| /* logbl(). PowerPC/POWER7 version. |
| Copyright (C) 2012-2014 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.h> |
| #include <math_private.h> |
| #include <math_ldbl_opt.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 */ |
| |
| /* FP mask to extract the exponent. */ |
| static const union { |
| unsigned long long mask; |
| double d; |
| } mask = { 0x7ff0000000000000ULL }; |
| |
| long double |
| __logbl (long double x) |
| { |
| double xh; |
| double ret; |
| |
| if (__builtin_expect (x == 0.0L, 0)) |
| /* Raise FE_DIVBYZERO and return -HUGE_VAL[LF]. */ |
| return -1.0L / __builtin_fabsl (x); |
| |
| xh = ldbl_high (x); |
| /* ret = x & 0x7ff0000000000000; */ |
| asm ( |
| "xxland %x0,%x1,%x2\n" |
| "fcfid %0,%0" |
| : "=f" (ret) |
| : "f" (xh), "f" (mask.d)); |
| /* ret = (ret >> 52) - 1023.0; */ |
| ret = (ret * two1div52) + two10m1; |
| if (__builtin_expect (ret > -two10m1, 0)) |
| /* Multiplication is used to set logb (+-INF) = INF. */ |
| return (xh * xh); |
| else if (__builtin_expect (ret == two10m1, 0)) |
| { |
| /* POSIX specifies that denormal number is treated as |
| though it were normalized. */ |
| int64_t hx; |
| |
| EXTRACT_WORDS64 (hx, xh); |
| return (long double) (-1023 - (__builtin_clzll (hx) - 12)); |
| } |
| /* Test to avoid logb_downward (0.0) == -0.0. */ |
| return ret == -0.0 ? 0.0 : ret; |
| } |
| #ifndef __logbl |
| long_double_symbol (libm, __logbl, logbl); |
| #endif |
