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.
