http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56828
Bug #: 56828
Summary: [PowerPC] Type cast of sNaN value
Classification: Unclassified
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: minor
Priority: P3
Component: target
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: tschwi...@gcc.gnu.org
Target: powerpc
Created attachment 29791
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29791
snan.c
On PowerPC, in versions of GCC up to at least 4.7.2, a type cast -- which
is a IEEE 754-2008 general-computational convertFormat operation (IEEE
754-2008, 5.4.2) -- does not turn a sNaN into a qNaN (whilst raising an
INVALID exception), which is contrary to IEEE 754-2008 5.1 and 7.2.
See the attached snan.c, for which I get for powerpc-linux-gnu-gcc -m64
(additionally specifying -fsignaling-nans doesn't make a difference):
7ff40000 0 0 0
7ff40000 0
7ff40000 0
7fe00000
7fa00000
The second like should have been: 7ffc0000 0 (or
similar; top-most fraction bit (0x0008000) set).
See also the discussion in
<http://news.gmane.org/find-root.php?message_id=%3c5151E427.1080106%40linux.vnet.ibm.com%3e>
and thereabouts, and the SNAN_TESTS_TYPE_CAST usage in glibc commit
572676160d5639edc0ecb663147bd291841458d1,
<http://sourceware.org/git/?p=glibc.git;a=commitdiff;h=572676160d5639edc0ecb663147bd291841458d1>.
