Fix a regression introduced in r226371: When the high part of x*y

exactly cancels with z, return the low part of x*y instead of
discarding it.

2 files changed, 6 insertions, 6 deletions

diff --git a/lib/msun/src/s_fma.c b/lib/msun/src/s_fma.c
index 9cb0ddc..dfbd13c 100644
--- a/lib/msun/src/s_fma.c
+++ b/lib/msun/src/s_fma.c
@@ -250,6 +250,8 @@ fma(double x, double y, double z)
 	xy = dd_mul(xs, ys);
 	r = dd_add(xy.hi, zs);
 
+	spread = ex + ey;
+
 	if (r.hi == 0.0) {
 		/*
 		 * When the addends cancel to 0, ensure that the result has
@@ -257,11 +259,9 @@ fma(double x, double y, double z)
 		 */
 		fesetround(oround);
 		volatile double vzs = zs; /* XXX gcc CSE bug workaround */
-		return (xy.hi + vzs);
+		return (xy.hi + vzs + ldexp(xy.lo, spread));
 	}
 
-	spread = ex + ey;
-
 	if (oround != FE_TONEAREST) {
 		/*
 		 * There is no need to worry about double rounding in directed
diff --git a/lib/msun/src/s_fmal.c b/lib/msun/src/s_fmal.c
index 59fa6cd..c2a6913 100644
--- a/lib/msun/src/s_fmal.c
+++ b/lib/msun/src/s_fmal.c
@@ -238,6 +238,8 @@ fmal(long double x, long double y, long double z)
 	xy = dd_mul(xs, ys);
 	r = dd_add(xy.hi, zs);
 
+	spread = ex + ey;
+
 	if (r.hi == 0.0) {
 		/*
 		 * When the addends cancel to 0, ensure that the result has
@@ -245,11 +247,9 @@ fmal(long double x, long double y, long double z)
 		 */
 		fesetround(oround);
 		volatile long double vzs = zs; /* XXX gcc CSE bug workaround */
-		return (xy.hi + vzs);
+		return (xy.hi + vzs + ldexpl(xy.lo, spread));
 	}
 
-	spread = ex + ey;
-
 	if (oround != FE_TONEAREST) {
 		/*
 		 * There is no need to worry about double rounding in directed