From 01bcddbdc4b52e98807639d4c00129cd7ff36ce4 Mon Sep 17 00:00:00 2001
From: lcnr <rust@lcnr.de>
Date: Fri, 17 Sep 2021 09:13:16 +0200
Subject: [PATCH] `crates` is already deterministic

---
 .../rustc_metadata/src/dependency_format.rs   | 11 ++--
 .../src/rmeta/decoder/cstore_impl.rs          | 54 +++++++------------
 compiler/rustc_metadata/src/rmeta/encoder.rs  |  7 ++-
 3 files changed, 29 insertions(+), 43 deletions(-)

diff --git a/compiler/rustc_metadata/src/dependency_format.rs b/compiler/rustc_metadata/src/dependency_format.rs
index b8d22560618..cd368b8c56d 100644
--- a/compiler/rustc_metadata/src/dependency_format.rs
+++ b/compiler/rustc_metadata/src/dependency_format.rs
@@ -277,7 +277,7 @@ fn attempt_static(tcx: TyCtxt<'_>) -> Option<DependencyList> {
     let all_crates_available_as_rlib = tcx
         .crates(())
         .iter()
-        .cloned()
+        .copied()
         .filter_map(|cnum| {
             if tcx.dep_kind(cnum).macros_only() {
                 return None;
@@ -291,10 +291,11 @@ fn attempt_static(tcx: TyCtxt<'_>) -> Option<DependencyList> {
 
     // All crates are available in an rlib format, so we're just going to link
     // everything in explicitly so long as it's actually required.
-    let last_crate = tcx.crates(()).len();
-    let mut ret = (1..last_crate + 1)
-        .map(|cnum| {
-            if tcx.dep_kind(CrateNum::new(cnum)) == CrateDepKind::Explicit {
+    let mut ret = tcx
+        .crates(())
+        .iter()
+        .map(|&cnum| {
+            if tcx.dep_kind(cnum) == CrateDepKind::Explicit {
                 Linkage::Static
             } else {
                 Linkage::NotLinked
diff --git a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
index 70952d388d5..7be0e32ef38 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
@@ -304,17 +304,7 @@ pub fn provide(providers: &mut Providers) {
             // traversal, but not globally minimal across all crates.
             let bfs_queue = &mut VecDeque::new();
 
-            // Preferring shortest paths alone does not guarantee a
-            // deterministic result; so sort by crate num to avoid
-            // hashtable iteration non-determinism. This only makes
-            // things as deterministic as crate-nums assignment is,
-            // which is to say, its not deterministic in general. But
-            // we believe that libstd is consistently assigned crate
-            // num 1, so it should be enough to resolve #46112.
-            let mut crates: Vec<CrateNum> = (*tcx.crates(())).to_owned();
-            crates.sort();
-
-            for &cnum in crates.iter() {
+            for &cnum in tcx.crates(()) {
                 // Ignore crates without a corresponding local `extern crate` item.
                 if tcx.missing_extern_crate_item(cnum) {
                     continue;
@@ -323,35 +313,31 @@ pub fn provide(providers: &mut Providers) {
                 bfs_queue.push_back(DefId { krate: cnum, index: CRATE_DEF_INDEX });
             }
 
-            // (restrict scope of mutable-borrow of `visible_parent_map`)
-            {
-                let visible_parent_map = &mut visible_parent_map;
-                let mut add_child = |bfs_queue: &mut VecDeque<_>, child: &Export, parent: DefId| {
-                    if child.vis != ty::Visibility::Public {
-                        return;
-                    }
+            let mut add_child = |bfs_queue: &mut VecDeque<_>, child: &Export, parent: DefId| {
+                if child.vis != ty::Visibility::Public {
+                    return;
+                }
 
-                    if let Some(child) = child.res.opt_def_id() {
-                        match visible_parent_map.entry(child) {
-                            Entry::Occupied(mut entry) => {
-                                // If `child` is defined in crate `cnum`, ensure
-                                // that it is mapped to a parent in `cnum`.
-                                if child.is_local() && entry.get().is_local() {
-                                    entry.insert(parent);
-                                }
-                            }
-                            Entry::Vacant(entry) => {
+                if let Some(child) = child.res.opt_def_id() {
+                    match visible_parent_map.entry(child) {
+                        Entry::Occupied(mut entry) => {
+                            // If `child` is defined in crate `cnum`, ensure
+                            // that it is mapped to a parent in `cnum`.
+                            if child.is_local() && entry.get().is_local() {
                                 entry.insert(parent);
-                                bfs_queue.push_back(child);
                             }
                         }
+                        Entry::Vacant(entry) => {
+                            entry.insert(parent);
+                            bfs_queue.push_back(child);
+                        }
                     }
-                };
+                }
+            };
 
-                while let Some(def) = bfs_queue.pop_front() {
-                    for child in tcx.item_children(def).iter() {
-                        add_child(bfs_queue, child, def);
-                    }
+            while let Some(def) = bfs_queue.pop_front() {
+                for child in tcx.item_children(def).iter() {
+                    add_child(bfs_queue, child, def);
                 }
             }
 
diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index a50c4549d3d..8509aa00bc0 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -1708,9 +1708,10 @@ impl EncodeContext<'a, 'tcx> {
 
     fn encode_crate_deps(&mut self) -> Lazy<[CrateDep]> {
         empty_proc_macro!(self);
-        let crates = self.tcx.crates(());
 
-        let mut deps = crates
+        let deps = self
+            .tcx
+            .crates(())
             .iter()
             .map(|&cnum| {
                 let dep = CrateDep {
@@ -1724,8 +1725,6 @@ impl EncodeContext<'a, 'tcx> {
             })
             .collect::<Vec<_>>();
 
-        deps.sort_by_key(|&(cnum, _)| cnum);
-
         {
             // Sanity-check the crate numbers
             let mut expected_cnum = 1;