Prepare for radical source tree reorganization. zack/build-layout-experiment

All top-level files and directories are moved into a temporary storage
directory, REORG.TODO, except for files that will certainly still
exist in their current form at top level when we're done (COPYING,
COPYING.LIB, LICENSES, NEWS, README), all old ChangeLog files (which
are moved to the new directory OldChangeLogs, instead), and the
generated file INSTALL (which is just deleted; in the new order, there
will be no generated files checked into version control).

1 files changed, 132 insertions, 0 deletions

diff --git a/REORG.TODO/sysdeps/ieee754/flt-32/e_exp2f.c b/REORG.TODO/sysdeps/ieee754/flt-32/e_exp2f.c
new file mode 100644
index 0000000000..567d3ff6d0
--- /dev/null
+++ b/REORG.TODO/sysdeps/ieee754/flt-32/e_exp2f.c
@@ -0,0 +1,132 @@
+/* Single-precision floating point 2^x.
+   Copyright (C) 1997-2017 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Geoffrey Keating <geoffk@ozemail.com.au>
+
+   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/>.  */
+
+/* The basic design here is from
+   Shmuel Gal and Boris Bachelis, "An Accurate Elementary Mathematical
+   Library for the IEEE Floating Point Standard", ACM Trans. Math. Soft.,
+   17 (1), March 1991, pp. 26-45.
+   It has been slightly modified to compute 2^x instead of e^x, and for
+   single-precision.
+   */
+#ifndef _GNU_SOURCE
+# define _GNU_SOURCE
+#endif
+#include <stdlib.h>
+#include <float.h>
+#include <ieee754.h>
+#include <math.h>
+#include <fenv.h>
+#include <inttypes.h>
+#include <math_private.h>
+
+#include "t_exp2f.h"
+
+static const float TWOM100 = 7.88860905e-31;
+static const float TWO127 = 1.7014118346e+38;
+
+float
+__ieee754_exp2f (float x)
+{
+  static const float himark = (float) FLT_MAX_EXP;
+  static const float lomark = (float) (FLT_MIN_EXP - FLT_MANT_DIG - 1);
+
+  /* Check for usual case.  */
+  if (isless (x, himark) && isgreaterequal (x, lomark))
+    {
+      static const float THREEp14 = 49152.0;
+      int tval, unsafe;
+      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);
+
+	/* 1. Argument reduction.
+	   Choose integers ex, -128 <= t < 128, and some real
+	   -1/512 <= x1 <= 1/512 so that
+	   x = ex + t/512 + x1.
+
+	   First, calculate rx = ex + t/256.  */
+	rx = x + THREEp14;
+	rx -= THREEp14;
+	x -= rx;  /* Compute x=x1. */
+	/* Compute tval = (ex*256 + t)+128.
+	   Now, t = (tval mod 256)-128 and ex=tval/256  [that's mod, NOT %;
+	   and /-round-to-nearest not the usual c integer /].  */
+	tval = (int) (rx * 256.0f + 128.0f);
+
+	/* 2. Adjust for accurate table entry.
+	   Find e so that
+	   x = ex + t/256 + e + x2
+	   where -7e-4 < e < 7e-4, and
+	   (float)(2^(t/256+e))
+	   is accurate to one part in 2^-64.  */
+
+	/* 'tval & 255' is the same as 'tval%256' except that it's always
+	   positive.
+	   Compute x = x2.  */
+	x -= __exp2f_deltatable[tval & 255];
+
+	/* 3. Compute ex2 = 2^(t/255+e+ex).  */
+	ex2_u.f = __exp2f_atable[tval & 255];
+	tval >>= 8;
+	/* x2 is an integer multiple of 2^-30; avoid intermediate
+	   underflow from the calculation of x22 * x.  */
+	unsafe = abs(tval) >= -FLT_MIN_EXP - 32;
+	ex2_u.ieee.exponent += tval >> unsafe;
+	scale_u.f = 1.0;
+	scale_u.ieee.exponent += tval - (tval >> unsafe);
+
+	/* 4. Approximate 2^x2 - 1, using a second-degree polynomial,
+	   with maximum error in [-2^-9 - 2^-14, 2^-9 + 2^-14]
+	   less than 1.3e-10.  */
+
+	x22 = (.24022656679f * x + .69314736128f) * ex2_u.f;
+      }
+
+      /* 5. Return (2^x2-1) * 2^(t/512+e+ex) + 2^(t/512+e+ex).  */
+      result = x22 * x + ex2_u.f;
+
+      if (!unsafe)
+	return result;
+      else
+	{
+	  result *= scale_u.f;
+	  math_check_force_underflow_nonneg (result);
+	  return result;
+	}
+    }
+  /* Exceptional cases:  */
+  else if (isless (x, himark))
+    {
+      if (isinf (x))
+	/* e^-inf == 0, with no error.  */
+	return 0;
+      else
+	/* Underflow */
+	return TWOM100 * TWOM100;
+    }
+  else
+    /* Return x, if x is a NaN or Inf; or overflow, otherwise.  */
+    return TWO127*x;
+}
+strong_alias (__ieee754_exp2f, __exp2f_finite)