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author | bde <bde@FreeBSD.org> | 2005-12-03 07:38:35 +0000 |
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committer | bde <bde@FreeBSD.org> | 2005-12-03 07:38:35 +0000 |
commit | 7aaf0755d7de77c7044d1b1d0bac2dc4d57a5ead (patch) | |
tree | 1009ca5e1b2fffe19f88b347297c125a58f00e30 /lib | |
parent | 2e834acd9c22a16214cd4778d549130f052dee8b (diff) | |
download | FreeBSD-src-7aaf0755d7de77c7044d1b1d0bac2dc4d57a5ead.zip FreeBSD-src-7aaf0755d7de77c7044d1b1d0bac2dc4d57a5ead.tar.gz |
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.
Diffstat (limited to 'lib')
-rw-r--r-- | lib/msun/src/s_rint.c | 10 |
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]; } |