diff options
Diffstat (limited to 'sysdeps/powerpc/power7/fpu/s_logbf.c')
-rw-r--r-- | sysdeps/powerpc/power7/fpu/s_logbf.c | 60 |
1 files changed, 60 insertions, 0 deletions
diff --git a/sysdeps/powerpc/power7/fpu/s_logbf.c b/sysdeps/powerpc/power7/fpu/s_logbf.c new file mode 100644 index 0000000000..05726f2f7f --- /dev/null +++ b/sysdeps/powerpc/power7/fpu/s_logbf.c @@ -0,0 +1,60 @@ +/* logbf(). PowerPC/POWER7 version. + Copyright (C) 2012-2013 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <http://www.gnu.org/licenses/>. */ + +#include "math_private.h" + +/* This implementation avoids FP to INT conversions by using VSX + bitwise instructions over FP values. */ + +static const double two1div52 = 2.220446049250313e-16; /* 1/2**52 */ +static const double two10m1 = -1023.0; /* -2**10 + 1 */ +static const double two7m1 = -127.0; /* -2**7 + 1 */ + +/* FP mask to extract the exponent. */ +static const union { + unsigned long long mask; + double d; +} mask = { 0x7ff0000000000000ULL }; + +float +__logbf (float x) +{ + /* VSX operation are all done internally as double. */ + double ret; + + if (__builtin_expect (x == 0.0, 0)) + /* Raise FE_DIVBYZERO and return -HUGE_VAL[LF]. */ + return -1.0 / __builtin_fabsf (x); + + /* ret = x & 0x7f800000; */ + asm ( + "xxland %x0,%x1,%x2\n" + "fcfid %0,%0" + : "=f"(ret) + : "f" (x), "f" (mask.d)); + /* ret = (ret >> 52) - 1023.0, since ret is double. */ + ret = (ret * two1div52) + two10m1; + if (__builtin_expect (ret > -two7m1, 0)) + /* Multiplication is used to set logb (+-INF) = INF. */ + return (x * x); + /* Since operations are done with double we don't need + additional tests for subnormal numbers. + The test is to avoid logb_downward (0.0) == -0.0. */ + return ret == -0.0 ? 0.0 : ret; +} +weak_alias (__logbf, logbf) |