Add new log implementation

Optimized log using carefully generated lookup table with 1/c and log(c)
values for small intervalls around 1.  The log(c) is very near a double
precision value, it has about 62 bits precision.  The algorithm is
log(2^k x) = k log(2) + log(c) + log(x/c), where the last term is
approximated by a polynomial of x/c - 1.  Near 1 a single polynomial of
x - 1 is used.

There is separate code path when fma instruction is not available for
computing x/c - 1 precisely, in which case the table size is doubled.
The code uses __builtin_fma under __FP_FAST_FMA to ensure it is inlined
as an instruction.

With the default configuration settings the worst case error is 0.519 ULP
(and 0.520 without fma), the rodata size is 2192 bytes (4240 without fma).
The non-nearest rounding error is less than 1 ULP.

Improvements on Cortex-A72 compared to current glibc master:
log thruput: 3.28x in [0.01 11.1]
log latency: 2.23x in [0.01 11.1]
log thruput: 1.56x in [0.999 1.001]
log latency: 1.57x in [0.999 1.001]

Tested on
aarch64-linux-gnu (defined __FP_FAST_FMA)
arm-linux-gnueabihf (!defined __FP_FAST_FMA)
x86_64-linux-gnu (!defined __FP_FAST_FMA)
powerpc64le-linux-gnu (defined __FP_FAST_FMA)
targets.

	* NEWS: Mention log improvement.
	* math/Makefile (type-double-routines): Add e_log_data.
	* sysdeps/i386/fpu/e_log_data.c: New file.
	* sysdeps/ia64/fpu/e_log_data.c: New file.
	* sysdeps/ieee754/dbl-64/e_log.c: Rewrite.
	* sysdeps/ieee754/dbl-64/e_log_data.c: New file.
	* sysdeps/ieee754/dbl-64/math_config.h (__log_data): Add.
	* sysdeps/ieee754/dbl-64/ulog.h: Remove.
	* sysdeps/ieee754/dbl-64/ulog.tbl: Remove.
	* sysdeps/m68k/m680x0/fpu/e_log_data.c: New file.

1 files changed, 0 insertions, 93 deletions

diff --git a/sysdeps/ieee754/dbl-64/ulog.h b/sysdeps/ieee754/dbl-64/ulog.h
deleted file mode 100644
index 087b76e2ab..0000000000
--- a/sysdeps/ieee754/dbl-64/ulog.h
+++ /dev/null
@@ -1,93 +0,0 @@
-/*
- * IBM Accurate Mathematical Library
- * Written by International Business Machines Corp.
- * Copyright (C) 2001-2018 Free Software Foundation, Inc.
- *
- * This program 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.
- *
- * This program 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 this program; if not, see <http://www.gnu.org/licenses/>.
- */
-
-/******************************************************************/
-/*                                                                */
-/* MODULE_NAME:ulog.h                                             */
-/*                                                                */
-/* common data and variables prototype and definition             */
-/******************************************************************/
-
-#ifndef ULOG_H
-#define ULOG_H
-
-#ifdef BIG_ENDI
-  static const number
-  /* polynomial I */
-/**/ a2             = {{0xbfe00000, 0x0001aa8f} }, /* -0.500... */
-/**/ a3             = {{0x3fd55555, 0x55588d2e} }, /*  0.333... */
-  /* polynomial II */
-/**/ b0             = {{0x3fd55555, 0x55555555} }, /*  0.333... */
-/**/ b1             = {{0xbfcfffff, 0xffffffbb} }, /* -0.249... */
-/**/ b2             = {{0x3fc99999, 0x9999992f} }, /*  0.199... */
-/**/ b3             = {{0xbfc55555, 0x556503fd} }, /* -0.166... */
-/**/ b4             = {{0x3fc24924, 0x925b3d62} }, /*  0.142... */
-/**/ b5             = {{0xbfbffffe, 0x160472fc} }, /* -0.124... */
-/**/ b6             = {{0x3fbc71c5, 0x25db58ac} }, /*  0.111... */
-/**/ b7             = {{0xbfb9a4ac, 0x11a2a61c} }, /* -0.100... */
-/**/ b8             = {{0x3fb75077, 0x0df2b591} }, /*  0.091... */
-  /* constants    */
-/**/ sqrt_2         = {{0x3ff6a09e, 0x667f3bcc} }, /* sqrt(2)   */
-/**/ h1             = {{0x3fd2e000, 0x00000000} }, /* 151/2**9  */
-/**/ h2             = {{0x3f669000, 0x00000000} }, /* 361/2**17 */
-/**/ delu           = {{0x3f700000, 0x00000000} }, /* 1/2**8    */
-/**/ delv           = {{0x3ef00000, 0x00000000} }, /* 1/2**16   */
-/**/ ln2a           = {{0x3fe62e42, 0xfefa3800} }, /* ln(2) 43 bits */
-/**/ ln2b           = {{0x3d2ef357, 0x93c76730} }, /* ln(2)-ln2a    */
-/**/ two54          = {{0x43500000, 0x00000000} }, /* 2**54         */
-/**/ u03            = {{0x3f9eb851, 0xeb851eb8} }; /* 0.03          */
-
-#else
-#ifdef LITTLE_ENDI
-  static const number
-  /* polynomial I */
-/**/ a2             = {{0x0001aa8f, 0xbfe00000} }, /* -0.500... */
-/**/ a3             = {{0x55588d2e, 0x3fd55555} }, /*  0.333... */
-  /* polynomial II */
-/**/ b0             = {{0x55555555, 0x3fd55555} }, /*  0.333... */
-/**/ b1             = {{0xffffffbb, 0xbfcfffff} }, /* -0.249... */
-/**/ b2             = {{0x9999992f, 0x3fc99999} }, /*  0.199... */
-/**/ b3             = {{0x556503fd, 0xbfc55555} }, /* -0.166... */
-/**/ b4             = {{0x925b3d62, 0x3fc24924} }, /*  0.142... */
-/**/ b5             = {{0x160472fc, 0xbfbffffe} }, /* -0.124... */
-/**/ b6             = {{0x25db58ac, 0x3fbc71c5} }, /*  0.111... */
-/**/ b7             = {{0x11a2a61c, 0xbfb9a4ac} }, /* -0.100... */
-/**/ b8             = {{0x0df2b591, 0x3fb75077} }, /*  0.091... */
-  /* constants    */
-/**/ sqrt_2         = {{0x667f3bcc, 0x3ff6a09e} }, /* sqrt(2)   */
-/**/ h1             = {{0x00000000, 0x3fd2e000} }, /* 151/2**9  */
-/**/ h2             = {{0x00000000, 0x3f669000} }, /* 361/2**17 */
-/**/ delu           = {{0x00000000, 0x3f700000} }, /* 1/2**8    */
-/**/ delv           = {{0x00000000, 0x3ef00000} }, /* 1/2**16   */
-/**/ ln2a           = {{0xfefa3800, 0x3fe62e42} }, /* ln(2) 43 bits */
-/**/ ln2b           = {{0x93c76730, 0x3d2ef357} }, /* ln(2)-ln2a    */
-/**/ two54          = {{0x00000000, 0x43500000} }, /* 2**54         */
-/**/ u03            = {{0xeb851eb8, 0x3f9eb851} }; /* 0.03          */
-
-#endif
-#endif
-
-#define  SQRT_2    sqrt_2.d
-#define  DEL_U     delu.d
-#define  DEL_V     delv.d
-#define  LN2A      ln2a.d
-#define  LN2B      ln2b.d
-#define  U03       u03.d
-
-#endif