https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77478
Bug ID: 77478 Summary: Incorrect code generated with -O3, m32, -msse2 and -ffast-math Product: gcc Version: 5.4.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c Assignee: unassigned at gcc dot gnu.org Reporter: gcc_bugzilla at appletonaudio dot com Target Milestone: --- Created attachment 39555 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=39555&action=edit The output of -save-temps Apologies if I've selected the wrong component - I suspect this issue is something wrong in one of the optimization phases, but was not sure what "component" to select. The attached program will crash with a segmentation fault when compiled with the specified arguments. The generated code appears to be generating aligned vector load instructions on a not properly aligned address. I've tried to reduce the program and compiler arguments as much as I can into something which still triggers the behavior. * the exact version of GCC; * the system type; * the options given when GCC was configured/built; Using built-in specs. COLLECT_GCC=gcc COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/5/lto-wrapper Target: x86_64-linux-gnu Configured with: ../src/configure -v --with-pkgversion='Ubuntu 5.4.0-6ubuntu1~16.04.2' --with-bugurl=file:///usr/share/doc/gcc-5/README.Bugs --enable-languages=c,ada,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-5 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-vtable-verify --enable-libmpx --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-5-amd64/jre --enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-5-amd64 --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-5-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 --enable-multilib --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 5.4.0 20160609 (Ubuntu 5.4.0-6ubuntu1~16.04.2) (This GCC was obtained using apt) * the complete command line that triggers the bug; gcc -msse2 -O3 -ffast-math -m32 test.c * the compiler output (error messages, warnings, etc.); and The compiler produces no warnings with -Wextra. When I tried to use the undefined behavior sanitizer (-fsanitize=undefined), the crash vanishes. * the preprocessed file (*.i*) that triggers the bug, generated by adding -save-temps to the complete compilation command, or, in the case of a bug report for the GNAT front end, a complete set of source files (see below). This file is attached and is identical to the .c file which generated it (minus the hash-prefixed lines at the top).