Make hash_result an Option.

compiler/rustc_codegen_cranelift/src/driver/aot.rs

@@ -224,7 +224,7 @@ pub(crate) fn run_aot(
                     tcx,
                     (backend_config.clone(), cgu.name()),
                     module_codegen,
-                    rustc_middle::dep_graph::hash_result,
+                    Some(rustc_middle::dep_graph::hash_result),
                 );
 
                 if let Some((id, product)) = work_product {

compiler/rustc_codegen_gcc/src/base.rs

@@ -59,7 +59,13 @@ pub fn compile_codegen_unit<'tcx>(tcx: TyCtxt<'tcx>, cgu_name: Symbol) -> (Modul
     let start_time = Instant::now();
 
     let dep_node = tcx.codegen_unit(cgu_name).codegen_dep_node(tcx);
-    let (module, _) = tcx.dep_graph.with_task(dep_node, tcx, cgu_name, module_codegen, dep_graph::hash_result);
+    let (module, _) = tcx.dep_graph.with_task(
+        dep_node,
+        tcx,
+        cgu_name,
+        module_codegen,
+        Some(dep_graph::hash_result),
+    );
     let time_to_codegen = start_time.elapsed();
     drop(prof_timer);
 

compiler/rustc_codegen_llvm/src/base.rs

@@ -113,8 +113,13 @@ pub fn compile_codegen_unit(
     let start_time = Instant::now();
 
     let dep_node = tcx.codegen_unit(cgu_name).codegen_dep_node(tcx);
-    let (module, _) =
-        tcx.dep_graph.with_task(dep_node, tcx, cgu_name, module_codegen, dep_graph::hash_result);
+    let (module, _) = tcx.dep_graph.with_task(
+        dep_node,
+        tcx,
+        cgu_name,
+        module_codegen,
+        Some(dep_graph::hash_result),
+    );
     let time_to_codegen = start_time.elapsed();
 
     // We assume that the cost to run LLVM on a CGU is proportional to

compiler/rustc_query_impl/src/plumbing.rs

@@ -291,14 +291,14 @@ pub struct QueryStruct {
 }
 
 macro_rules! hash_result {
-    ([][$hcx:expr, $result:expr]) => {{
-        dep_graph::hash_result($hcx, &$result)
+    ([]) => {{
+        Some(dep_graph::hash_result)
     }};
-    ([(no_hash) $($rest:tt)*][$hcx:expr, $result:expr]) => {{
+    ([(no_hash) $($rest:tt)*]) => {{
         None
     }};
-    ([$other:tt $($modifiers:tt)*][$($args:tt)*]) => {
-        hash_result!([$($modifiers)*][$($args)*])
+    ([$other:tt $($modifiers:tt)*]) => {
+        hash_result!([$($modifiers)*])
     };
 }
 
@@ -378,6 +378,7 @@ impl<$tcx> QueryAccessors<QueryCtxt<$tcx>> for queries::$name<$tcx> {
             const ANON: bool = is_anon!([$($modifiers)*]);
             const EVAL_ALWAYS: bool = is_eval_always!([$($modifiers)*]);
             const DEP_KIND: dep_graph::DepKind = dep_graph::DepKind::$name;
+            const HASH_RESULT: Option<fn(&mut StableHashingContext<'_>, &Self::Value) -> Fingerprint> = hash_result!([$($modifiers)*]);
 
             type Cache = query_storage::$name<$tcx>;
 
@@ -406,13 +407,6 @@ fn compute_fn(tcx: QueryCtxt<'tcx>, key: &Self::Key) ->
                 }
             }
 
-            fn hash_result(
-                _hcx: &mut StableHashingContext<'_>,
-                _result: &Self::Value
-            ) -> Option<Fingerprint> {
-                hash_result!([$($modifiers)*][_hcx, _result])
-            }
-
             fn handle_cycle_error(
                 tcx: QueryCtxt<'tcx>,
                 mut error: DiagnosticBuilder<'_>,

compiler/rustc_query_system/src/dep_graph/graph.rs

@@ -96,14 +96,13 @@ struct DepGraphData<K: DepKind> {
     dep_node_debug: Lock<FxHashMap<DepNode<K>, String>>,
 }
 
-pub fn hash_result<R>(hcx: &mut StableHashingContext<'_>, result: &R) -> Option<Fingerprint>
+pub fn hash_result<R>(hcx: &mut StableHashingContext<'_>, result: &R) -> Fingerprint
 where
     R: for<'a> HashStable<StableHashingContext<'a>>,
 {
     let mut stable_hasher = StableHasher::new();
     result.hash_stable(hcx, &mut stable_hasher);
-
-    Some(stable_hasher.finish())
+    stable_hasher.finish()
 }
 
 impl<K: DepKind> DepGraph<K> {
@@ -215,7 +214,7 @@ pub fn with_task<Ctxt: HasDepContext<DepKind = K>, A: Debug, R>(
         cx: Ctxt,
         arg: A,
         task: fn(Ctxt, A) -> R,
-        hash_result: fn(&mut StableHashingContext<'_>, &R) -> Option<Fingerprint>,
+        hash_result: Option<fn(&mut StableHashingContext<'_>, &R) -> Fingerprint>,
     ) -> (R, DepNodeIndex) {
         if self.is_fully_enabled() {
             self.with_task_impl(key, cx, arg, task, hash_result)
@@ -234,7 +233,7 @@ fn with_task_impl<Ctxt: HasDepContext<DepKind = K>, A: Debug, R>(
         cx: Ctxt,
         arg: A,
         task: fn(Ctxt, A) -> R,
-        hash_result: fn(&mut StableHashingContext<'_>, &R) -> Option<Fingerprint>,
+        hash_result: Option<fn(&mut StableHashingContext<'_>, &R) -> Fingerprint>,
     ) -> (R, DepNodeIndex) {
         // This function is only called when the graph is enabled.
         let data = self.data.as_ref().unwrap();
@@ -268,9 +267,11 @@ fn with_task_impl<Ctxt: HasDepContext<DepKind = K>, A: Debug, R>(
         let edges = task_deps.map_or_else(|| smallvec![], |lock| lock.into_inner().reads);
 
         let dcx = cx.dep_context();
-        let mut hcx = dcx.create_stable_hashing_context();
         let hashing_timer = dcx.profiler().incr_result_hashing();
-        let current_fingerprint = hash_result(&mut hcx, &result);
+        let current_fingerprint = hash_result.map(|f| {
+            let mut hcx = dcx.create_stable_hashing_context();
+            f(&mut hcx, &result)
+        });
 
         let print_status = cfg!(debug_assertions) && dcx.sess().opts.debugging_opts.dep_tasks;
 

compiler/rustc_query_system/src/query/config.rs

@@ -24,7 +24,7 @@ pub(crate) struct QueryVtable<CTX: QueryContext, K, V> {
     pub dep_kind: CTX::DepKind,
     pub eval_always: bool,
 
-    pub hash_result: fn(&mut StableHashingContext<'_>, &V) -> Option<Fingerprint>,
+    pub hash_result: Option<fn(&mut StableHashingContext<'_>, &V) -> Fingerprint>,
     pub handle_cycle_error: fn(CTX, DiagnosticBuilder<'_>) -> V,
     pub cache_on_disk: fn(CTX, &K, Option<&V>) -> bool,
     pub try_load_from_disk: fn(CTX, SerializedDepNodeIndex) -> Option<V>,
@@ -38,14 +38,6 @@ pub(crate) fn to_dep_node(&self, tcx: CTX::DepContext, key: &K) -> DepNode<CTX::
         DepNode::construct(tcx, self.dep_kind, key)
     }
 
-    pub(crate) fn hash_result(
-        &self,
-        hcx: &mut StableHashingContext<'_>,
-        value: &V,
-    ) -> Option<Fingerprint> {
-        (self.hash_result)(hcx, value)
-    }
-
     pub(crate) fn cache_on_disk(&self, tcx: CTX, key: &K, value: Option<&V>) -> bool {
         (self.cache_on_disk)(tcx, key, value)
     }
@@ -59,6 +51,9 @@ pub trait QueryAccessors<CTX: QueryContext>: QueryConfig {
     const ANON: bool;
     const EVAL_ALWAYS: bool;
     const DEP_KIND: CTX::DepKind;
+    const HASH_RESULT: Option<
+        fn(hcx: &mut StableHashingContext<'_>, result: &Self::Value) -> Fingerprint,
+    >;
 
     type Cache: QueryCache<Key = Self::Key, Stored = Self::Stored, Value = Self::Value>;
 
@@ -75,9 +70,6 @@ fn query_cache<'a>(tcx: CTX) -> &'a QueryCacheStore<Self::Cache>
     // Don't use this method to compute query results, instead use the methods on TyCtxt
     fn compute_fn(tcx: CTX, key: &Self::Key) -> fn(CTX::DepContext, Self::Key) -> Self::Value;
 
-    fn hash_result(hcx: &mut StableHashingContext<'_>, result: &Self::Value)
-    -> Option<Fingerprint>;
-
     fn handle_cycle_error(tcx: CTX, diag: DiagnosticBuilder<'_>) -> Self::Value;
 }
 
@@ -107,7 +99,7 @@ impl<CTX, Q> QueryVtableExt<CTX, Q::Key, Q::Value> for Q
         anon: Q::ANON,
         dep_kind: Q::DEP_KIND,
         eval_always: Q::EVAL_ALWAYS,
-        hash_result: Q::hash_result,
+        hash_result: Q::HASH_RESULT,
         handle_cycle_error: Q::handle_cycle_error,
         cache_on_disk: Q::cache_on_disk,
         try_load_from_disk: Q::try_load_from_disk,

compiler/rustc_query_system/src/query/plumbing.rs

@@ -577,12 +577,12 @@ fn incremental_verify_ich<CTX, K, V: Debug>(
     );
 
     debug!("BEGIN verify_ich({:?})", dep_node);
-    let mut hcx = tcx.create_stable_hashing_context();
-
-    let new_hash = query.hash_result(&mut hcx, result).unwrap_or(Fingerprint::ZERO);
-    debug!("END verify_ich({:?})", dep_node);
-
+    let new_hash = query.hash_result.map_or(Fingerprint::ZERO, |f| {
+        let mut hcx = tcx.create_stable_hashing_context();
+        f(&mut hcx, result)
+    });
     let old_hash = tcx.dep_graph().prev_fingerprint_of(dep_node);
+    debug!("END verify_ich({:?})", dep_node);
 
     if Some(new_hash) != old_hash {
         let run_cmd = if let Some(crate_name) = &tcx.sess().opts.crate_name {