https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87813
--- Comment #9 from Martin Sebor <msebor at gcc dot gnu.org> --- (In reply to Aldy Hernandez from comment #6) I agree, but it's just a small subset of such cases. There are many optimizing transformations that GCC does at -O0 that affect the IL later on: calls to library built-ins are folded into other library calls (strcpy to memcpy), or to MEM_REFs (memcpy), or even to constants (strlen). For example: int f (void) { return __builtin_strlen ("123"); }