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| author | Joseph Myers <joseph@codesourcery.com> | 2014-03-21 18:13:58 +0000 |
|---|---|---|
| committer | Joseph Myers <joseph@codesourcery.com> | 2014-03-21 18:13:58 +0000 |
| commit | f7be737659813220e1f29c8850c386a9654d549a (patch) | |
| tree | c047f314e8eca5df155322e4fe9471593fb07b67 /sysdeps/i386/fpu/e_log.S | |
| parent | a387428ca7330513d5f2a0924c45e6382d477052 (diff) | |
| download | glibc-f7be737659813220e1f29c8850c386a9654d549a.tar.gz glibc-f7be737659813220e1f29c8850c386a9654d549a.tar.xz glibc-f7be737659813220e1f29c8850c386a9654d549a.zip | |
Fix log (1) in round-downward mode (bug 16731).
According to ISO C Annex F, log (1) should be +0 in all rounding modes, but some implementations in glibc wrongly return -0 in round-downward mode (mapping to log1p (x - 1) is problematic because 1 - 1 is -0 in round-downward mode, and log1p (-0) is -0). This patch fixes this. (It helps with some implementations of other functions such as acosh, log2 and log10 that call out to log, but not enough to enable all-rounding-modes testing for those functions without further fixes to other implementations of them.) Tested x86_64 and x86 and ulps updated accordingly, and did spot tests for mips64 for the ldbl-128 fix, and i586 for the sysdeps/i386/fpu implementations shadowed by those in sysdeps/i386/i686/fpu. [BZ #16731] * sysdeps/i386/fpu/e_log.S (__ieee754_log): Take absolute value when x - 1 is zero. * sysdeps/i386/fpu/e_logf.S (__ieee754_logf): Likewise. * sysdeps/i386/fpu/e_logl.S (__ieee754_logl): Likewise. * sysdeps/i386/i686/fpu/e_logl.S (__ieee754_logl): Likewise. * sysdeps/ieee754/dbl-64/e_log.c (__ieee754_log): Return +0 when argument is 1. * sysdeps/ieee754/ldbl-128/e_logl.c (__ieee754_logl): Likewise. * sysdeps/x86_64/fpu/e_logl.S: Take absolute value when x - 1 is zero. * math/libm-test.inc (log_test): Use ALL_RM_TEST. * sysdeps/i386/fpu/libm-test-ulps: Update. * sysdeps/x86_64/fpu/libm-test-ulps: Likewise.
Diffstat (limited to 'sysdeps/i386/fpu/e_log.S')
| -rw-r--r-- | sysdeps/i386/fpu/e_log.S | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/sysdeps/i386/fpu/e_log.S b/sysdeps/i386/fpu/e_log.S index 0877924998..3fa32aad3c 100644 --- a/sysdeps/i386/fpu/e_log.S +++ b/sysdeps/i386/fpu/e_log.S @@ -46,7 +46,13 @@ ENTRY(__ieee754_log) fnstsw // x-1 : x : log(2) andb $0x45, %ah jz 2f - fstp %st(1) // x-1 : log(2) + fxam + fnstsw + andb $0x45, %ah + cmpb $0x40, %ah + jne 5f + fabs // log(1) is +0 in all rounding modes. +5: fstp %st(1) // x-1 : log(2) fyl2xp1 // log(x) ret |