I'm not sure it's as rare as you make it out to be - AFAIK most compilers that support restrict declare malloc() and new to return restrict pointers, so in

I'm not sure it's as rare as you make it out to be - AFAIK most compilers that support restrict declare malloc() and new to return restrict pointers, so int *x = malloc(100), *y = malloc(100); followed by some loop should be able to spot that x and y are not aliased. It should also be able to propagate the restrict as pointers are passed around, at least to some extent.