https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65709
Bug ID: 65709 Summary: [5 Regression] Bad code for LZ4 decompression with -O3 on x86_64 Product: gcc Version: 5.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: e...@coeus-group.com Created attachment 35266 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35266&action=edit Test data With GCC 5 at -O3 on x86_64 some inputs to LZ4 will generate a segfault when decompressing. This doesn't happen with GCC 4.9, or -O2. It does happen with -O2 -ftree-loop-vectorize -fvect-cost-model=dynamic. I have tested gcc-5.0.0-0.21.fc22.x86_64 from Fedora 22, as well as SVN revision 221940. To trigger the segfault pass the attached input (sum.lz4) as the only command line argument to the preprocessed test case.