fix fesetenv(FE_DFL_ENV) on mips

[musl] / src / math / fma.c

diff --git a/src/math/fma.c b/src/math/fma.c
index 84868be..741ccd7 100644 (file)
--- a/src/math/fma.c
+++ b/src/math/fma.c
@@ -273,7 +273,7 @@ static inline double add_and_denormalize(double a, double b, int scale)
        if (sum.lo != 0) {
                uhi.f = sum.hi;
                bits_lost = -((int)(uhi.i >> 52) & 0x7ff) - scale + 1;
-               if (bits_lost != 1 ^ (int)(uhi.i & 1)) {
+               if ((bits_lost != 1) ^ (int)(uhi.i & 1)) {
                        /* hibits += (int)copysign(1.0, sum.hi * sum.lo) */
                        ulo.f = sum.lo;
                        uhi.i += 1 - (((uhi.i ^ ulo.i) >> 62) & 2);
@@ -431,12 +431,24 @@ double fma(double x, double y, double z)
                /*
                 * There is no need to worry about double rounding in directed
                 * rounding modes.
-                * TODO: underflow is not raised properly, example in downward rounding:
+                * But underflow may not be raised properly, example in downward rounding:
                 * fma(0x1.000000001p-1000, 0x1.000000001p-30, -0x1p-1066)
                 */
+               double ret;
+#if defined(FE_INEXACT) && defined(FE_UNDERFLOW)
+               int e = fetestexcept(FE_INEXACT);
+               feclearexcept(FE_INEXACT);
+#endif
                fesetround(oround);
                adj = r.lo + xy.lo;
-               return scalbn(r.hi + adj, spread);
+               ret = scalbn(r.hi + adj, spread);
+#if defined(FE_INEXACT) && defined(FE_UNDERFLOW)
+               if (ilogb(ret) < -1022 && fetestexcept(FE_INEXACT))
+                       feraiseexcept(FE_UNDERFLOW);
+               else if (e)
+                       feraiseexcept(FE_INEXACT);
+#endif
+               return ret;
        }
 
        adj = add_adjusted(r.lo, xy.lo);