From 3fc5a433e95a01aad0785ed32af6fb2fc2436998 Mon Sep 17 00:00:00 2001 From: Bruce Evans Date: Sat, 3 Dec 2005 07:38:35 +0000 Subject: [PATCH] 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. --- lib/msun/src/s_rint.c | 10 ++-------- 1 file changed, 2 insertions(+), 8 deletions(-) diff --git a/lib/msun/src/s_rint.c b/lib/msun/src/s_rint.c index 2d9b672be07..0a7bfc47a43 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]; }