http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60454
Bug ID: 60454 Summary: Code mistakenly detected as doing bswap Product: gcc Version: 4.9.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: thomas.preudhomme at arm dot com Created attachment 32296 --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=32296&action=edit Testcase for bswap incorrect detection Optimization pass optimize_bswap in tree-ssa-math-opts.c incorrectly detect a bswap being performed in certain cases, leading to wrong code being generated. Please find attached a testcase that exhibit the problem. Compile with trunk gcc with gcc -O2 -fdump-tree-bswap -c testcase.c and observe that testcase.c.*bswap contains the string "32 bit bswap implementation found at" while the code does not perform a byte swap. This test was tried on an Ubuntu "13.10 (saucy) with 4.8.1 and trunk gcc. gcc 4.8.1 was configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro 4.8.1-10ubuntu9' --with-bugurl=file:///usr/share/doc/gcc-4.8/README.Bugs --enable-languages=c,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.8 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.8 --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-gnu-unique-object --enable-plugin --with-system-zlib --disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.8-amd64/jre --enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.8-amd64 --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.8-amd64 --with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar --enable-objc-gc --enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu while trunk gcc was configured with: ../src/configure --prefix=../install --target=arm-none-eabi --enable-languages=c,c++ --with-mode=thumb --with-cpu=cortex-m3 --with-newlib --with-headers=../src/newlib/libc/include --enable-newlib-register-fini --disable-newlib-supplied-syscalls --disable-multilib --with-libexpat --with-system-zlib --disable-gdbtk --enable-plugins --disable-libgomp --disable-libmudflap --disable-libquadmath --disable-libssp --disable-libstdcxx-pch --disable-nls --disable-rda --disable-sid --disable-tui --disable-utils --disable-werror --disable-fixed-point I'm currently cleaning a patch to solve this issue. Best regards.