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authorJoseph Myers <joseph@codesourcery.com>2012-11-22 15:00:35 +0000
committerJoseph Myers <joseph@codesourcery.com>2012-11-22 15:00:35 +0000
commitc60d3bf2fa54298f2dcdea1cceda63e0c0b14ae3 (patch)
tree80202dcf5552e575932f18ea1d9ed0cb3dfa42c8
parentef1e0867c0f6b1a39625f45aa8a8a9d83fe739be (diff)
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Fix sign of inexact zero results for ldbl-128ibm fmal.
-rw-r--r--ChangeLog4
-rw-r--r--sysdeps/ieee754/ldbl-128ibm/s_fmal.c8
2 files changed, 11 insertions, 1 deletions
diff --git a/ChangeLog b/ChangeLog
index ff04e57a4e..dc6704421e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2012-11-22  Joseph Myers  <joseph@codesourcery.com>
 
+	[BZ #14645]
+	* sysdeps/ieee754/ldbl-128ibm/s_fmal.c (__fmal): Compute result as
+	x * y if x and y are nonzero and z is zero.
+
 	[BZ #14811]
 	* sysdeps/ieee754/ldbl-128ibm/e_powl.c (__ieee754_powl): Saturate
 	nonzero exponents with absolute value below 0x1p-117 to +/-
diff --git a/sysdeps/ieee754/ldbl-128ibm/s_fmal.c b/sysdeps/ieee754/ldbl-128ibm/s_fmal.c
index a868b8d514..6706eb20ed 100644
--- a/sysdeps/ieee754/ldbl-128ibm/s_fmal.c
+++ b/sysdeps/ieee754/ldbl-128ibm/s_fmal.c
@@ -1,5 +1,5 @@
 /* Compute x * y + z as ternary operation.
-   Copyright (C) 2011 Free Software Foundation, Inc.
+   Copyright (C) 2011-2012 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Contributed by David Flaherty <flaherty@linux.vnet.ibm.com>.
 
@@ -29,6 +29,12 @@ __fmal (long double x, long double y, long double z)
        if ((finite ((double)x) && finite ((double)y)) && isinf ((double)z))
                return (z);
 
+       /* If z is zero and x are y are nonzero, compute the result
+	  as x * y to avoid the wrong sign of a zero result if x * y
+	  underflows to 0.  */
+       if (z == 0 && x != 0 && y != 0)
+	 return x * y;
+
        return (x * y) + z;
 }
 #ifdef IS_IN_libm