https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107767
Bug ID: 107767 Summary: GCC has some problems in optimizer of trivial case Product: gcc Version: 13.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: regression Assignee: unassigned at gcc dot gnu.org Reporter: socketpair at gmail dot com Target Milestone: --- See https://godbolt.org/z/rTfTondfP ``` #include <stdint.h> int firewall(const uint8_t *restrict data) { const uint8_t ip_proto = *data; const uint16_t dst_port = *((const uint16_t *)data + 32); if (ip_proto == 17 && dst_port == 15) return 1; if (ip_proto == 17 && dst_port == 23) return 1; if (ip_proto == 17 && dst_port == 47) return 1; if (ip_proto == 17 && dst_port == 45) return 1; if (ip_proto == 17 && dst_port == 42) return 1; if (ip_proto == 17 && dst_port == 1) return 1; if (ip_proto == 17 && dst_port == 2) return 1; if (ip_proto == 17 && dst_port == 3) return 1; return 0; } int firewall2(const uint8_t *restrict data) { const uint16_t dst_port = *((const uint16_t *)data + 32); if (dst_port == 15) return 1; if (dst_port == 23) return 1; if (dst_port == 47) return 1; if (dst_port == 45) return 1; if (dst_port == 42) return 1; if (dst_port == 1) return 1; if (dst_port == 2) return 1; if (dst_port == 3) return 1; return 0; } ``` Compile with -Os. Second function IS NOT minimal, obviously. It's a bug. GCC 12.2 does not have it.