X-Git-Url: http://nsz.repo.hu/git/?p=musl;a=blobdiff_plain;f=src%2Fmath%2Ffma.c;h=17f1cdcc39bc2a7671b99dbeb7d107ee7973d505;hp=5fb9540601c520dac6ce9a519e8c9abe91aed7d7;hb=8bb181622222f2ee3462c8b021bcae4fcdbbd37a;hpb=634c3a63027aa4a693b64fae0e2f6e1635558e93

diff --git a/src/math/fma.c b/src/math/fma.c
index 5fb95406..17f1cdcc 100644
--- a/src/math/fma.c
+++ b/src/math/fma.c
@@ -41,7 +41,7 @@ static void mul(long double *hi, long double *lo, long double x, long double y)
 
 /*
 assume (long double)(hi+lo) == hi
-return an adjusted hi so that rounding it to double is correct
+return an adjusted hi so that rounding it to double (or less) precision is correct
 */
 static long double adjust(long double hi, long double lo)
 {
@@ -55,17 +55,25 @@ static long double adjust(long double hi, long double lo)
 	ulo.x = lo;
 	if (uhi.bits.s == ulo.bits.s)
 		uhi.bits.m++;
-	else
+	else {
 		uhi.bits.m--;
+		/* handle underflow and take care of ld80 implicit msb */
+		if (uhi.bits.m == (uint64_t)-1/2) {
+			uhi.bits.m *= 2;
+			uhi.bits.e--;
+		}
+	}
 	return uhi.x;
 }
 
+/* adjusted add so the result is correct when rounded to double (or less) precision */
 static long double dadd(long double x, long double y)
 {
 	add(&x, &y, x, y);
 	return adjust(x, y);
 }
 
+/* adjusted mul so the result is correct when rounded to double (or less) precision */
 static long double dmul(long double x, long double y)
 {
 	mul(&x, &y, x, y);
@@ -81,6 +89,7 @@ static int getexp(long double x)
 
 double fma(double x, double y, double z)
 {
+	#pragma STDC FENV_ACCESS ON
 	long double hi, lo1, lo2, xy;
 	int round, ez, exy;
 
@@ -298,6 +307,7 @@ static inline struct dd dd_mul(double a, double b)
  */
 double fma(double x, double y, double z)
 {
+	#pragma STDC FENV_ACCESS ON
 	double xs, ys, zs, adj;
 	struct dd xy, r;
 	int oround;