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author | Joseph Myers <joseph@codesourcery.com> | 2015-01-12 23:02:14 +0000 |
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committer | Joseph Myers <joseph@codesourcery.com> | 2015-01-12 23:02:14 +0000 |
commit | 5a9e4c09a2601a8100ea9a1f7bc0360782cd1625 (patch) | |
tree | f70efee88fe34c9f405165c4241978724ccf3282 /math/test-misc.c | |
parent | 34e93d6c76b7a6eaf94697a172b958704fd33396 (diff) | |
download | glibc-5a9e4c09a2601a8100ea9a1f7bc0360782cd1625.tar.gz glibc-5a9e4c09a2601a8100ea9a1f7bc0360782cd1625.tar.xz glibc-5a9e4c09a2601a8100ea9a1f7bc0360782cd1625.zip |
Fix ldbl-96 scalblnl underflowing results (bug 17803).
The ldbl-96 implementation of scalblnl (used for x86_64 and ia64) uses a condition k <= -63 to determine when a standard underflowing result tiny*__copysignl(tiny,x) should be returned. However, that condition corresponds to values with exponent -16446 or less, and in the case of -16446, the correct result for round-to-nearest depends on whether the value is exactly 0x1p-16446 (half the least subnormal) or more than that. This patch fixes the bug by changing the condition to k <= -64 and accordingly adjusting the exponent by 64 not 63 when converting to a normal value. Tested for x86_64. [BZ #17803] * sysdeps/ieee754/ldbl-96/s_scalblnl.c (twom63): Rename to twom64. Adjust value to 0x1p-64L. (__scalblnl): Only return standard underflowing result for K <= -64 not K <= -63; adjust exponent for underflowing result by 64 not 63. * math/libm-test.inc (scalbn_test_data): Add more tests. (scalbln_test_data): Likewise.
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