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);
/*
* 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);