Sync with upstream FreeBSD libm.

Change-Id: I97e9b23903f1d993d84825806065e85626007d31
diff --git a/libm/upstream-freebsd/lib/msun/src/e_jnf.c b/libm/upstream-freebsd/lib/msun/src/e_jnf.c
index f564aec..c82d5cf 100644
--- a/libm/upstream-freebsd/lib/msun/src/e_jnf.c
+++ b/libm/upstream-freebsd/lib/msun/src/e_jnf.c
@@ -14,11 +14,17 @@
  */
 
 #include <sys/cdefs.h>
-__FBSDID("$FreeBSD$");
+__FBSDID("$FreeBSD: head/lib/msun/src/e_jnf.c 279856 2015-03-10 17:10:54Z kargl $");
+
+/*
+ * See e_jn.c for complete comments.
+ */
 
 #include "math.h"
 #include "math_private.h"
 
+static const volatile float vone = 1, vzero = 0;
+
 static const float
 two   =  2.0000000000e+00, /* 0x40000000 */
 one   =  1.0000000000e+00; /* 0x3F800000 */
@@ -172,10 +178,9 @@
 
 	GET_FLOAT_WORD(hx,x);
 	ix = 0x7fffffff&hx;
-    /* if Y(n,NaN) is NaN */
 	if(ix>0x7f800000) return x+x;
-	if(ix==0) return -one/zero;
-	if(hx<0) return zero/zero;
+	if(ix==0) return -one/vzero;
+	if(hx<0) return vzero/vzero;
 	sign = 1;
 	if(n<0){
 		n = -n;