From 8ec5b01346114da38e806ca1867da688d3a360e2 Mon Sep 17 00:00:00 2001
From: Joseph Myers <joseph@codesourcery.com>
Date: Sat, 29 Sep 2012 18:31:54 +0000
Subject: Fix sign of exact zero return from fma (bug 14638).

---
 sysdeps/ieee754/dbl-64/s_fma.c  | 5 +++++
 sysdeps/ieee754/dbl-64/s_fmaf.c | 7 +++++++
 2 files changed, 12 insertions(+)

(limited to 'sysdeps/ieee754/dbl-64')

diff --git a/sysdeps/ieee754/dbl-64/s_fma.c b/sysdeps/ieee754/dbl-64/s_fma.c
index ce3bd36fac..c9809fb180 100644
--- a/sysdeps/ieee754/dbl-64/s_fma.c
+++ b/sysdeps/ieee754/dbl-64/s_fma.c
@@ -128,6 +128,11 @@ __fma (double x, double y, double z)
       y = v.d;
       z = w.d;
     }
+
+  /* Ensure correct sign of exact 0 + 0.  */
+  if (__builtin_expect ((x == 0 || y == 0) && z == 0, 0))
+    return x * y + z;
+
   /* Multiplication m1 + m2 = x * y using Dekker's algorithm.  */
 #define C ((1 << (DBL_MANT_DIG + 1) / 2) + 1)
   double x1 = x * C;
diff --git a/sysdeps/ieee754/dbl-64/s_fmaf.c b/sysdeps/ieee754/dbl-64/s_fmaf.c
index e7a0650f0f..a4f12d9f76 100644
--- a/sysdeps/ieee754/dbl-64/s_fmaf.c
+++ b/sysdeps/ieee754/dbl-64/s_fmaf.c
@@ -32,8 +32,15 @@ float
 __fmaf (float x, float y, float z)
 {
   fenv_t env;
+
   /* Multiplication is always exact.  */
   double temp = (double) x * (double) y;
+
+  /* Ensure correct sign of an exact zero result by performing the
+     addition in the original rounding mode in that case.  */
+  if (temp == -z)
+    return (float) temp + z;
+
   union ieee754_double u;
 
   libc_feholdexcept_setround (&env, FE_TOWARDZERO);
-- 
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