1 files changed, 140 insertions, 0 deletions
diff --git a/sysdeps/ieee754/flt-32/e_expf.c b/sysdeps/ieee754/flt-32/e_expf.c
new file mode 100644
index 0000000000..e8a9c9d874
--- /dev/null
+++ b/sysdeps/ieee754/flt-32/e_expf.c
@@ -0,0 +1,140 @@
+/* Single-precision floating point e^x.
+   Copyright (C) 1997, 1998 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 Library General Public License as
+   published by the Free Software Foundation; either version 2 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
+   Library General Public License for more details.
+
+   You should have received a copy of the GNU Library General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  If not,
+   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+   Boston, MA 02111-1307, USA.  */
+
+/* How this works:
+
+   The input value, x, is written as
+
+   x = n * ln(2) + t/512 + delta[t] + x;
+
+   where:
+   - n is an integer, 127 >= n >= -150;
+   - t is an integer, 177 >= t >= -177
+   - delta is based on a table entry, delta[t] < 2^-28
+   - x is whatever is left, |x| < 2^-10
+
+   Then e^x is approximated as
+
+   e^x = 2^n ( e^(t/512 + delta[t])
+               + ( e^(t/512 + delta[t])
+                   * ( p(x + delta[t] + n * ln(2)) - delta ) ) )
+
+   where
+   - p(x) is a polynomial approximating e(x)-1;
+   - e^(t/512 + delta[t]) is obtained from a table.
+
+   The table used is the same one as for the double precision version;
+   since we have the table, we might as well use it.
+
+   It turns out to be faster to do calculations in double precision than
+   to perform an 'accurate table method' expf, because of the range reduction
+   overhead (compare exp2f).
+   */
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+#include <float.h>
+#include <ieee754.h>
+#include <math.h>
+#include <fenv.h>
+#include <inttypes.h>
+#include <math_private.h>
+
+extern const float __exp_deltatable[178];
+extern const double __exp_atable[355] /* __attribute__((mode(DF))) */;
+
+static const volatile float TWOM100 = 7.88860905e-31;
+static const volatile float TWO127 = 1.7014118346e+38;
+
+float
+__ieee754_expf (float x)
+{
+  static const float himark = 88.72283935546875;
+  static const float lomark = -103.972084045410;
+  /* Check for usual case.  */
+  if (isless (x, himark) && isgreater (x, lomark))
+    {
+      static const float THREEp42 = 13194139533312.0;
+      static const float THREEp22 = 12582912.0;
+      /* 1/ln(2).  */
+#undef M_1_LN2
+      static const float M_1_LN2 = 1.44269502163f;
+      /* ln(2) */
+#undef M_LN2
+      static const double M_LN2 = .6931471805599452862;
+
+      int tval;
+      double x22, t, result, dx;
+      float n, delta;
+      union ieee754_double ex2_u;
+      fenv_t oldenv;
+
+      feholdexcept (&oldenv);
+#ifdef FE_TONEAREST
+      fesetround (FE_TONEAREST);
+#endif
+
+      /* Calculate n.  */
+      n = x * M_1_LN2 + THREEp22;
+      n -= THREEp22;
+      dx = x - n*M_LN2;
+
+      /* Calculate t/512.  */
+      t = dx + THREEp42;
+      t -= THREEp42;
+      dx -= t;
+
+      /* Compute tval = t.  */
+      tval = (int) (t * 512.0);
+
+      if (t >= 0)
+	delta = - __exp_deltatable[tval];
+      else
+	delta = __exp_deltatable[-tval];
+
+      /* Compute ex2 = 2^n e^(t/512+delta[t]).  */
+      ex2_u.d = __exp_atable[tval+177];
+      ex2_u.ieee.exponent += (int) n;
+
+      /* Approximate e^(dx+delta) - 1, using a second-degree polynomial,
+	 with maximum error in [-2^-10-2^-28,2^-10+2^-28]
+	 less than 5e-11.  */
+      x22 = (0.5000000496709180453 * dx + 1.0000001192102037084) * dx + delta;
+
+      /* Return result.  */
+      fesetenv (&oldenv);
+
+      result = x22 * ex2_u.d + ex2_u.d;
+      return (float) result;
+    }
+  /* Exceptional cases:  */
+  else if (isless (x, himark))
+    {
+      if (__isinff (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;
+}