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| author | Joseph Myers <joseph@codesourcery.com> | 2015-02-16 22:38:28 +0000 |
|---|---|---|
| committer | Joseph Myers <joseph@codesourcery.com> | 2015-02-16 22:38:28 +0000 |
| commit | a820f9b3c0cb5e80cd892b0f9c1c48f48bd4413f (patch) | |
| tree | e563669e7d00f3eeab3c3b8f34ddd77339c57def /sysdeps/ieee754/ldbl-96 | |
| parent | be802953a103bfd502d696f1418e2bef1b450be2 (diff) | |
| download | glibc-a820f9b3c0cb5e80cd892b0f9c1c48f48bd4413f.tar glibc-a820f9b3c0cb5e80cd892b0f9c1c48f48bd4413f.tar.gz glibc-a820f9b3c0cb5e80cd892b0f9c1c48f48bd4413f.tar.bz2 glibc-a820f9b3c0cb5e80cd892b0f9c1c48f48bd4413f.zip | |
Fix remquo spurious overflows (bug 17978).
Various remquo implementations, when computing the last three bits of
the quotient, have spurious overflows when 4 times the second argument
to remquo overflows. These overflows can in turn cause bad results in
rounding modes where that overflow results in a finite value. This
patch adds tests to avoid the problem multiplications in cases where
they would overflow, similar to those that control an earlier
multiplication by 8.
Tested for x86_64, x86, mips64 and powerpc.
[BZ #17978]
* sysdeps/ieee754/dbl-64/s_remquo.c (__remquo): Do not form
products 4 * y and 2 * y where those would overflow.
* sysdeps/ieee754/dbl-64/wordsize-64/s_remquo.c (__remquo):
Likewise.
* sysdeps/ieee754/flt-32/s_remquof.c (__remquof): Likewise.
* sysdeps/ieee754/ldbl-128/s_remquol.c (__remquol): Likewise.
* sysdeps/ieee754/ldbl-128ibm/s_remquol.c (__remquol): Likewise.
* sysdeps/ieee754/ldbl-96/s_remquol.c (__remquol): Likewise.
* math/libm-test.inc (remquo_test_data): Add more tests.
Diffstat (limited to 'sysdeps/ieee754/ldbl-96')
| -rw-r--r-- | sysdeps/ieee754/ldbl-96/s_remquol.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/sysdeps/ieee754/ldbl-96/s_remquol.c b/sysdeps/ieee754/ldbl-96/s_remquol.c index 6b3499d257..1462b54456 100644 --- a/sysdeps/ieee754/ldbl-96/s_remquol.c +++ b/sysdeps/ieee754/ldbl-96/s_remquol.c @@ -60,12 +60,12 @@ __remquol (long double x, long double p, int *quo) p = fabsl (p); cquo = 0; - if (x >= 4 * p) + if (ep <= 0x7ffc && x >= 4 * p) { x -= 4 * p; cquo += 4; } - if (x >= 2 * p) + if (ep <= 0x7ffd && x >= 2 * p) { x -= 2 * p; cquo += 2; |