Rollup merge of rust-lang#137410 - saethlin:stable-dep-tracking-hash, r=workingjubilee

Use StableHasher + Hash64 for dep_tracking_hash

This is similar to rust-lang#137095. We currently have a +/- 1 byte jitter in the size of dep graphs reported on perf.rust-lang.org. I think this fixes that jitter.

When I introduced `Hash64`, I wired it through most of the compiler by making it an output of `StableHasher::finalize` then fixing the compile errors. I missed this case because the `u64` hash in this function is being produced by `DefaultHasher` instead. That seems pretty sketchy because the code seems confident that the hash needs to be stable, and we have a mechanism for stable hashing that we weren't using here.

Author: matthiaskrgr

Cargo.lock

@@ -3779,6 +3779,7 @@ dependencies = [
  "rustc_fluent_macro",
  "rustc_fs_util",
  "rustc_graphviz",
+ "rustc_hashes",
  "rustc_hir",
  "rustc_macros",
  "rustc_middle",

compiler/rustc_incremental/Cargo.toml

@@ -12,6 +12,7 @@ rustc_errors = { path = "../rustc_errors" }
 rustc_fluent_macro = { path = "../rustc_fluent_macro" }
 rustc_fs_util = { path = "../rustc_fs_util" }
 rustc_graphviz = { path = "../rustc_graphviz" }
+rustc_hashes = { path = "../rustc_hashes" }
 rustc_hir = { path = "../rustc_hir" }
 rustc_macros = { path = "../rustc_macros" }
 rustc_middle = { path = "../rustc_middle" }

compiler/rustc_incremental/src/persist/load.rs

@@ -5,6 +5,7 @@ use std::sync::Arc;
 
 use rustc_data_structures::memmap::Mmap;
 use rustc_data_structures::unord::UnordMap;
+use rustc_hashes::Hash64;
 use rustc_middle::dep_graph::{DepGraph, DepsType, SerializedDepGraph, WorkProductMap};
 use rustc_middle::query::on_disk_cache::OnDiskCache;
 use rustc_serialize::Decodable;
@@ -154,7 +155,7 @@ fn load_dep_graph(sess: &Session) -> LoadResult<(Arc<SerializedDepGraph>, WorkPr
                 sess.dcx().emit_warn(errors::CorruptFile { path: &path });
                 return LoadResult::DataOutOfDate;
             };
-            let prev_commandline_args_hash = u64::decode(&mut decoder);
+            let prev_commandline_args_hash = Hash64::decode(&mut decoder);
 
             if prev_commandline_args_hash != expected_hash {
                 if sess.opts.unstable_opts.incremental_info {

compiler/rustc_session/src/config.rs

@@ -2928,12 +2928,13 @@ pub enum WasiExecModel {
 /// how the hash should be calculated when adding a new command-line argument.
 pub(crate) mod dep_tracking {
     use std::collections::BTreeMap;
-    use std::hash::{DefaultHasher, Hash};
+    use std::hash::Hash;
     use std::num::NonZero;
     use std::path::PathBuf;
 
     use rustc_abi::Align;
     use rustc_data_structures::fx::FxIndexMap;
+    use rustc_data_structures::stable_hasher::StableHasher;
     use rustc_errors::LanguageIdentifier;
     use rustc_feature::UnstableFeatures;
     use rustc_hashes::Hash64;
@@ -2960,7 +2961,7 @@ pub(crate) mod dep_tracking {
     pub(crate) trait DepTrackingHash {
         fn hash(
             &self,
-            hasher: &mut DefaultHasher,
+            hasher: &mut StableHasher,
             error_format: ErrorOutputType,
             for_crate_hash: bool,
         );
@@ -2969,7 +2970,7 @@ pub(crate) mod dep_tracking {
     macro_rules! impl_dep_tracking_hash_via_hash {
         ($($t:ty),+ $(,)?) => {$(
             impl DepTrackingHash for $t {
-                fn hash(&self, hasher: &mut DefaultHasher, _: ErrorOutputType, _for_crate_hash: bool) {
+                fn hash(&self, hasher: &mut StableHasher, _: ErrorOutputType, _for_crate_hash: bool) {
                     Hash::hash(self, hasher);
                 }
             }
@@ -2979,7 +2980,7 @@ pub(crate) mod dep_tracking {
     impl<T: DepTrackingHash> DepTrackingHash for Option<T> {
         fn hash(
             &self,
-            hasher: &mut DefaultHasher,
+            hasher: &mut StableHasher,
             error_format: ErrorOutputType,
             for_crate_hash: bool,
         ) {
@@ -3064,7 +3065,7 @@ pub(crate) mod dep_tracking {
     {
         fn hash(
             &self,
-            hasher: &mut DefaultHasher,
+            hasher: &mut StableHasher,
             error_format: ErrorOutputType,
             for_crate_hash: bool,
         ) {
@@ -3083,7 +3084,7 @@ pub(crate) mod dep_tracking {
     {
         fn hash(
             &self,
-            hasher: &mut DefaultHasher,
+            hasher: &mut StableHasher,
             error_format: ErrorOutputType,
             for_crate_hash: bool,
         ) {
@@ -3099,7 +3100,7 @@ pub(crate) mod dep_tracking {
     impl<T: DepTrackingHash> DepTrackingHash for Vec<T> {
         fn hash(
             &self,
-            hasher: &mut DefaultHasher,
+            hasher: &mut StableHasher,
             error_format: ErrorOutputType,
             for_crate_hash: bool,
         ) {
@@ -3114,7 +3115,7 @@ pub(crate) mod dep_tracking {
     impl<T: DepTrackingHash, V: DepTrackingHash> DepTrackingHash for FxIndexMap<T, V> {
         fn hash(
             &self,
-            hasher: &mut DefaultHasher,
+            hasher: &mut StableHasher,
             error_format: ErrorOutputType,
             for_crate_hash: bool,
         ) {
@@ -3129,7 +3130,7 @@ pub(crate) mod dep_tracking {
     impl DepTrackingHash for OutputTypes {
         fn hash(
             &self,
-            hasher: &mut DefaultHasher,
+            hasher: &mut StableHasher,
             error_format: ErrorOutputType,
             for_crate_hash: bool,
         ) {
@@ -3146,7 +3147,7 @@ pub(crate) mod dep_tracking {
     // This is a stable hash because BTreeMap is a sorted container
     pub(crate) fn stable_hash(
         sub_hashes: BTreeMap<&'static str, &dyn DepTrackingHash>,
-        hasher: &mut DefaultHasher,
+        hasher: &mut StableHasher,
         error_format: ErrorOutputType,
         for_crate_hash: bool,
     ) {

compiler/rustc_session/src/options.rs

@@ -1,12 +1,12 @@
 use std::collections::BTreeMap;
-use std::hash::{DefaultHasher, Hasher};
 use std::num::{IntErrorKind, NonZero};
 use std::path::PathBuf;
 use std::str;
 
 use rustc_abi::Align;
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::profiling::TimePassesFormat;
+use rustc_data_structures::stable_hasher::StableHasher;
 use rustc_errors::{ColorConfig, LanguageIdentifier, TerminalUrl};
 use rustc_feature::UnstableFeatures;
 use rustc_hashes::Hash64;
@@ -251,7 +251,7 @@ macro_rules! top_level_options {
         }
 
         impl Options {
-            pub fn dep_tracking_hash(&self, for_crate_hash: bool) -> u64 {
+            pub fn dep_tracking_hash(&self, for_crate_hash: bool) -> Hash64 {
                 let mut sub_hashes = BTreeMap::new();
                 $({
                     hash_opt!($opt,
@@ -260,7 +260,7 @@ macro_rules! top_level_options {
                                 for_crate_hash,
                                 [$dep_tracking_marker]);
                 })*
-                let mut hasher = DefaultHasher::new();
+                let mut hasher = StableHasher::new();
                 dep_tracking::stable_hash(sub_hashes,
                                           &mut hasher,
                                           self.error_format,
@@ -545,7 +545,7 @@ macro_rules! options {
             build_options(early_dcx, matches, target_modifiers, $stat, $prefix, $outputname)
         }
 
-        fn dep_tracking_hash(&self, for_crate_hash: bool, error_format: ErrorOutputType) -> u64 {
+        fn dep_tracking_hash(&self, for_crate_hash: bool, error_format: ErrorOutputType) -> Hash64 {
             let mut sub_hashes = BTreeMap::new();
             $({
                 hash_opt!($opt,
@@ -554,7 +554,7 @@ macro_rules! options {
                             for_crate_hash,
                             [$dep_tracking_marker]);
             })*
-            let mut hasher = DefaultHasher::new();
+            let mut hasher = StableHasher::new();
             dep_tracking::stable_hash(sub_hashes,
                                         &mut hasher,
                                         error_format,