ldbl-128ibm: Copy implementations from ldbl-128 instead of including them

Some files under sysdeps/ieee754/ldbl-128ibm/ are able to reuse the
implementation in sysdeps/ieee754/ldbl-128/ by defining _Float128 to
long double.  This relied on compiler support for _Float128 being
disabled.  On powerpc, such support was disabled by default, however, it
got enabled by default [1] in GCC 8.

This patch copies the implementations from ldbl-128 to ldbl-128ibm.  The
uses of _Float128 and L() are kept intact in this patch and are replaced
with a script in a subsequent patch.

[1] https://gcc.gnu.org/ml/gcc-patches/2017-08/msg01028.html

Tested for powerpc64 and powerpc64le.

	* sysdeps/ieee754/ldbl-128ibm/e_expl.c: Include tables from
	sysdeps/ieee754/ldbl-128ibm.
	* sysdeps/ieee754/ldbl-128ibm/e_j0l.c: Copy contents from the
	equivalent implementation in sysdeps/ieee754/ldbl-128/ instead
	of including it.  Keep _Float128 and L() intact.  These will be
	reviewed by a separate patch.
	* sysdeps/ieee754/ldbl-128ibm/e_j1l.c: Likewise.
	* sysdeps/ieee754/ldbl-128ibm/e_lgammal_r.c: Likewise.
	* sysdeps/ieee754/ldbl-128ibm/s_cbrtl.c: Likewise.
	* sysdeps/ieee754/ldbl-128ibm/t_expl.h: Likewise.

1 files changed, 99 insertions, 5 deletions

diff --git a/sysdeps/ieee754/ldbl-128ibm/s_cbrtl.c b/sysdeps/ieee754/ldbl-128ibm/s_cbrtl.c
index 64bfc46414..615707ca98 100644
--- a/sysdeps/ieee754/ldbl-128ibm/s_cbrtl.c
+++ b/sysdeps/ieee754/ldbl-128ibm/s_cbrtl.c
@@ -1,10 +1,104 @@
-/* Looks like we can use ieee854 s_cbrtl.c as is for IBM extended format. */
-#include <math_ldbl_opt.h>
-#undef weak_alias
-#define weak_alias(n,a)
+/* Implementation of cbrtl.  IBM Extended Precision version.
+   Cephes Math Library Release 2.2: January, 1991
+   Copyright 1984, 1991 by Stephen L. Moshier
+   Adapted for glibc October, 2001.
+
+   This 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.
+
+   This 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 this library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/* This file was copied from sysdeps/ieee754/ldbl-128/e_j0l.c.  */
 
 #define _Float128 long double
 #define L(x) x ## L
 
-#include <sysdeps/ieee754/ldbl-128/s_cbrtl.c>
+#include <math_ldbl_opt.h>
+#include <math.h>
+#include <math_private.h>
+
+static const _Float128 CBRT2 = L(1.259921049894873164767210607278228350570251);
+static const _Float128 CBRT4 = L(1.587401051968199474751705639272308260391493);
+static const _Float128 CBRT2I = L(0.7937005259840997373758528196361541301957467);
+static const _Float128 CBRT4I = L(0.6299605249474365823836053036391141752851257);
+
+
+_Float128
+__cbrtl (_Float128 x)
+{
+  int e, rem, sign;
+  _Float128 z;
+
+  if (!isfinite (x))
+    return x + x;
+
+  if (x == 0)
+    return (x);
+
+  if (x > 0)
+    sign = 1;
+  else
+    {
+      sign = -1;
+      x = -x;
+    }
+
+  z = x;
+ /* extract power of 2, leaving mantissa between 0.5 and 1  */
+  x = __frexpl (x, &e);
+
+  /* Approximate cube root of number between .5 and 1,
+     peak relative error = 1.2e-6  */
+  x = ((((L(1.3584464340920900529734e-1) * x
+	  - L(6.3986917220457538402318e-1)) * x
+	 + L(1.2875551670318751538055e0)) * x
+	- L(1.4897083391357284957891e0)) * x
+       + L(1.3304961236013647092521e0)) * x + L(3.7568280825958912391243e-1);
+
+  /* exponent divided by 3 */
+  if (e >= 0)
+    {
+      rem = e;
+      e /= 3;
+      rem -= 3 * e;
+      if (rem == 1)
+	x *= CBRT2;
+      else if (rem == 2)
+	x *= CBRT4;
+    }
+  else
+    {				/* argument less than 1 */
+      e = -e;
+      rem = e;
+      e /= 3;
+      rem -= 3 * e;
+      if (rem == 1)
+	x *= CBRT2I;
+      else if (rem == 2)
+	x *= CBRT4I;
+      e = -e;
+    }
+
+  /* multiply by power of 2 */
+  x = __ldexpl (x, e);
+
+  /* Newton iteration */
+  x -= (x - (z / (x * x))) * L(0.3333333333333333333333333333333333333333);
+  x -= (x - (z / (x * x))) * L(0.3333333333333333333333333333333333333333);
+  x -= (x - (z / (x * x))) * L(0.3333333333333333333333333333333333333333);
+
+  if (sign < 0)
+    x = -x;
+  return (x);
+}
+
 long_double_symbol (libm, __cbrtl, cbrtl);