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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/dbl-64/s_remquo.c | |
parent | be802953a103bfd502d696f1418e2bef1b450be2 (diff) | |
download | glibc-a820f9b3c0cb5e80cd892b0f9c1c48f48bd4413f.tar.gz |
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/dbl-64/s_remquo.c')
-rw-r--r-- | sysdeps/ieee754/dbl-64/s_remquo.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/sysdeps/ieee754/dbl-64/s_remquo.c b/sysdeps/ieee754/dbl-64/s_remquo.c index 2724902908..e07efa89f8 100644 --- a/sysdeps/ieee754/dbl-64/s_remquo.c +++ b/sysdeps/ieee754/dbl-64/s_remquo.c @@ -60,12 +60,12 @@ __remquo (double x, double y, int *quo) y = fabs (y); cquo = 0; - if (x >= 4 * y) + if (hy <= 0x7fcfffff && x >= 4 * y) { x -= 4 * y; cquo += 4; } - if (x >= 2 * y) + if (hy <= 0x7fdfffff && x >= 2 * y) { x -= 2 * y; cquo += 2; |