Remove the use of Rayon iterators

Cargo.lock

@@ -3154,17 +3154,6 @@ dependencies = [
  "tikv-jemalloc-sys",
 ]
 
-[[package]]
-name = "rustc-rayon"
-version = "0.5.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2cd9fb077db982d7ceb42a90471e5a69a990b58f71e06f0d8340bb2cf35eb751"
-dependencies = [
- "either",
- "indexmap",
- "rustc-rayon-core",
-]
-
 [[package]]
 name = "rustc-rayon-core"
 version = "0.5.0"
@@ -3536,7 +3525,7 @@ dependencies = [
  "parking_lot",
  "portable-atomic",
  "rustc-hash 2.1.1",
- "rustc-rayon",
+ "rustc-rayon-core",
  "rustc-stable-hash",
  "rustc_arena",
  "rustc_graphviz",
@@ -3882,7 +3871,6 @@ dependencies = [
 name = "rustc_interface"
 version = "0.0.0"
 dependencies = [
- "rustc-rayon",
  "rustc-rayon-core",
  "rustc_abi",
  "rustc_ast",

compiler/rustc_codegen_cranelift/src/driver/aot.rs

@@ -728,26 +728,27 @@ pub(crate) fn run_aot(
 
     let concurrency_limiter = IntoDynSyncSend(ConcurrencyLimiter::new(todo_cgus.len()));
 
-    let modules = tcx.sess.time("codegen mono items", || {
-        let mut modules: Vec<_> = par_map(todo_cgus, |(_, cgu)| {
-            let dep_node = cgu.codegen_dep_node(tcx);
-            tcx.dep_graph
-                .with_task(
+    let modules: Vec<_> =
+        tcx.sess.time("codegen mono items", || {
+            let modules: Vec<_> = par_map(todo_cgus, |(_, cgu)| {
+                let dep_node = cgu.codegen_dep_node(tcx);
+                let (module, _) = tcx.dep_graph.with_task(
                     dep_node,
                     tcx,
                     (global_asm_config.clone(), cgu.name(), concurrency_limiter.acquire(tcx.dcx())),
                     module_codegen,
                     Some(rustc_middle::dep_graph::hash_result),
-                )
-                .0
-        });
-        modules.extend(
-            done_cgus
+                );
+                IntoDynSyncSend(module)
+            });
+            modules
                 .into_iter()
-                .map(|(_, cgu)| OngoingModuleCodegen::Sync(reuse_workproduct_for_cgu(tcx, cgu))),
-        );
-        modules
-    });
+                .map(|module| module.0)
+                .chain(done_cgus.into_iter().map(|(_, cgu)| {
+                    OngoingModuleCodegen::Sync(reuse_workproduct_for_cgu(tcx, cgu))
+                }))
+                .collect()
+        });
 
     let allocator_module = emit_allocator_module(tcx);
 

compiler/rustc_codegen_ssa/src/base.rs

@@ -10,7 +10,7 @@ use rustc_ast::expand::allocator::{ALLOCATOR_METHODS, AllocatorKind, global_fn_n
 use rustc_attr_parsing::OptimizeAttr;
 use rustc_data_structures::fx::{FxHashMap, FxIndexSet};
 use rustc_data_structures::profiling::{get_resident_set_size, print_time_passes_entry};
-use rustc_data_structures::sync::par_map;
+use rustc_data_structures::sync::{IntoDynSyncSend, par_map};
 use rustc_data_structures::unord::UnordMap;
 use rustc_hir::def_id::{DefId, LOCAL_CRATE};
 use rustc_hir::lang_items::LangItem;
@@ -757,7 +757,7 @@ pub fn codegen_crate<B: ExtraBackendMethods>(
 
             let pre_compiled_cgus = par_map(cgus, |(i, _)| {
                 let module = backend.compile_codegen_unit(tcx, codegen_units[i].name());
-                (i, module)
+                (i, IntoDynSyncSend(module))
             });
 
             total_codegen_time += start_time.elapsed();
@@ -777,7 +777,7 @@ pub fn codegen_crate<B: ExtraBackendMethods>(
         match cgu_reuse {
             CguReuse::No => {
                 let (module, cost) = if let Some(cgu) = pre_compiled_cgus.remove(&i) {
-                    cgu
+                    cgu.0
                 } else {
                     let start_time = Instant::now();
                     let module = backend.compile_codegen_unit(tcx, cgu.name());

compiler/rustc_data_structures/Cargo.toml

@@ -14,7 +14,7 @@ indexmap = "2.4.0"
 jobserver_crate = { version = "0.1.28", package = "jobserver" }
 measureme = "12.0.1"
 rustc-hash = "2.0.0"
-rustc-rayon = { version = "0.5.1", features = ["indexmap"] }
+rustc-rayon-core = { version = "0.5.0" }
 rustc-stable-hash = { version = "0.1.0", features = ["nightly"] }
 rustc_arena = { path = "../rustc_arena" }
 rustc_graphviz = { path = "../rustc_graphviz" }

compiler/rustc_data_structures/src/marker.rs

@@ -179,6 +179,12 @@ impl<T> FromDyn<T> {
         FromDyn(val)
     }
 
+    #[inline(always)]
+    pub fn derive<O>(&self, val: O) -> FromDyn<O> {
+        // We already did the check for `sync::is_dyn_thread_safe()` when creating `Self`
+        FromDyn(val)
+    }
+
     #[inline(always)]
     pub fn into_inner(self) -> T {
         self.0
@@ -200,6 +206,13 @@ impl<T> std::ops::Deref for FromDyn<T> {
     }
 }
 
+impl<T> std::ops::DerefMut for FromDyn<T> {
+    #[inline(always)]
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.0
+    }
+}
+
 // A wrapper to convert a struct that is already a `Send` or `Sync` into
 // an instance of `DynSend` and `DynSync`, since the compiler cannot infer
 // it automatically in some cases. (e.g. Box<dyn Send / Sync>)

compiler/rustc_data_structures/src/sync/parallel.rs

@@ -7,7 +7,6 @@ use std::any::Any;
 use std::panic::{AssertUnwindSafe, catch_unwind, resume_unwind};
 
 use parking_lot::Mutex;
-use rayon::iter::{FromParallelIterator, IntoParallelIterator, ParallelIterator};
 
 use crate::FatalErrorMarker;
 use crate::sync::{DynSend, DynSync, FromDyn, IntoDynSyncSend, mode};
@@ -97,11 +96,11 @@ macro_rules! parallel {
 // This function only works when `mode::is_dyn_thread_safe()`.
 pub fn scope<'scope, OP, R>(op: OP) -> R
 where
-    OP: FnOnce(&rayon::Scope<'scope>) -> R + DynSend,
+    OP: FnOnce(&rayon_core::Scope<'scope>) -> R + DynSend,
     R: DynSend,
 {
     let op = FromDyn::from(op);
-    rayon::scope(|s| FromDyn::from(op.into_inner()(s))).into_inner()
+    rayon_core::scope(|s| FromDyn::from(op.into_inner()(s))).into_inner()
 }
 
 #[inline]
@@ -114,7 +113,7 @@ where
         let oper_a = FromDyn::from(oper_a);
         let oper_b = FromDyn::from(oper_b);
         let (a, b) = parallel_guard(|guard| {
-            rayon::join(
+            rayon_core::join(
                 move || guard.run(move || FromDyn::from(oper_a.into_inner()())),
                 move || guard.run(move || FromDyn::from(oper_b.into_inner()())),
             )
@@ -125,56 +124,103 @@ where
     }
 }
 
-pub fn par_for_each_in<I, T: IntoIterator<Item = I> + IntoParallelIterator<Item = I>>(
+fn par_slice<I: DynSend>(
+    items: &mut [I],
+    guard: &ParallelGuard,
+    for_each: impl Fn(&mut I) + DynSync + DynSend,
+) {
+    struct State<'a, F> {
+        for_each: FromDyn<F>,
+        guard: &'a ParallelGuard,
+        group: usize,
+    }
+
+    fn par_rec<I: DynSend, F: Fn(&mut I) + DynSync + DynSend>(
+        items: &mut [I],
+        state: &State<'_, F>,
+    ) {
+        if items.len() <= state.group {
+            for item in items {
+                state.guard.run(|| (state.for_each)(item));
+            }
+        } else {
+            let (left, right) = items.split_at_mut(items.len() / 2);
+            let mut left = state.for_each.derive(left);
+            let mut right = state.for_each.derive(right);
+            rayon_core::join(move || par_rec(*left, state), move || par_rec(*right, state));
+        }
+    }
+
+    let state = State {
+        for_each: FromDyn::from(for_each),
+        guard,
+        group: std::cmp::max(items.len() / 128, 1),
+    };
+    par_rec(items, &state)
+}
+
+pub fn par_for_each_in<I: DynSend, T: IntoIterator<Item = I>>(
     t: T,
-    for_each: impl Fn(I) + DynSync + DynSend,
+    for_each: impl Fn(&I) + DynSync + DynSend,
 ) {
     parallel_guard(|guard| {
         if mode::is_dyn_thread_safe() {
-            let for_each = FromDyn::from(for_each);
-            t.into_par_iter().for_each(|i| {
-                guard.run(|| for_each(i));
-            });
+            let mut items: Vec<_> = t.into_iter().collect();
+            par_slice(&mut items, guard, |i| for_each(&*i))
         } else {
             t.into_iter().for_each(|i| {
-                guard.run(|| for_each(i));
+                guard.run(|| for_each(&i));
             });
         }
     });
 }
 
-pub fn try_par_for_each_in<
-    T: IntoIterator + IntoParallelIterator<Item = <T as IntoIterator>::Item>,
-    E: Send,
->(
+/// This runs `for_each` in parallel for each iterator item. If one or more of the
+/// `for_each` calls returns `Err`, the function will also return `Err`. The error returned
+/// will be non-deterministic, but this is expected to be used with `ErrorGuaranteed` which
+/// are all equivalent.
+pub fn try_par_for_each_in<T: IntoIterator, E: DynSend>(
     t: T,
-    for_each: impl Fn(<T as IntoIterator>::Item) -> Result<(), E> + DynSync + DynSend,
-) -> Result<(), E> {
+    for_each: impl Fn(&<T as IntoIterator>::Item) -> Result<(), E> + DynSync + DynSend,
+) -> Result<(), E>
+where
+    <T as IntoIterator>::Item: DynSend,
+{
     parallel_guard(|guard| {
         if mode::is_dyn_thread_safe() {
-            let for_each = FromDyn::from(for_each);
-            t.into_par_iter()
-                .filter_map(|i| guard.run(|| for_each(i)))
-                .reduce(|| Ok(()), Result::and)
+            let mut items: Vec<_> = t.into_iter().collect();
+
+            let error = Mutex::new(None);
+
+            par_slice(&mut items, guard, |i| {
+                if let Err(err) = for_each(&*i) {
+                    *error.lock() = Some(err);
+                }
+            });
+
+            if let Some(err) = error.into_inner() { Err(err) } else { Ok(()) }
         } else {
-            t.into_iter().filter_map(|i| guard.run(|| for_each(i))).fold(Ok(()), Result::and)
+            t.into_iter().filter_map(|i| guard.run(|| for_each(&i))).fold(Ok(()), Result::and)
         }
     })
 }
 
-pub fn par_map<
-    I,
-    T: IntoIterator<Item = I> + IntoParallelIterator<Item = I>,
-    R: std::marker::Send,
-    C: FromIterator<R> + FromParallelIterator<R>,
->(
+pub fn par_map<I: DynSend, T: IntoIterator<Item = I>, R: DynSend, C: FromIterator<R>>(
     t: T,
     map: impl Fn(I) -> R + DynSync + DynSend,
 ) -> C {
     parallel_guard(|guard| {
         if mode::is_dyn_thread_safe() {
             let map = FromDyn::from(map);
-            t.into_par_iter().filter_map(|i| guard.run(|| map(i))).collect()
+
+            let mut items: Vec<(Option<I>, Option<R>)> =
+                t.into_iter().map(|i| (Some(i), None)).collect();
+
+            par_slice(&mut items, guard, |i| {
+                i.1 = Some(map(i.0.take().unwrap()));
+            });
+
+            items.into_iter().filter_map(|i| i.1).collect()
         } else {
             t.into_iter().filter_map(|i| guard.run(|| map(i))).collect()
         }

compiler/rustc_interface/Cargo.toml

@@ -5,7 +5,6 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-rustc-rayon = { version = "0.5.0" }
 rustc-rayon-core = { version = "0.5.0" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_lowering = { path = "../rustc_ast_lowering" }

compiler/rustc_interface/src/util.rs

@@ -179,7 +179,7 @@ pub(crate) fn run_in_thread_pool_with_globals<F: FnOnce(CurrentGcx) -> R + Send,
     let current_gcx = FromDyn::from(CurrentGcx::new());
     let current_gcx2 = current_gcx.clone();
 
-    let builder = rayon::ThreadPoolBuilder::new()
+    let builder = rayon_core::ThreadPoolBuilder::new()
         .thread_name(|_| "rustc".to_string())
         .acquire_thread_handler(jobserver::acquire_thread)
         .release_thread_handler(jobserver::release_thread)
@@ -223,7 +223,7 @@ pub(crate) fn run_in_thread_pool_with_globals<F: FnOnce(CurrentGcx) -> R + Send,
             builder
                 .build_scoped(
                     // Initialize each new worker thread when created.
-                    move |thread: rayon::ThreadBuilder| {
+                    move |thread: rayon_core::ThreadBuilder| {
                         // Register the thread for use with the `WorkerLocal` type.
                         registry.register();
 
@@ -232,7 +232,9 @@ pub(crate) fn run_in_thread_pool_with_globals<F: FnOnce(CurrentGcx) -> R + Send,
                         })
                     },
                     // Run `f` on the first thread in the thread pool.
-                    move |pool: &rayon::ThreadPool| pool.install(|| f(current_gcx.into_inner())),
+                    move |pool: &rayon_core::ThreadPool| {
+                        pool.install(|| f(current_gcx.into_inner()))
+                    },
                 )
                 .unwrap()
         })

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -2192,7 +2192,7 @@ fn prefetch_mir(tcx: TyCtxt<'_>) {
     }
 
     let reachable_set = tcx.reachable_set(());
-    par_for_each_in(tcx.mir_keys(()), |&def_id| {
+    par_for_each_in(tcx.mir_keys(()), |&&def_id| {
         let (encode_const, encode_opt) = should_encode_mir(tcx, reachable_set, def_id);
 
         if encode_const {

compiler/rustc_middle/src/hir/map.rs

@@ -342,7 +342,7 @@ impl<'tcx> TyCtxt<'tcx> {
 
     #[inline]
     pub fn par_hir_body_owners(self, f: impl Fn(LocalDefId) + DynSend + DynSync) {
-        par_for_each_in(&self.hir_crate_items(()).body_owners[..], |&def_id| f(def_id));
+        par_for_each_in(&self.hir_crate_items(()).body_owners[..], |&&def_id| f(def_id));
     }
 
     pub fn hir_ty_param_owner(self, def_id: LocalDefId) -> LocalDefId {

compiler/rustc_middle/src/hir/mod.rs

@@ -83,35 +83,35 @@ impl ModuleItems {
         &self,
         f: impl Fn(ItemId) -> Result<(), ErrorGuaranteed> + DynSend + DynSync,
     ) -> Result<(), ErrorGuaranteed> {
-        try_par_for_each_in(&self.free_items[..], |&id| f(id))
+        try_par_for_each_in(&self.free_items[..], |&&id| f(id))
     }
 
     pub fn par_trait_items(
         &self,
         f: impl Fn(TraitItemId) -> Result<(), ErrorGuaranteed> + DynSend + DynSync,
     ) -> Result<(), ErrorGuaranteed> {
-        try_par_for_each_in(&self.trait_items[..], |&id| f(id))
+        try_par_for_each_in(&self.trait_items[..], |&&id| f(id))
     }
 
     pub fn par_impl_items(
         &self,
         f: impl Fn(ImplItemId) -> Result<(), ErrorGuaranteed> + DynSend + DynSync,
     ) -> Result<(), ErrorGuaranteed> {
-        try_par_for_each_in(&self.impl_items[..], |&id| f(id))
+        try_par_for_each_in(&self.impl_items[..], |&&id| f(id))
     }
 
     pub fn par_foreign_items(
         &self,
         f: impl Fn(ForeignItemId) -> Result<(), ErrorGuaranteed> + DynSend + DynSync,
     ) -> Result<(), ErrorGuaranteed> {
-        try_par_for_each_in(&self.foreign_items[..], |&id| f(id))
+        try_par_for_each_in(&self.foreign_items[..], |&&id| f(id))
     }
 
     pub fn par_opaques(
         &self,
         f: impl Fn(LocalDefId) -> Result<(), ErrorGuaranteed> + DynSend + DynSync,
     ) -> Result<(), ErrorGuaranteed> {
-        try_par_for_each_in(&self.opaques[..], |&id| f(id))
+        try_par_for_each_in(&self.opaques[..], |&&id| f(id))
     }
 }