simplify vasprintf implementation

[musl] / src / math / fma.c

diff --git a/src/math/fma.c b/src/math/fma.c
index 1b1c132..02f5c86 100644 (file)
--- a/src/math/fma.c
+++ b/src/math/fma.c
@@ -232,16 +232,16 @@ static inline struct dd dd_add(double a, double b)
 static inline double add_adjusted(double a, double b)
 {
        struct dd sum;
-       uint64_t hibits, lobits;
+       union {double f; uint64_t i;} uhi, ulo;
 
        sum = dd_add(a, b);
        if (sum.lo != 0) {
-               EXTRACT_WORD64(hibits, sum.hi);
-               if ((hibits & 1) == 0) {
+               uhi.f = sum.hi;
+               if ((uhi.i & 1) == 0) {
                        /* hibits += (int)copysign(1.0, sum.hi * sum.lo) */
-                       EXTRACT_WORD64(lobits, sum.lo);
-                       hibits += 1 - ((hibits ^ lobits) >> 62);
-                       INSERT_WORD64(sum.hi, hibits);
+                       ulo.f = sum.lo;
+                       uhi.i += 1 - ((uhi.i ^ ulo.i) >> 62);
+                       sum.hi = uhi.f;
                }
        }
        return (sum.hi);
@@ -255,7 +255,7 @@ static inline double add_adjusted(double a, double b)
 static inline double add_and_denormalize(double a, double b, int scale)
 {
        struct dd sum;
-       uint64_t hibits, lobits;
+       union {double f; uint64_t i;} uhi, ulo;
        int bits_lost;
 
        sum = dd_add(a, b);
@@ -271,13 +271,13 @@ static inline double add_and_denormalize(double a, double b, int scale)
         * break the ties manually.
         */
        if (sum.lo != 0) {
-               EXTRACT_WORD64(hibits, sum.hi);
-               bits_lost = -((int)(hibits >> 52) & 0x7ff) - scale + 1;
-               if (bits_lost != 1 ^ (int)(hibits & 1)) {
+               uhi.f = sum.hi;
+               bits_lost = -((int)(uhi.i >> 52) & 0x7ff) - scale + 1;
+               if (bits_lost != 1 ^ (int)(uhi.i & 1)) {
                        /* hibits += (int)copysign(1.0, sum.hi * sum.lo) */
-                       EXTRACT_WORD64(lobits, sum.lo);
-                       hibits += 1 - (((hibits ^ lobits) >> 62) & 2);
-                       INSERT_WORD64(sum.hi, hibits);
+                       ulo.f = sum.lo;
+                       uhi.i += 1 - (((uhi.i ^ ulo.i) >> 62) & 2);
+                       sum.hi = uhi.f;
                }
        }
        return scalbn(sum.hi, scale);
@@ -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);