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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 /manual | |
| parent | be802953a103bfd502d696f1418e2bef1b450be2 (diff) | |
| download | glibc-a820f9b3c0cb5e80cd892b0f9c1c48f48bd4413f.tar.gz glibc-a820f9b3c0cb5e80cd892b0f9c1c48f48bd4413f.tar.xz 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 'manual')
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