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| author | Joseph Myers <joseph@codesourcery.com> | 2015-02-12 19:02:45 +0000 |
|---|---|---|
| committer | Joseph Myers <joseph@codesourcery.com> | 2015-02-12 19:02:45 +0000 |
| commit | 03d95bd48319256bd29cfaece45919fc58bf56cc (patch) | |
| tree | 5ed21769ade47b69e555932587a23f69201c7ba6 /sysdeps | |
| parent | 98408b95b155464e760c22dce4842f29499db821 (diff) | |
| download | glibc-03d95bd48319256bd29cfaece45919fc58bf56cc.zip glibc-03d95bd48319256bd29cfaece45919fc58bf56cc.tar.gz glibc-03d95bd48319256bd29cfaece45919fc58bf56cc.tar.bz2 | |
Fix exp2 spurious underflows (bug 16560).
This patch fixes the remaining part of bug 16560, spurious underflows
from exp2 of arguments close to 0 (when the result is close to 1, so
should not underflow), by just using 1+x instead of a more complicated
calculation when the argument is sufficiently small.
Tested for x86_64, x86 and mips64.
[BZ #16560]
* math/e_exp2l.c [LDBL_MANT_DIG == 106] (LDBL_EPSILON): Undefine
and redefine.
(__ieee754_exp2l): Do not multiply small fractional parts by
M_LN2l.
* sysdeps/i386/fpu/e_exp2l.S (__ieee754_exp2l): Just add 1 to
small argument.
* sysdeps/ieee754/dbl-64/e_exp2.c (__ieee754_exp2): Likewise.
* sysdeps/ieee754/flt-32/e_exp2f.c (__ieee754_exp2f): Likewise.
* sysdeps/x86_64/fpu/e_exp2l.S (__ieee754_exp2l): Likewise.
* math/auto-libm-test-in: Add more tests of exp2.
* math/auto-libm-test-out: Regenerated.
Diffstat (limited to 'sysdeps')
| -rw-r--r-- | sysdeps/i386/fpu/e_exp2l.S | 10 | ||||
| -rw-r--r-- | sysdeps/ieee754/dbl-64/e_exp2.c | 3 | ||||
| -rw-r--r-- | sysdeps/ieee754/flt-32/e_exp2f.c | 3 | ||||
| -rw-r--r-- | sysdeps/x86_64/fpu/e_exp2l.S | 10 |
4 files changed, 24 insertions, 2 deletions
diff --git a/sysdeps/i386/fpu/e_exp2l.S b/sysdeps/i386/fpu/e_exp2l.S index 203dd00..2bf9a25 100644 --- a/sysdeps/i386/fpu/e_exp2l.S +++ b/sysdeps/i386/fpu/e_exp2l.S @@ -18,7 +18,15 @@ ENTRY(__ieee754_exp2l) andb %ah, %dh cmpb $0x05, %dh je 1f /* Is +-Inf, jump. */ - fld %st + movzwl 4+8(%esp), %eax + andl $0x7fff, %eax + cmpl $0x3fbe, %eax + jge 3f + /* Argument's exponent below -65, result rounds to 1. */ + fld1 + faddp + ret +3: fld %st frndint /* int(x) */ fsubr %st,%st(1) /* fract(x) */ fxch diff --git a/sysdeps/ieee754/dbl-64/e_exp2.c b/sysdeps/ieee754/dbl-64/e_exp2.c index 3666c6a..f964a5a 100644 --- a/sysdeps/ieee754/dbl-64/e_exp2.c +++ b/sysdeps/ieee754/dbl-64/e_exp2.c @@ -61,6 +61,9 @@ __ieee754_exp2 (double x) double rx, x22, result; union ieee754_double ex2_u, scale_u; + if (fabs (x) < DBL_EPSILON / 4.0) + return 1.0 + x; + { SET_RESTORE_ROUND_NOEX (FE_TONEAREST); diff --git a/sysdeps/ieee754/flt-32/e_exp2f.c b/sysdeps/ieee754/flt-32/e_exp2f.c index 01cd444..f3e3a8e 100644 --- a/sysdeps/ieee754/flt-32/e_exp2f.c +++ b/sysdeps/ieee754/flt-32/e_exp2f.c @@ -54,6 +54,9 @@ __ieee754_exp2f (float x) float rx, x22, result; union ieee754_float ex2_u, scale_u; + if (fabsf (x) < FLT_EPSILON / 4.0f) + return 1.0f + x; + { SET_RESTORE_ROUND_NOEXF (FE_TONEAREST); diff --git a/sysdeps/x86_64/fpu/e_exp2l.S b/sysdeps/x86_64/fpu/e_exp2l.S index 7abf425..7d42a93 100644 --- a/sysdeps/x86_64/fpu/e_exp2l.S +++ b/sysdeps/x86_64/fpu/e_exp2l.S @@ -19,7 +19,15 @@ ENTRY(__ieee754_exp2l) andb %ah, %dh cmpb $0x05, %dh je 1f /* Is +-Inf, jump. */ - fld %st + movzwl 8+8(%rsp), %eax + andl $0x7fff, %eax + cmpl $0x3fbe, %eax + jge 3f + /* Argument's exponent below -65, result rounds to 1. */ + fld1 + faddp + ret +3: fld %st frndint /* int(x) */ fsubr %st,%st(1) /* fract(x) */ fxch |