http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56125
Bug #: 56125
Summary: -O2 -ffast-math generates bad code when dividing a
double by the square of another double.
Classification: Unclassified
Product: gcc
Version: 4.7.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: [email protected]
ReportedBy: [email protected]
Created attachment 29288
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29288
Test program.
XXX@willow:~$ gcc -O0 -o weird weird.c
XXX@willow:~$ ./weird
7.250000
XXX@willow:~$ gcc -O2 -o weird weird.c
XXX@willow:~$ ./weird
7.250000
XXX@willow:~$ gcc -ffast-math -O2 -o weird weird.c
XXX@willow:~$ ./weird
5.126524
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.7/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 4.7.2-5'
--with-bugurl=file:///usr/share/doc/gcc-4.7/README.Bugs
--enable-languages=c,c++,go,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-4.7 --enable-shared --enable-linker-build-id
--with-system-zlib --libexecdir=/usr/lib --without-included-gettext
--enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.7
--libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu
--enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-gnu-unique-object
--enable-plugin --enable-objc-gc --with-arch-32=i586 --with-tune=generic
--enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu
--target=x86_64-linux-gnu
Thread model: posix
gcc version 4.7.2 (Debian 4.7.2-5)
