https://gcc.gnu.org/bugzilla/show_bug.cgi?id=32667
--- Comment #44 from Rich Felker <bugdal at aerifal dot cx> --- My naive expectation is that "if ((uintptr_t)src == 0x400400)" is and should be UB, but I may be misremembering the details of the formalism by which the spec for restrict is implemented. If so, that's kinda a help, but I still think you would want to remove restrict from the arguments and apply it later, so that the fast-path head/tail copies can avoid any branch, and the check for equality can be deferred until it's known that there's a "body remainder" to copy. That's the part where you really want the benefits of restrict anyway -- without restrict it's not vectorizable because the compiler has to assume there might be nonexact overlap, in which case reordering the loads and stores in any way could change the result.
