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816f098464
add a fallback implementation for the `prefetch_*` intrinsics related ACP: https://github.com/rust-lang/libs-team/issues/638 The fallback is to just ignore the arguments. That is a valid implementation because this intrinsic is just a hint. I also added the `miri::intrinsic_fallback_is_spec` annotation, so that miri now supports these operations. A prefetch intrinsic call is valid on any pointer. (specifically LLVM guarantees this https://llvm.org/docs/LangRef.html#llvm-prefetch-intrinsic) Next, I made the `LOCALITY` argument a const generic. That argument must be const (otherwise LLVM crashes), but that was not reflected in the type. Finally, with these changes, the intrinsic can be safe and `const` (a prefetch at const evaluation time is just a no-op). cc `@Amanieu` r? `@RalfJung`