http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51672
Bug #: 51672
Summary: The optimization flags O2 & O3 produces wrong code
Classification: Unclassified
Product: gcc
Version: 4.2.1
Status: UNCONFIRMED
Severity: critical
Priority: P3
Component: c++
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: benme...@hotmail.com
Created attachment 26180
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=26180
preprocessed file
Compiling with the optimization flags O2 & O3 produces wrong code & wrong
results. But with the flag O1 or O2, the program output the correct results :
3
1
2
0
O2 & O3 flags output :
65535
1
2
0
Compiled by : g++ -g -O3 -W -Wall -mtune=native -march=native -msse3
test_all.cpp -o test_all
Using :
Using built-in specs.
Target: x86_64-suse-linux
Configured with: ../configure --enable-threads=posix --prefix=/usr
--with-local-prefix=/usr/local --infodir=/usr/share/info
--mandir=/usr/share/man --libdir=/usr/lib64 --libexecdir=/usr/lib64
--enable-languages=c,c++,objc,fortran,obj-c++,java,ada
--enable-checking=release --with-gxx-include-dir=/usr/include/c++/4.2.1
--enable-ssp --disable-libssp --disable-libgcj --with-slibdir=/lib64
--with-system-zlib --enable-shared --enable-__cxa_atexit
--enable-libstdcxx-allocator=new --disable-libstdcxx-pch --program-suffix=-4.2
--enable-version-specific-runtime-libs --without-system-libunwind
--with-cpu=generic --host=x86_64-suse-linux
Thread model: posix
gcc version 4.2.1 (SUSE Linux)
The wrong assembly part marked by ! with (-O3):
400b0a: 48 ba 0f 00 0f 00 0f mov $0xf000f000f000f,%rdx
400b11: 00 0f 00
400b14: 48 33 11 xor (%rcx),%rdx
! 400b17: 66 c7 04 41 0f 00 movw $0xf,(%rcx,%rax,2) "Insert
function"
400b1d: 66 83 fa 01 cmp $0x1,%dx
400b21: 48 89 d0 mov %rdx,%rax
