https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111797
Bug ID: 111797 Summary: Code generation of -march=znver2 -O3 includes frame pointer Product: gcc Version: 13.1.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: target Assignee: unassigned at gcc dot gnu.org Reporter: paulf at free dot fr Target Milestone: --- I was a bit surprised recently when I (unintentinally) ran perf record on the exe that I work on with an -O3 build without -fno-omit-frame-pointer and I could see the callstacks. The function prolog that I see is 0000000000000000 <function>: 0: 4c 8d 54 24 08 lea 0x8(%rsp),%r10 5: 48 83 e4 e0 and $0xffffffffffffffe0,%rsp 9: 41 ff 72 f8 push -0x8(%r10) d: 55 push %rbp e: 48 89 e5 mov %rsp,%rbp 11: 41 57 push %r15 13: 41 56 push %r14 15: 41 55 push %r13 17: 41 54 push %r12 19: 41 52 push %r10 1b: 53 push %rbx 1c: 49 89 ce mov %rcx,%r14 1f: 48 81 ec 40 10 00 00 sub $0x1040,%rsp I asked on SO and got pointed to this post https://stackoverflow.com/questions/45423338/whats-up-with-gcc-weird-stack-manipulation-when-it-wants-extra-stack-alignment That problem seems to be fixed https://godbolt.org/z/qc6fqb5hn I can't post the source code as it is proprietary, and it doesn't seem to reproduce with trivial examples (the function that I tried is 23kloc plus it #includes other stuff). I was able to reproduce the problem with the following steps (Valgrind chosen because I'm one of the maintainers and I'm in the habit of building it). git clone https://sourceware.org/git/valgrind.git march_zen2 cd march_zen2 ./autogen.sh ./configure CFLAGS=-march=znver2 make -j 16 objdump -d --disassemble=mc_pre_clo_init mc_pre_clo_init .in_place/memcheck-amd64-linux | less That shows 000000005800c220 <mc_pre_clo_init>: 5800c220: 41 55 push %r13 5800c222: bf 8c 65 1d 58 mov $0x581d658c,%edi 5800c227: 4c 8d 6c 24 10 lea 0x10(%rsp),%r13 5800c22c: 48 83 e4 e0 and $0xffffffffffffffe0,%rsp 5800c230: 41 ff 75 f8 push -0x8(%r13) 5800c234: 55 push %rbp 5800c235: 48 89 e5 mov %rsp,%rbp 5800c238: 41 55 push %r13 5800c23a: 48 83 ec 08 sub $0x8,%rsp which I believe illustrates the same problem. mc_pre_clo_init looks like this static void mc_pre_clo_init(void) { VG_(details_name) ("Memcheck"); VG_(details_version) (NULL); VG_(details_description) ("a memory error detector"); VG_(details_copyright_author)( "Copyright (C) 2002-2022, and GNU GPL'd, by Julian Seward et al."); VG_(details_bug_reports_to) (VG_BUGS_TO); VG_ is a macro that implements a kind of C namespace. The functions are all outputting the memcheck startup banner. I think that I understand that there is a need for a 32byte-aligned stack and also to shuffle the return address. Is it really necessary to also use the frame pointer?