 @@ ATF_TC_BODY(pr50698, tc) ATF_CHECK(!isnan(val)); } +#if __LDBL_MANT_DIG__ == 64 +ATF_TC(hypotl_near_underflow); +ATF_TC_HEAD(hypotl_near_underflow, tc) +{ + atf_tc_set_md_var(tc, "descr", "Test hypotl near underflow"); +} + +ATF_TC_BODY(hypotl_near_underflow, tc) +{ + volatile long double a = 0x1.b2933cafa0bb7p-16383L; + volatile long double b = 0x1.fffffffffffffp-16351L; + volatile long double e = 0x1.fffffffffffffp-16351L; + volatile long double ulp = __LDBL_EPSILON__; + + volatile long double val = hypotl(a, b); + + ATF_CHECK(!isinf(val)); + ATF_CHECK(fabsl(val - e) <= 2 * ulp); +} +#endif /* __LDBL_MANT_DIG__ == 64 */ + ATF_TP_ADD_TCS(tp) { ATF_TP_ADD_TC(tp, hypot_integer); ATF_TP_ADD_TC(tp, hypotf_integer); ATF_TP_ADD_TC(tp, pr50698); +#if __LDBL_MANT_DIG__ == 64 + ATF_TP_ADD_TC(tp, hypotl_near_underflow); +#endif /* __LDBL_MANT_DIG__ == 64 */ return atf_no_error(); } diff --git a/lib/msun/src/e_hypotl.c b/lib/msun/src/e_hypotl.c index 9189b1fab54..fc43538dfa6 100644 --- a/lib/msun/src/e_hypotl.c +++ b/lib/msun/src/e_hypotl.c @@ -82,7 +82,7 @@ hypotl(long double x, long double y) man_t manh, manl; GET_LDBL_MAN(manh,manl,b); if((manh|manl)==0) return a; - t1=0; + t1=1; SET_HIGH_WORD(t1,ESW(MAX_EXP-2)); /* t1=2^(MAX_EXP-2) */ b *= t1; a *= t1; diff --git a/lib/msun/tests/Makefile b/lib/msun/tests/Makefile index 949b0a5b7aa..cd60f7c71a1 100644 --- a/lib/msun/tests/Makefile +++ b/lib/msun/tests/Makefile @@ -30,6 +30,7 @@ NETBSD_ATF_TESTS_C+= erf_test NETBSD_ATF_TESTS_C+= exp_test NETBSD_ATF_TESTS_C+= fmod_test NETBSD_ATF_TESTS_C+= fe_round_test +NETBSD_ATF_TESTS_C+= hypot_test NETBSD_ATF_TESTS_C+= infinity_test NETBSD_ATF_TESTS_C+= ilogb_test NETBSD_ATF_TESTS_C+= ldexp_test -- 2.45.0