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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`
The codegen crate contains the code to convert from MIR into LLVM IR,
and then from LLVM IR into machine code. In general it contains code
that runs towards the end of the compilation process.
For more information about how codegen works, see the rustc dev guide.