Add fine-grained LLVM CFI support to the Rust compiler

This commit improves the LLVM Control Flow Integrity (CFI) support in
the Rust compiler by providing forward-edge control flow protection for
Rust-compiled code only by aggregating function pointers in groups
identified by their return and parameter types.

Forward-edge control flow protection for C or C++ and Rust -compiled
code "mixed binaries" (i.e., for when C or C++ and Rust -compiled code
share the same virtual address space) will be provided in later work as
part of this project by identifying C char and integer type uses at the
time types are encoded (see Type metadata in the design document in the
tracking issue #89653).

LLVM CFI can be enabled with -Zsanitizer=cfi and requires LTO (i.e.,
-Clto).

compiler/rustc_symbol_mangling/src/lib.rs

@@ -102,9 +102,8 @@ use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrs;
 use rustc_middle::mir::mono::{InstantiationMode, MonoItem};
 use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::subst::SubstsRef;
-use rustc_middle::ty::{self, Instance, Ty, TyCtxt};
+use rustc_middle::ty::{self, Instance, TyCtxt};
 use rustc_session::config::SymbolManglingVersion;
-use rustc_target::abi::call::FnAbi;
 
 use tracing::debug;
 
@@ -112,6 +111,7 @@ mod legacy;
 mod v0;
 
 pub mod test;
+pub mod typeid;
 
 /// This function computes the symbol name for the given `instance` and the
 /// given instantiating crate. That is, if you know that instance X is
@@ -150,11 +150,6 @@ fn symbol_name_provider<'tcx>(tcx: TyCtxt<'tcx>, instance: Instance<'tcx>) -> ty
     ty::SymbolName::new(tcx, &symbol_name)
 }
 
-/// This function computes the typeid for the given function ABI.
-pub fn typeid_for_fnabi<'tcx>(tcx: TyCtxt<'tcx>, fn_abi: &FnAbi<'tcx, Ty<'tcx>>) -> String {
-    v0::mangle_typeid_for_fnabi(tcx, fn_abi)
-}
-
 pub fn typeid_for_trait_ref<'tcx>(
     tcx: TyCtxt<'tcx>,
     trait_ref: ty::PolyExistentialTraitRef<'tcx>,