https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82898
Martin Sebor <msebor at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |RESOLVED See Also| |https://gcc.gnu.org/bugzill | |a/show_bug.cgi?id=93745 Resolution|--- |INVALID --- Comment #6 from Martin Sebor <msebor at gcc dot gnu.org> --- Just to clarify, since I keep forgetting this myself. The memmove -> memcpy transformation for the test case isn't viable in GCC because the middle end doesn't distinguish between the C test case in comment #3 and the following valid C++ equivalent that changes the dynamic type of i[0] from int to float: void* operator new (__SIZE_TYPE__, void *p) { return p; } void foo(int* i, const float* f) { // i[0] = f[0]; // in C implies i != f new (&i[0]) float (f[0]); // in C++ doesn't rule out that i == f __builtin_memmove(i, f, 1024*1024); } (pr93745 discusses the same limitation.) But even if GCC could make the assumption that i != f, it still wouldn't be safe to transform he memmove call to memcpy because the overlap between the two arrays could be inexact, as in: void bar (void) { float *p = new float[1024 * 1024 + 1]{ }; foo ((int*)p, p + 1); } With that, I think this report can be resolved.