From 9a18258bbd90815fea0eeabea8e363de469464b4 Mon Sep 17 00:00:00 2001
From: Bruno Haible <bruno@clisp.org>
Date: Fri, 30 Mar 2007 00:19:34 +0000
Subject: [PATCH] Set the FPU control word as needed for 'long double'
 computations.

---
 ChangeLog      |  7 +++++++
 lib/ldexpl.c   | 37 ++++++++++++++++++++++++++-----------
 modules/ldexpl |  1 +
 3 files changed, 34 insertions(+), 11 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 7c42d3bbe..70487b307 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,12 @@
 2007-03-29  Bruno Haible  <bruno@clisp.org>
 
+	* lib/ldexpl.c: Include fpucw.h.
+	(ldexpl): Use BEGIN/END_LONG_DOUBLE_ROUNDING. Skip the last unneeded
+	multiplication.
+	* modules/ldexpl (Depends-on): Add fpucw.
+
+2007-03-29  Bruno Haible  <bruno@clisp.org>
+
 	* modules/ldexpl: New file.
 	* m4/ldexpl.m4: New file.
 	* lib/math_.h (ldexpl): Define to a replacement if REPLACE_LDEXPL is
diff --git a/lib/ldexpl.c b/lib/ldexpl.c
index f85847b24..bb16be66b 100644
--- a/lib/ldexpl.c
+++ b/lib/ldexpl.c
@@ -25,6 +25,7 @@
 #include <math.h>
 
 #include <float.h>
+#include "fpucw.h"
 #include "isnanl.h"
 
 long double
@@ -32,22 +33,36 @@ ldexpl(long double x, int exp)
 {
   long double factor;
   int bit;
+  DECL_LONG_DOUBLE_ROUNDING
 
-  /* Check for zero, nan and infinity. */
-  if (isnanl (x) || x + x == x)
-    return x;
+  BEGIN_LONG_DOUBLE_ROUNDING ();
 
-  if (exp < 0)
+  /* Check for zero, nan and infinity. */
+  if (!(isnanl (x) || x + x == x))
     {
-      exp = -exp;
-      factor = 0.5L;
+      if (exp < 0)
+	{
+	  exp = -exp;
+	  factor = 0.5L;
+	}
+      else
+	factor = 2.0L;
+
+      if (exp > 0)
+	for (bit = 1;;)
+	  {
+	    /* Invariant: Here bit = 2^i, factor = 2^-2^i or = 2^2^i,
+	       and bit <= exp.  */ 
+	    if (exp & bit)
+	      x *= factor;
+	    bit <<= 1;
+	    if (bit > exp)
+	      break;
+	    factor = factor * factor;
+	  }
     }
-  else
-    factor = 2.0L;
 
-  for (bit = 1; bit <= exp; bit <<= 1, factor *= factor)
-    if (exp & bit)
-      x *= factor;
+  END_LONG_DOUBLE_ROUNDING ();
 
   return x;
 }
diff --git a/modules/ldexpl b/modules/ldexpl
index c89187a50..1d759d02b 100644
--- a/modules/ldexpl
+++ b/modules/ldexpl
@@ -8,6 +8,7 @@ m4/ldexpl.m4
 Depends-on:
 math
 isnanl-nolibm
+fpucw
 
 configure.ac:
 gl_FUNC_LDEXPL
-- 
2.11.0