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Fix incorrect hypotl(3) result with subnormal numbers

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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 d3338f3355)

Fix lib/msun/test builds on platforms without 80-bit long doubles

After d3338f3355, 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 2512066228)
This commit is contained in:
Dimitry Andric 2021-02-10 23:28:43 +01:00
parent c558999977
commit 97232b0dc0
3 changed files with 26 additions and 1 deletions
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24
contrib/netbsd-tests/lib/libm/t_hypot.c
View file

@ -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();
}

2
lib/msun/src/e_hypotl.c
View file

@ -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;

1
lib/msun/tests/Makefile
View file

@ -31,6 +31,7 @@ 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