https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111036
Bug ID: 111036 Summary: Code generation error in handling __builtin_constant_p Product: gcc Version: 13.1.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: bmei at broadcom dot com Target Milestone: --- Compile and run following code #include <stdio.h> #define __align(n) __attribute__((aligned(n))) __attribute__((aligned(32))) static struct { unsigned long long available_cmd_ids_per_core[2]; } _rl2c_cmd_id_data; static inline void __attribute__((always_inline)) foo (void *base, size_t length) { unsigned long int p = (unsigned long int) base; if (__builtin_constant_p(p) && (p & 31) == 0) { printf("constant p && aligned to 32\n"); } else if (__builtin_constant_p(length)) { printf("constant length\n");} else { printf("else\n"); } } int main(int argc, char **argv) { foo(&_rl2c_cmd_id_data, sizeof(*(&_rl2c_cmd_id_data))); return 0; } With gcc 12.1.0 & gcc 13.1.0, I got segmentation fault. With 11.1.0 and below, I got correct result. I examined the dumped tree IR. In einline pass, a __builtin_unreachable is inserted for else if/else branches as the compiler probably thinks __builtin_constant_p(p) & (p&31) is always true. But the later passes think __builtin_constant_p(p) is always false. Therefore all code are optimized away.