Simplified the fix in rev.1.3. Instead of using long double for

TWO52[sx] to trick gcc into correctly converting TWO52[sx]+x to double
on assignment to "double w", force a correct assignment by assigning
to *(double *)&w.  This is cleaner and avoids the double rounding
problem on machines that evaluate double expressions in double
precision.  It is not necessary to convert w-TWO52[sx] to double
precision on return as implied in the comment in rev.1.3, since
the difference is exact.

1 files changed, 2 insertions, 8 deletions

diff --git a/lib/msun/src/s_rint.c b/lib/msun/src/s_rint.c
index 2d9b672..0a7bfc4 100644
--- a/lib/msun/src/s_rint.c
+++ b/lib/msun/src/s_rint.c
@@ -27,13 +27,7 @@ static char rcsid[] = "$FreeBSD$";
 #include "math.h"
 #include "math_private.h"
 
-/*
- * TWO23 is long double instead of double to avoid a bug in gcc.  Without
- * this, gcc thinks that TWO23[sx]+x and w-TWO23[sx] already have double
- * precision and doesn't clip them to double precision when they are
- * assigned and returned.
- */
-static const long double
+static const double
 TWO52[2]={
   4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
  -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
@@ -88,6 +82,6 @@ rint(double x)
 	    if((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(j0-20));
 	}
 	INSERT_WORDS(x,i0,i1);
-	w = TWO52[sx]+x;
+	*(volatile double *)&w = TWO52[sx]+x;	/* clip any extra precision */
 	return w-TWO52[sx];
 }