Bug#582787: gcc-4.4: Test tstdiomisc fails when multiplication of NAN by -1 results in NAN again.
----- Forwarded message from Carlos O'Donell <email@example.com> -----
Date: Sat, 22 May 2010 22:58:18 -0400
From: Carlos O'Donell <firstname.lastname@example.org>
To: John David Anglin <email@example.com>,
Debian HPPA Port List <firstname.lastname@example.org>,
Subject: Test tstdiomisc fails when multiplication of NAN by -1 results in NAN again.
The following testcase is an example of code used in a glibc testcase.
I'm trying hard to shake out the bugs in the glibc testsuite for
debian, and one testsuite failure looks like a compiler issue.
The expected behaviour is for the testcase to print the raw IEEE754
value of -NAN.
The observed behaviour, when -DALT is on the command line, is that the
testcase prints the incorrect raw value e.g. NAN.
GCC 4.4.3 in debian doesn't compile this code correctly. Could you
have a loot at my analysis and tell me if you have seen this before?
It seems like it should work (even if fr22 is -1.875), since the sign
of the output NAN is the XOR of the signs of the inputs, therefore "-
XOR + = -" and the the result should be -NAN, but it's not, it's NAN?
PA-RISC 2.0 Architecture, Floating Coprocessor 8-23 "Operations With
NaNs", and 8-24 "Sign Bit" can be referenced for information on NANs.
After the multiplication fr22 still contains NAN, and that is what is
printed instead of the expected result of -NAN.
Any idea what is going on here? Thanks for your help.
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