https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114415
Bug ID: 114415 Summary: wrong code with -Oz -fno-dce -fno-forward-propagate -flive-range-shrinkage -fweb Product: gcc Version: 14.0 Status: UNCONFIRMED Keywords: wrong-code Severity: normal Priority: P3 Component: target Assignee: unassigned at gcc dot gnu.org Reporter: zsojka at seznam dot cz Target Milestone: --- Host: x86_64-pc-linux-gnu Target: x86_64-pc-linux-gnu Created attachment 57755 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=57755&action=edit reduced testcase Output: $ x86_64-pc-linux-gnu-gcc -Oz -fno-dce -fno-forward-propagate -flive-range-shrinkage -fweb testcase.c -Wno-psabi $ ./a.out Aborted It seems the issue is in: 0x000000000040137e <+214>: movq $0x1,-0x1b0(%rbp) 0x0000000000401389 <+225>: push $0x10 0x000000000040138b <+227>: pop %rcx 0x000000000040138c <+228>: rep movsl %ds:(%rsi),%es:(%rdi) => 0x000000000040138e <+230>: push $0x10 0x0000000000401390 <+232>: mov %rbx,%rdi 0x0000000000401393 <+235>: lea -0xf0(%rbp),%rsi 0x000000000040139a <+242>: pop %rcx (gdb) p $rsp $48 = (void *) 0x7fffffffd3c0 (gdb) p/x $rdi $50 = 0x7fffffffd3c0 that "push" overwrites the destination of the just finished "rep movsd"; this is probably specific to -Oz $ x86_64-pc-linux-gnu-gcc -v Using built-in specs. COLLECT_GCC=/repo/gcc-trunk/binary-latest-amd64/bin/x86_64-pc-linux-gnu-gcc COLLECT_LTO_WRAPPER=/repo/gcc-trunk/binary-trunk-r14-9591-20240321175934-gac2f8c2a367-checking-yes-rtl-df-extra-nobootstrap-amd64/bin/../libexec/gcc/x86_64-pc-linux-gnu/14.0.1/lto-wrapper Target: x86_64-pc-linux-gnu Configured with: /repo/gcc-trunk//configure --enable-languages=c,c++ --enable-valgrind-annotations --disable-nls --enable-checking=yes,rtl,df,extra --disable-bootstrap --with-cloog --with-ppl --with-isl --build=x86_64-pc-linux-gnu --host=x86_64-pc-linux-gnu --target=x86_64-pc-linux-gnu --with-ld=/usr/bin/x86_64-pc-linux-gnu-ld --with-as=/usr/bin/x86_64-pc-linux-gnu-as --enable-libsanitizer --disable-libstdcxx-pch --prefix=/repo/gcc-trunk//binary-trunk-r14-9591-20240321175934-gac2f8c2a367-checking-yes-rtl-df-extra-nobootstrap-amd64 Thread model: posix Supported LTO compression algorithms: zlib zstd gcc version 14.0.1 20240321 (experimental) (GCC)