From a638de828d877376fb238efc8b0bc9220dd2601e Mon Sep 17 00:00:00 2001 From: Joseph Myers Date: Wed, 25 Jun 2014 11:33:22 +0000 Subject: Fix exp10 spurious underflows (bug 16560). This patch fixes spurious underflows from exp10 for arguments near 0 (part of bug 16560; that bug also includes spurious underflows from exp2, which are not fixed by this patch). The problem is underflows in the internal computation converting the exp10 argument to arguments for exp (with extra precision), and the fix is simply to return 1 early for arguments near enough to 0 (just as arguments with large enough magnitude have their own overflow / underflow logic at the start of the function). Tested x86_64 and x86 and ulps updated accordingly; also tested for powerpc32 and mips64 to validate the ldbl-128ibm and ldbl-128 changes. [BZ #16560] * sysdeps/ieee754/dbl-64/e_exp10.c (__ieee754_exp10): Return 1 for arguments close to 0. * sysdeps/ieee754/ldbl-128/e_exp10l.c (__ieee754_exp10l): Likewise. * sysdeps/ieee754/ldbl-128ibm/e_exp10l.c (__ieee754_exp10l): Likewise. * math/auto-libm-test-in: Add more tests of exp10. * math/auto-libm-test-out: Regenerated. * sysdeps/x86_64/fpu/libm-test-ulps: Update. --- sysdeps/ieee754/ldbl-128ibm/e_exp10l.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'sysdeps/ieee754/ldbl-128ibm/e_exp10l.c') diff --git a/sysdeps/ieee754/ldbl-128ibm/e_exp10l.c b/sysdeps/ieee754/ldbl-128ibm/e_exp10l.c index 5c68eb5..a0e8a3e 100644 --- a/sysdeps/ieee754/ldbl-128ibm/e_exp10l.c +++ b/sysdeps/ieee754/ldbl-128ibm/e_exp10l.c @@ -35,6 +35,8 @@ __ieee754_exp10l (long double arg) return LDBL_MIN * LDBL_MIN; else if (arg > LDBL_MAX_10_EXP + 1) return LDBL_MAX * LDBL_MAX; + else if (fabsl (arg) < 0x1p-109L) + return 1.0L; u.ld = arg; arg_high = u.d[0].d; -- cgit v1.1