Move some code from Compiler::enter to GlobalCtxt::finish

compiler/rustc_middle/messages.ftl

@@ -73,6 +73,9 @@ middle_drop_check_overflow =
 
 middle_erroneous_constant = erroneous constant encountered
 
+middle_failed_writing_file =
+    failed to write file {$path}: {$error}"
+
 middle_layout_references_error =
     the type has an unknown layout
 

compiler/rustc_middle/src/error.rs

@@ -1,5 +1,5 @@
-use std::fmt;
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
+use std::{fmt, io};
 
 use rustc_errors::codes::*;
 use rustc_errors::{DiagArgName, DiagArgValue, DiagMessage};
@@ -18,6 +18,13 @@ pub struct DropCheckOverflow<'tcx> {
     pub overflow_ty: Ty<'tcx>,
 }
 
+#[derive(Diagnostic)]
+#[diag(middle_failed_writing_file)]
+pub struct FailedWritingFile<'a> {
+    pub path: &'a Path,
+    pub error: io::Error,
+}
+
 #[derive(Diagnostic)]
 #[diag(middle_opaque_hidden_type_mismatch)]
 pub struct OpaqueHiddenTypeMismatch<'tcx> {

compiler/rustc_middle/src/hooks/mod.rs

@@ -108,6 +108,19 @@ declare_hooks! {
     /// Returns `true` if we should codegen an instance in the local crate, or returns `false` if we
     /// can just link to the upstream crate and therefore don't need a mono item.
     hook should_codegen_locally(instance: crate::ty::Instance<'tcx>) -> bool;
+
+    hook alloc_self_profile_query_strings() -> ();
+
+    /// Saves and writes the DepGraph to the file system.
+    ///
+    /// This function saves both the dep-graph and the query result cache,
+    /// and drops the result cache.
+    ///
+    /// This function should only run after all queries have completed.
+    /// Trying to execute a query afterwards would attempt to read the result cache we just dropped.
+    hook save_dep_graph() -> ();
+
+    hook query_key_hash_verify_all() -> ();
 }
 
 #[cold]

compiler/rustc_middle/src/ty/context.rs

@@ -1365,8 +1365,17 @@ impl<'tcx> GlobalCtxt<'tcx> {
         tls::enter_context(&icx, || f(icx.tcx))
     }
 
-    pub fn finish(&self) -> FileEncodeResult {
-        self.dep_graph.finish_encoding()
+    pub fn finish(&'tcx self) {
+        // We assume that no queries are run past here. If there are new queries
+        // after this point, they'll show up as "<unknown>" in self-profiling data.
+        self.enter(|tcx| tcx.alloc_self_profile_query_strings());
+
+        self.enter(|tcx| tcx.save_dep_graph());
+        self.enter(|tcx| tcx.query_key_hash_verify_all());
+
+        if let Err((path, error)) = self.dep_graph.finish_encoding() {
+            self.sess.dcx().emit_fatal(crate::error::FailedWritingFile { path: &path, error });
+        }
     }
 }