Rollup merge of #69965 - mark-i-m:codegen-utils, r=eddyb

Refactorings to get rid of rustc_codegen_utils

r? @eddyb

cc #45276

After this, the only modules left in `rustc_codegen_utils` are
- `link`: a bunch of linking-related functions (many dealing with file names). These are mostly consumed by save analysis, rustc_driver, rustc_interface, and of course codegen. I assume they live here because we don't want a dependency of save analysis on codegen... Perhaps they can be moved to librustc?
- ~`symbol_names` and `symbol_names_test`: honestly it seems odd that `symbol_names_test` is not a submodule of `symbol_names`. It seems like these could honestly live in their own crate or move to librustc. Already name mangling is exported as the `symbol_name` query.~ (move it to its own crate)

I don't mind doing either of the above as part of this PR or a followup if you want.

src/librustc_codegen_ssa/back/link.rs

@@ -6,6 +6,7 @@ use rustc_hir::def_id::CrateNum;
 use rustc_session::config::{
     self, CFGuard, DebugInfo, OutputFilenames, OutputType, PrintRequest, Sanitizer,
 };
+use rustc_session::output::{check_file_is_writeable, invalid_output_for_target, out_filename};
 use rustc_session::search_paths::PathKind;
 /// For all the linkers we support, and information they might
 /// need out of the shared crate context before we get rid of it.
@@ -36,8 +37,6 @@ use std::path::{Path, PathBuf};
 use std::process::{ExitStatus, Output, Stdio};
 use std::str;
 
-pub use rustc_codegen_utils::link::*;
-
 pub fn remove(sess: &Session, path: &Path) {
     if let Err(e) = fs::remove_file(path) {
         sess.err(&format!("failed to remove {}: {}", path.display(), e));

src/librustc_codegen_ssa/back/symbol_export.rs

@@ -8,7 +8,6 @@ use rustc::ty::subst::{GenericArgKind, SubstsRef};
 use rustc::ty::Instance;
 use rustc::ty::{SymbolName, TyCtxt};
 use rustc_ast::expand::allocator::ALLOCATOR_METHODS;
-use rustc_codegen_utils::symbol_names;
 use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_hir as hir;
@@ -423,17 +422,21 @@ pub fn symbol_name_for_instance_in_crate<'tcx>(
     // This is something instantiated in an upstream crate, so we have to use
     // the slower (because uncached) version of computing the symbol name.
     match symbol {
-        ExportedSymbol::NonGeneric(def_id) => symbol_names::symbol_name_for_instance_in_crate(
-            tcx,
-            Instance::mono(tcx, def_id),
-            instantiating_crate,
-        ),
-        ExportedSymbol::Generic(def_id, substs) => symbol_names::symbol_name_for_instance_in_crate(
-            tcx,
-            Instance::new(def_id, substs),
-            instantiating_crate,
-        ),
-        ExportedSymbol::DropGlue(ty) => symbol_names::symbol_name_for_instance_in_crate(
+        ExportedSymbol::NonGeneric(def_id) => {
+            rustc_symbol_mangling::symbol_name_for_instance_in_crate(
+                tcx,
+                Instance::mono(tcx, def_id),
+                instantiating_crate,
+            )
+        }
+        ExportedSymbol::Generic(def_id, substs) => {
+            rustc_symbol_mangling::symbol_name_for_instance_in_crate(
+                tcx,
+                Instance::new(def_id, substs),
+                instantiating_crate,
+            )
+        }
+        ExportedSymbol::DropGlue(ty) => rustc_symbol_mangling::symbol_name_for_instance_in_crate(
             tcx,
             Instance::resolve_drop_in_place(tcx, ty),
             instantiating_crate,