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| author | Joseph Myers <joseph@codesourcery.com> | 2015-09-15 20:48:05 +0000 |
|---|---|---|
| committer | Joseph Myers <joseph@codesourcery.com> | 2015-09-15 20:48:05 +0000 |
| commit | dfa0f62011b50cc36107df5fad4130c5368b11e1 (patch) | |
| tree | 5d1bd11790c0303dfe0d92a1c970d82ce75eee9c | |
| parent | 223d1cacc5dafe8af53e84608c2d130721c4edcd (diff) | |
| download | glibc-dfa0f62011b50cc36107df5fad4130c5368b11e1.tar.gz glibc-dfa0f62011b50cc36107df5fad4130c5368b11e1.tar.xz glibc-dfa0f62011b50cc36107df5fad4130c5368b11e1.zip | |
Fix ldbl-128ibm nearbyintl use of signaling comparisons on NaNs (bug 18857).
The ldbl-128ibm implementation of nearbyintl wrongly uses signaling comparisons such as "if (fabs (u.d[0].d) < TWO52)" on arguments that might be NaNs, when "invalid" exceptions should not be raised. (For hard float, this issue may be hidden by <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58684>, powerpc GCC wrongly only using unordered comparison instructions.) This patch fixes this by just returning the argument if it is not finite (because of the arbitrary value of the low part of a NaN in IBM long double, there are quite a lot of comparisons that could end up involving a NaN when the argument to nearbyintl is a NaN, so excluding NaN arguments at the start is the simplest and safest fix). Tested for powerpc-nofpu, where it removes failures for spurious "invalid" exceptions from nearbyintl. [BZ #18857] * sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c (__nearbyintl): Just return non-finite argument without doing ordered comparisons on it.
| -rw-r--r-- | ChangeLog | 5 | ||||
| -rw-r--r-- | NEWS | 4 | ||||
| -rw-r--r-- | sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c | 4 |
3 files changed, 10 insertions, 3 deletions
diff --git a/ChangeLog b/ChangeLog index fd281993c8..5053bf31d5 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,5 +1,10 @@ 2015-09-15 Joseph Myers <joseph@codesourcery.com> + [BZ #18857] + * sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c (__nearbyintl): Just + return non-finite argument without doing ordered comparisons on + it. + [BZ #16296] * math/fenv.h (fegetround): Use __attribute_pure__. * include/fenv.h (__fegetround): Likewise. diff --git a/NEWS b/NEWS index b35d5424d3..5db57a2e9a 100644 --- a/NEWS +++ b/NEWS @@ -13,8 +13,8 @@ Version 2.23 16519, 16520, 16521, 16734, 16973, 16985, 17787, 17905, 18084, 18086, 18240, 18265, 18370, 18421, 18480, 18525, 18595, 18610, 18618, 18647, 18661, 18674, 18675, 18681, 18757, 18778, 18781, 18787, 18789, 18790, - 18795, 18796, 18820, 18823, 18824, 18863, 18870, 18873, 18875, 18887, - 18921, 18952, 18961, 18966. + 18795, 18796, 18820, 18823, 18824, 18857, 18863, 18870, 18873, 18875, + 18887, 18921, 18952, 18961, 18966. * The obsolete header <regexp.h> has been removed. Programs that require this header must be updated to use <regex.h> instead. diff --git a/sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c b/sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c index 5f92a5fee8..99f47473b9 100644 --- a/sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c +++ b/sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c @@ -36,7 +36,9 @@ __nearbyintl (long double x) union ibm_extended_long_double u; u.ld = x; - if (fabs (u.d[0].d) < TWO52) + if (!isfinite (u.d[0].d)) + return x; + else if (fabs (u.d[0].d) < TWO52) { double xh = u.d[0].d; double high = u.d[0].d; |