It's not used much in a sense that it's applied to very few functions, but it is well known and widely used in limited circumstances. The bugs in LLVM (and GCC)

It's not used much in a sense that it's applied to very few functions, but it is well known and widely used in limited circumstances. The bugs in LLVM (and GCC) are basically because Rust is using aliasing much more widely than it ever has been in most C programs. Take for e.g. this: void add(double *A, double *B, double *C, int N) { for(int i = 0; i < N; i++) { C[i] = A[i] + B[i]; } } You generally wouldn't find many C developers sprinkling restrict in on functions like this, since that function could be useful to someone using add on two overlapping arrays. On the other hand, someone writing a ODE solver in a scientific code might write a function like this, where it would never make sense for the memory locations to overlap: void RHS(double* restrict x, double* restrict xdot, int N, double dt) { for(int i = 0; i < N; i++) { xdot[i] = -x[i]/dt; } } In those sorts of circumstances, it's one of the first performance optimisations you might reach for in your C/C++ toolkit, before starting to look at for e.g. parallelism. It's been in every simulation or mathematical code base I've worked on in 10+ years at various different academic institutions and industry companies.