Remove slow paths from pow

Remove the slow paths from pow.  Like several other double precision math
functions, pow is exactly rounded.  This is not required from math functions
and causes major overheads as it requires multiple fallbacks using higher
precision arithmetic if a result is close to 0.5ULP.  Ridiculous slowdowns
of up to 100000x have been reported when the highest precision path triggers.

All GLIBC math tests pass on AArch64 and x64 (with ULP of pow set to 1).
The worst case error is ~0.506ULP.  A simple test over a few hundred million
values shows pow is 10% faster on average.  This fixes BZ #13932.

	[BZ #13932]
	* sysdeps/ieee754/dbl-64/uexp.h (err_1): Remove.
	* benchtests/pow-inputs: Update comment for slow path cases.
	* manual/probes.texi (slowpow_p10): Delete removed probe.
	(slowpow_p10): Likewise.
	* math/Makefile: Remove halfulp.c and slowpow.c.
	* sysdeps/aarch64/libm-test-ulps: Set ULP of pow to 1.
	* sysdeps/generic/math_private.h (__exp1): Remove error argument.
	(__halfulp): Remove.
	(__slowpow): Remove.
	* sysdeps/i386/fpu/halfulp.c: Delete file.
	* sysdeps/i386/fpu/slowpow.c: Likewise.
	* sysdeps/ia64/fpu/halfulp.c: Likewise.
	* sysdeps/ia64/fpu/slowpow.c: Likewise.
	* sysdeps/ieee754/dbl-64/e_exp.c (__exp1): Remove error argument,
	improve comments and add error analysis.
	* sysdeps/ieee754/dbl-64/e_pow.c (__ieee754_pow): Add error analysis.
	(power1): Remove function:
	(log1): Remove error argument, add error analysis.
	(my_log2): Remove function.
	* sysdeps/ieee754/dbl-64/halfulp.c: Delete file.
	* sysdeps/ieee754/dbl-64/slowpow.c: Likewise.
	* sysdeps/m68k/m680x0/fpu/halfulp.c: Likewise.
	* sysdeps/m68k/m680x0/fpu/slowpow.c: Likewise.
	* sysdeps/powerpc/power4/fpu/Makefile: Remove CPPFLAGS-slowpow.c.
	* sysdeps/x86_64/fpu/libm-test-ulps: Set ULP of pow to 1.
	* sysdeps/x86_64/fpu/multiarch/Makefile: Remove slowpow-fma.c,
	slowpow-fma4.c, halfulp-fma.c, halfulp-fma4.c.
	* sysdeps/x86_64/fpu/multiarch/e_pow-fma.c (__slowpow): Remove define.
	* sysdeps/x86_64/fpu/multiarch/e_pow-fma4.c (__slowpow): Likewise.
	* sysdeps/x86_64/fpu/multiarch/halfulp-fma.c: Delete file.
	* sysdeps/x86_64/fpu/multiarch/halfulp-fma4.c: Likewise.
	* sysdeps/x86_64/fpu/multiarch/slowpow-fma.c: Likewise.
	* sysdeps/x86_64/fpu/multiarch/slowpow-fma4.c: Likewise.

5 files changed, 40 insertions, 453 deletions

diff --git a/sysdeps/ieee754/dbl-64/e_exp.c b/sysdeps/ieee754/dbl-64/e_exp.c
index 3d2560c9c0..7a9daa5858 100644
--- a/sysdeps/ieee754/dbl-64/e_exp.c
+++ b/sysdeps/ieee754/dbl-64/e_exp.c
@@ -233,13 +233,10 @@ ret:
 strong_alias (__ieee754_exp, __exp_finite)
 #endif
 
-/* Compute e^(x+xx).  The routine also receives bound of error of previous
-   calculation.  If after computing exp the error exceeds the allowed bounds,
-   the routine returns a non-positive number.  Otherwise it returns the
-   computed result, which is always positive.  */
+/* Compute e^(x+xx).  */
 double
 SECTION
-__exp1 (double x, double xx, double error)
+__exp1 (double x, double xx)
 {
   double bexp, t, eps, del, base, y, al, bet, res, rem, cor;
   mynumber junk1, junk2, binexp = {{0, 0}};
@@ -249,6 +246,7 @@ __exp1 (double x, double xx, double error)
   m = junk1.i[HIGH_HALF];
   n = m & hugeint;		/* no sign */
 
+  /* fabs (x) > 5.551112e-17 and fabs (x) < 7.080010e+02.  */
   if (n > smallint && n < bigint)
     {
       y = x * log2e.x + three51.x;
@@ -276,11 +274,9 @@ __exp1 (double x, double xx, double error)
 
       rem = (bet + bet * eps) + al * eps;
       res = al + rem;
-      cor = (al - res) + rem;
-      if (res == (res + cor * (1.0 + error + err_1)))
-	return res * binexp.x;
-      else
-	return -10.0;
+      /* Maximum relative error before rounding is 8.8e-22 (69.9 bits).
+	 Maximum ULP error is 0.500008.  */
+      return res * binexp.x;
     }
 
   if (n <= smallint)
@@ -318,6 +314,7 @@ __exp1 (double x, double xx, double error)
   cor = (al - res) + rem;
   if (m >> 31)
     {
+      /* x < 0.  */
       ex = junk1.i[LOW_HALF];
       if (res < 1.0)
 	{
@@ -328,34 +325,25 @@ __exp1 (double x, double xx, double error)
       if (ex >= -1022)
 	{
 	  binexp.i[HIGH_HALF] = (1023 + ex) << 20;
-	  if (res == (res + cor * (1.0 + error + err_1)))
-	    return res * binexp.x;
-	  else
-	    return -10.0;
+	  /* Maximum ULP error is 0.500008.  */
+	  return res * binexp.x;
 	}
+      /* Denormal case - ex < -1022.  */
       ex = -(1022 + ex);
       binexp.i[HIGH_HALF] = (1023 - ex) << 20;
       res *= binexp.x;
       cor *= binexp.x;
-      eps = 1.00000000001 + (error + err_1) * binexp.x;
       t = 1.0 + res;
       y = ((1.0 - t) + res) + cor;
       res = t + y;
-      cor = (t - res) + y;
-      if (res == (res + eps * cor))
-	{
-	  binexp.i[HIGH_HALF] = 0x00100000;
-	  return (res - 1.0) * binexp.x;
-	}
-      else
-	return -10.0;
+      binexp.i[HIGH_HALF] = 0x00100000;
+      /* Maximum ULP error is 0.500004.  */
+      return (res - 1.0) * binexp.x;
     }
   else
     {
       binexp.i[HIGH_HALF] = (junk1.i[LOW_HALF] + 767) << 20;
-      if (res == (res + cor * (1.0 + error + err_1)))
-	return res * binexp.x * t256.x;
-      else
-	return -10.0;
+      /* Maximum ULP error is 0.500008.  */
+      return res * binexp.x * t256.x;
     }
 }
diff --git a/sysdeps/ieee754/dbl-64/e_pow.c b/sysdeps/ieee754/dbl-64/e_pow.c
index f6e5fcdbce..542d03a7e3 100644
--- a/sysdeps/ieee754/dbl-64/e_pow.c
+++ b/sysdeps/ieee754/dbl-64/e_pow.c
@@ -20,13 +20,9 @@
 /*  MODULE_NAME: upow.c                                                    */
 /*                                                                         */
 /*  FUNCTIONS: upow                                                        */
-/*             power1                                                      */
-/*             my_log2                                                     */
 /*             log1                                                        */
 /*             checkint                                                    */
 /* FILES NEEDED: dla.h endian.h mpa.h mydefs.h                             */
-/*               halfulp.c mpexp.c mplog.c slowexp.c slowpow.c mpa.c       */
-/*                          uexp.c  upow.c				   */
 /*               root.tbl uexp.tbl upow.tbl                                */
 /* An ultimate power routine. Given two IEEE double machine numbers y,x    */
 /* it computes the correctly rounded (to nearest) value of x^y.            */
@@ -50,11 +46,8 @@
 
 static const double huge = 1.0e300, tiny = 1.0e-300;
 
-double __exp1 (double x, double xx, double error);
-static double log1 (double x, double *delta, double *error);
-static double my_log2 (double x, double *delta, double *error);
-double __slowpow (double x, double y, double z);
-static double power1 (double x, double y);
+double __exp1 (double x, double xx);
+static double log1 (double x, double *delta);
 static int checkint (double x);
 
 /* An ultimate power routine. Given two IEEE double machine numbers y, x it
@@ -63,7 +56,7 @@ double
 SECTION
 __ieee754_pow (double x, double y)
 {
-  double z, a, aa, error, t, a1, a2, y1, y2;
+  double z, a, aa, t, a1, a2, y1, y2;
   mynumber u, v;
   int k;
   int4 qx, qy;
@@ -100,7 +93,7 @@ __ieee754_pow (double x, double y)
 	   not matter if |y| <= 2**-64.  */
 	if (fabs (y) < 0x1p-64)
 	  y = y < 0 ? -0x1p-64 : 0x1p-64;
-	z = log1 (x, &aa, &error);	/* x^y  =e^(y log (X)) */
+	z = log1 (x, &aa);	/* x^y  =e^(y log (X)) */
 	t = y * CN;
 	y1 = t - (t - y);
 	y2 = y - y1;
@@ -111,9 +104,16 @@ __ieee754_pow (double x, double y)
 	aa = y2 * a1 + y * a2;
 	a1 = a + aa;
 	a2 = (a - a1) + aa;
-	error = error * fabs (y);
-	t = __exp1 (a1, a2, 1.9e16 * error);	/* return -10 or 0 if wasn't computed exactly */
-	retval = (t > 0) ? t : power1 (x, y);
+
+	/* Maximum relative error RElog of log1 is 1.0e-21 (69.7 bits).
+	   Maximum relative error REexp of __exp1 is 8.8e-22 (69.9 bits).
+	   We actually compute exp ((1 + RElog) * log (x) * y) * (1 + REexp).
+	   Since RElog/REexp are tiny and log (x) * y is at most log (DBL_MAX),
+	   this is equivalent to pow (x, y) * (1 + 710 * RElog + REexp).
+	   So the relative error is 710 * 1.0e-21 + 8.8e-22 = 7.1e-19
+	   (60.2 bits).  The worst-case ULP error is 0.5064.  */
+
+	retval = __exp1 (a1, a2);
       }
 
       if (isinf (retval))
@@ -218,33 +218,11 @@ __ieee754_pow (double x, double y)
 strong_alias (__ieee754_pow, __pow_finite)
 #endif
 
-/* Compute x^y using more accurate but more slow log routine.  */
-static double
-SECTION
-power1 (double x, double y)
-{
-  double z, a, aa, error, t, a1, a2, y1, y2;
-  z = my_log2 (x, &aa, &error);
-  t = y * CN;
-  y1 = t - (t - y);
-  y2 = y - y1;
-  t = z * CN;
-  a1 = t - (t - z);
-  a2 = z - a1;
-  a = y * z;
-  aa = ((y1 * a1 - a) + y1 * a2 + y2 * a1) + y2 * a2 + aa * y;
-  a1 = a + aa;
-  a2 = (a - a1) + aa;
-  error = error * fabs (y);
-  t = __exp1 (a1, a2, 1.9e16 * error);
-  return (t >= 0) ? t : __slowpow (x, y, z);
-}
-
 /* Compute log(x) (x is left argument). The result is the returned double + the
-   parameter DELTA.  The result is bounded by ERROR.  */
+   parameter DELTA.  */
 static double
 SECTION
-log1 (double x, double *delta, double *error)
+log1 (double x, double *delta)
 {
   unsigned int i, j;
   int m;
@@ -260,9 +238,7 @@ log1 (double x, double *delta, double *error)
 
   u.x = x;
   m = u.i[HIGH_HALF];
-  *error = 0;
-  *delta = 0;
-  if (m < 0x00100000)		/*  1<x<2^-1007 */
+  if (m < 0x00100000)		/* Handle denormal x.  */
     {
       x = x * t52.x;
       add = -52.0;
@@ -284,7 +260,7 @@ log1 (double x, double *delta, double *error)
   v.x = u.x + bigu.x;
   uu = v.x - bigu.x;
   i = (v.i[LOW_HALF] & 0x000003ff) << 2;
-  if (two52.i[LOW_HALF] == 1023)	/* nx = 0              */
+  if (two52.i[LOW_HALF] == 1023)	/* Exponent of x is 0.  */
     {
       if (i > 1192 && i < 1208)	/* |x-1| < 1.5*2**-10  */
 	{
@@ -296,8 +272,8 @@ log1 (double x, double *delta, double *error)
 							   * (r7 + t * r8)))))
 		- 0.5 * t2 * (t + t1));
 	  res = e1 + e2;
-	  *error = 1.0e-21 * fabs (t);
 	  *delta = (e1 - res) + e2;
+	  /* Max relative error is 1.464844e-24, so accurate to 79.1 bits.  */
 	  return res;
 	}			/* |x-1| < 1.5*2**-10  */
       else
@@ -316,12 +292,12 @@ log1 (double x, double *delta, double *error)
 	  t2 = ((((t - t1) + e) + (ui.x[i + 3] + vj.x[j + 2])) + e2 + e * e
 		* (p2 + e * (p3 + e * p4)));
 	  res = t1 + t2;
-	  *error = 1.0e-24;
 	  *delta = (t1 - res) + t2;
+	  /* Max relative error is 1.0e-24, so accurate to 79.7 bits.  */
 	  return res;
 	}
-    }				/* nx = 0 */
-  else				/* nx != 0   */
+    }
+  else				/* Exponent of x != 0.  */
     {
       eps = u.x - uu;
       nx = (two52.x - two52e.x) + add;
@@ -334,113 +310,13 @@ log1 (double x, double *delta, double *error)
       t2 = ((((t - t1) + e) + nx * ln2b.x + ui.x[i + 3] + e2) + e * e
 	    * (q2 + e * (q3 + e * (q4 + e * (q5 + e * q6)))));
       res = t1 + t2;
-      *error = 1.0e-21;
-      *delta = (t1 - res) + t2;
-      return res;
-    }				/* nx != 0   */
-}
-
-/* Slower but more accurate routine of log.  The returned result is double +
-   DELTA.  The result is bounded by ERROR.  */
-static double
-SECTION
-my_log2 (double x, double *delta, double *error)
-{
-  unsigned int i, j;
-  int m;
-  double uu, vv, eps, nx, e, e1, e2, t, t1, t2, res, add = 0;
-  double ou1, ou2, lu1, lu2, ov, lv1, lv2, a, a1, a2;
-  double y, yy, z, zz, j1, j2, j7, j8;
-#ifndef DLA_FMS
-  double j3, j4, j5, j6;
-#endif
-  mynumber u, v;
-#ifdef BIG_ENDI
-  mynumber /**/ two52 = {{0x43300000, 0x00000000}};	/* 2**52  */
-#else
-# ifdef LITTLE_ENDI
-  mynumber /**/ two52 = {{0x00000000, 0x43300000}};	/* 2**52  */
-# endif
-#endif
-
-  u.x = x;
-  m = u.i[HIGH_HALF];
-  *error = 0;
-  *delta = 0;
-  add = 0;
-  if (m < 0x00100000)
-    {				/* x < 2^-1022 */
-      x = x * t52.x;
-      add = -52.0;
-      u.x = x;
-      m = u.i[HIGH_HALF];
-    }
-
-  if ((m & 0x000fffff) < 0x0006a09e)
-    {
-      u.i[HIGH_HALF] = (m & 0x000fffff) | 0x3ff00000;
-      two52.i[LOW_HALF] = (m >> 20);
-    }
-  else
-    {
-      u.i[HIGH_HALF] = (m & 0x000fffff) | 0x3fe00000;
-      two52.i[LOW_HALF] = (m >> 20) + 1;
-    }
-
-  v.x = u.x + bigu.x;
-  uu = v.x - bigu.x;
-  i = (v.i[LOW_HALF] & 0x000003ff) << 2;
-  /*------------------------------------- |x-1| < 2**-11-------------------------------  */
-  if ((two52.i[LOW_HALF] == 1023) && (i == 1200))
-    {
-      t = x - 1.0;
-      EMULV (t, s3, y, yy, j1, j2, j3, j4, j5);
-      ADD2 (-0.5, 0, y, yy, z, zz, j1, j2);
-      MUL2 (t, 0, z, zz, y, yy, j1, j2, j3, j4, j5, j6, j7, j8);
-      MUL2 (t, 0, y, yy, z, zz, j1, j2, j3, j4, j5, j6, j7, j8);
-
-      e1 = t + z;
-      e2 = ((((t - e1) + z) + zz) + t * t * t
-	    * (ss3 + t * (s4 + t * (s5 + t * (s6 + t * (s7 + t * s8))))));
-      res = e1 + e2;
-      *error = 1.0e-25 * fabs (t);
-      *delta = (e1 - res) + e2;
-      return res;
-    }
-  /*----------------------------- |x-1| > 2**-11  --------------------------  */
-  else
-    {				/*Computing log(x) according to log table                        */
-      nx = (two52.x - two52e.x) + add;
-      ou1 = ui.x[i];
-      ou2 = ui.x[i + 1];
-      lu1 = ui.x[i + 2];
-      lu2 = ui.x[i + 3];
-      v.x = u.x * (ou1 + ou2) + bigv.x;
-      vv = v.x - bigv.x;
-      j = v.i[LOW_HALF] & 0x0007ffff;
-      j = j + j + j;
-      eps = u.x - uu * vv;
-      ov = vj.x[j];
-      lv1 = vj.x[j + 1];
-      lv2 = vj.x[j + 2];
-      a = (ou1 + ou2) * (1.0 + ov);
-      a1 = (a + 1.0e10) - 1.0e10;
-      a2 = a * (1.0 - a1 * uu * vv);
-      e1 = eps * a1;
-      e2 = eps * a2;
-      e = e1 + e2;
-      e2 = (e1 - e) + e2;
-      t = nx * ln2a.x + lu1 + lv1;
-      t1 = t + e;
-      t2 = ((((t - t1) + e) + (lu2 + lv2 + nx * ln2b.x + e2)) + e * e
-	    * (p2 + e * (p3 + e * p4)));
-      res = t1 + t2;
-      *error = 1.0e-27;
       *delta = (t1 - res) + t2;
+      /* Max relative error is 1.0e-21, so accurate to 69.7 bits.  */
       return res;
     }
 }
 
+
 /* This function receives a double x and checks if it is an integer.  If not,
    it returns 0, else it returns 1 if even or -1 if odd.  */
 static int
diff --git a/sysdeps/ieee754/dbl-64/halfulp.c b/sysdeps/ieee754/dbl-64/halfulp.c
deleted file mode 100644
index 0768d8641f..0000000000
--- a/sysdeps/ieee754/dbl-64/halfulp.c
+++ /dev/null
@@ -1,152 +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:halfulp.c                                                */
-/*                                                                      */
-/*  FUNCTIONS:halfulp                                                   */
-/*  FILES NEEDED: mydefs.h dla.h endian.h                               */
-/*                uroot.c                                               */
-/*                                                                      */
-/*Routine halfulp(double x, double y) computes x^y where result does    */
-/*not need rounding. If the result is closer to 0 than can be           */
-/*represented it returns 0.                                             */
-/*     In the following cases the function does not compute anything    */
-/*and returns a negative number:                                        */
-/*1. if the result needs rounding,                                      */
-/*2. if y is outside the interval [0,  2^20-1],                         */
-/*3. if x can be represented by  x=2**n for some integer n.             */
-/************************************************************************/
-
-#include "endian.h"
-#include "mydefs.h"
-#include <dla.h>
-#include <math_private.h>
-
-#ifndef SECTION
-# define SECTION
-#endif
-
-static const int4 tab54[32] = {
-  262143, 11585,  1782, 511, 210, 107, 63, 42,
-  30,     22,     17,   14,  12,  10,  9, 7,
-  7,      6,      5,    5,   5,   4,   4, 4,
-  3,      3,      3,    3,   3,   3,   3, 3
-};
-
-
-double
-SECTION
-__halfulp (double x, double y)
-{
-  mynumber v;
-  double z, u, uu;
-#ifndef DLA_FMS
-  double j1, j2, j3, j4, j5;
-#endif
-  int4 k, l, m, n;
-  if (y <= 0)                 /*if power is negative or zero */
-    {
-      v.x = y;
-      if (v.i[LOW_HALF] != 0)
-	return -10.0;
-      v.x = x;
-      if (v.i[LOW_HALF] != 0)
-	return -10.0;
-      if ((v.i[HIGH_HALF] & 0x000fffff) != 0)
-	return -10;                                     /* if x =2 ^ n */
-      k = ((v.i[HIGH_HALF] & 0x7fffffff) >> 20) - 1023; /* find this n */
-      z = (double) k;
-      return (z * y == -1075.0) ? 0 : -10.0;
-    }
-  /* if y > 0  */
-  v.x = y;
-  if (v.i[LOW_HALF] != 0)
-    return -10.0;
-
-  v.x = x;
-  /*  case where x = 2**n for some integer n */
-  if (((v.i[HIGH_HALF] & 0x000fffff) | v.i[LOW_HALF]) == 0)
-    {
-      k = (v.i[HIGH_HALF] >> 20) - 1023;
-      return (((double) k) * y == -1075.0) ? 0 : -10.0;
-    }
-
-  v.x = y;
-  k = v.i[HIGH_HALF];
-  m = k << 12;
-  l = 0;
-  while (m)
-    {
-      m = m << 1; l++;
-    }
-  n = (k & 0x000fffff) | 0x00100000;
-  n = n >> (20 - l);                       /*   n is the odd integer of y    */
-  k = ((k >> 20) - 1023) - l;               /*   y = n*2**k                   */
-  if (k > 5)
-    return -10.0;
-  if (k > 0)
-    for (; k > 0; k--)
-      n *= 2;
-  if (n > 34)
-    return -10.0;
-  k = -k;
-  if (k > 5)
-    return -10.0;
-
-  /*   now treat x        */
-  while (k > 0)
-    {
-      z = __ieee754_sqrt (x);
-      EMULV (z, z, u, uu, j1, j2, j3, j4, j5);
-      if (((u - x) + uu) != 0)
-	break;
-      x = z;
-      k--;
-    }
-  if (k)
-    return -10.0;
-
-  /* it is impossible that n == 2,  so the mantissa of x must be short  */
-
-  v.x = x;
-  if (v.i[LOW_HALF])
-    return -10.0;
-  k = v.i[HIGH_HALF];
-  m = k << 12;
-  l = 0;
-  while (m)
-    {
-      m = m << 1; l++;
-    }
-  m = (k & 0x000fffff) | 0x00100000;
-  m = m >> (20 - l);                       /*   m is the odd integer of x    */
-
-  /*   now check whether the length of m**n is at most 54 bits */
-
-  if (m > tab54[n - 3])
-    return -10.0;
-
-  /* yes, it is - now compute x**n by simple multiplications  */
-
-  u = x;
-  for (k = 1; k < n; k++)
-    u = u * x;
-  return u;
-}
diff --git a/sysdeps/ieee754/dbl-64/slowpow.c b/sysdeps/ieee754/dbl-64/slowpow.c
deleted file mode 100644
index d7c7fb3eb8..0000000000
--- a/sysdeps/ieee754/dbl-64/slowpow.c
+++ /dev/null
@@ -1,125 +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:slowpow.c                                                 */
-/*                                                                       */
-/* FUNCTION:slowpow                                                      */
-/*                                                                       */
-/*FILES NEEDED:mpa.h                                                     */
-/*             mpa.c mpexp.c mplog.c halfulp.c                           */
-/*                                                                       */
-/* Given two IEEE double machine numbers y,x , routine  computes the     */
-/* correctly  rounded (to nearest) value of x^y. Result calculated  by   */
-/* multiplication (in halfulp.c) or if result isn't accurate enough      */
-/* then routine converts x and y into multi-precision doubles     and    */
-/* calls to mpexp routine                                                */
-/*************************************************************************/
-
-#include "mpa.h"
-#include <math_private.h>
-
-#include <stap-probe.h>
-
-#ifndef SECTION
-# define SECTION
-#endif
-
-void __mpexp (mp_no *x, mp_no *y, int p);
-void __mplog (mp_no *x, mp_no *y, int p);
-double ulog (double);
-double __halfulp (double x, double y);
-
-double
-SECTION
-__slowpow (double x, double y, double z)
-{
-  double res, res1;
-  mp_no mpx, mpy, mpz, mpw, mpp, mpr, mpr1;
-  static const mp_no eps = {-3, {1.0, 4.0}};
-  int p;
-
-  /* __HALFULP returns -10 or X^Y.  */
-  res = __halfulp (x, y);
-
-  /* Return if the result was computed by __HALFULP.  */
-  if (res >= 0)
-    return res;
-
-  /* Compute pow as long double.  This is currently only used by powerpc, where
-     one may get 106 bits of accuracy.  */
-#ifdef USE_LONG_DOUBLE_FOR_MP
-  long double ldw, ldz, ldpp;
-  static const long double ldeps = 0x4.0p-96;
-
-  ldz = __ieee754_logl ((long double) x);
-  ldw = (long double) y *ldz;
-  ldpp = __ieee754_expl (ldw);
-  res = (double) (ldpp + ldeps);
-  res1 = (double) (ldpp - ldeps);
-
-  /* Return the result if it is accurate enough.  */
-  if (res == res1)
-    return res;
-#endif
-
-  /* Or else, calculate using multiple precision.  P = 10 implies accuracy of
-     240 bits accuracy, since MP_NO has a radix of 2^24.  */
-  p = 10;
-  __dbl_mp (x, &mpx, p);
-  __dbl_mp (y, &mpy, p);
-  __dbl_mp (z, &mpz, p);
-
-  /* z = x ^ y
-     log (z) = y * log (x)
-     z = exp (y * log (x))  */
-  __mplog (&mpx, &mpz, p);
-  __mul (&mpy, &mpz, &mpw, p);
-  __mpexp (&mpw, &mpp, p);
-
-  /* Add and subtract EPS to ensure that the result remains unchanged, i.e. we
-     have last bit accuracy.  */
-  __add (&mpp, &eps, &mpr, p);
-  __mp_dbl (&mpr, &res, p);
-  __sub (&mpp, &eps, &mpr1, p);
-  __mp_dbl (&mpr1, &res1, p);
-  if (res == res1)
-    {
-      /* Track how often we get to the slow pow code plus
-	 its input/output values.  */
-      LIBC_PROBE (slowpow_p10, 4, &x, &y, &z, &res);
-      return res;
-    }
-
-  /* If we don't, then we repeat using a higher precision.  768 bits of
-     precision ought to be enough for anybody.  */
-  p = 32;
-  __dbl_mp (x, &mpx, p);
-  __dbl_mp (y, &mpy, p);
-  __dbl_mp (z, &mpz, p);
-  __mplog (&mpx, &mpz, p);
-  __mul (&mpy, &mpz, &mpw, p);
-  __mpexp (&mpw, &mpp, p);
-  __mp_dbl (&mpp, &res, p);
-
-  /* Track how often we get to the uber-slow pow code plus
-     its input/output values.  */
-  LIBC_PROBE (slowpow_p32, 4, &x, &y, &z, &res);
-
-  return res;
-}
diff --git a/sysdeps/ieee754/dbl-64/uexp.h b/sysdeps/ieee754/dbl-64/uexp.h
index a8a023ee80..2edf530b69 100644
--- a/sysdeps/ieee754/dbl-64/uexp.h
+++ b/sysdeps/ieee754/dbl-64/uexp.h
@@ -30,7 +30,7 @@
 #include "mydefs.h"
 
 const static double zero = 0.0, hhuge = 1.0e300, tiny = 1.0e-300,
-err_0 = 1.000014, err_1 = 0.000016;
+err_0 = 1.000014;
 const static int4 bigint = 0x40862002,
              badint = 0x40876000,smallint = 0x3C8fffff;
 const static int4 hugeint = 0x7FFFFFFF, infint = 0x7ff00000;