diff --git a/src/librustc_codegen_llvm/base.rs b/src/librustc_codegen_llvm/base.rs
index cb44a56d07516..d3b524c1a1e70 100644
--- a/src/librustc_codegen_llvm/base.rs
+++ b/src/librustc_codegen_llvm/base.rs
@@ -13,7 +13,7 @@
//! but one `llvm::Type` corresponds to many `Ty`s; for instance, `tup(int, int,
//! int)` and `rec(x=int, y=int, z=int)` will have the same `llvm::Type`.
-use super::{LlvmCodegenBackend, ModuleLlvm};
+use super::ModuleLlvm;
use crate::builder::Builder;
use crate::common;
@@ -29,7 +29,6 @@ use rustc::middle::exported_symbols;
use rustc::mir::mono::{Linkage, Visibility};
use rustc::session::config::DebugInfo;
use rustc::ty::TyCtxt;
-use rustc_codegen_ssa::back::write::submit_codegened_module_to_llvm;
use rustc_codegen_ssa::base::maybe_create_entry_wrapper;
use rustc_codegen_ssa::mono_item::MonoItemExt;
use rustc_codegen_ssa::traits::*;
@@ -100,8 +99,7 @@ pub fn iter_globals(llmod: &'ll llvm::Module) -> ValueIter<'ll> {
pub fn compile_codegen_unit(
tcx: TyCtxt<'tcx>,
cgu_name: Symbol,
- tx_to_llvm_workers: &std::sync::mpsc::Sender<Box<dyn std::any::Any + Send>>,
-) {
+) -> (ModuleCodegen<ModuleLlvm>, u64) {
let prof_timer = tcx.prof.generic_activity("codegen_module");
let start_time = Instant::now();
@@ -115,8 +113,6 @@ pub fn compile_codegen_unit(
// the time we needed for codegenning it.
let cost = time_to_codegen.as_secs() * 1_000_000_000 + time_to_codegen.subsec_nanos() as u64;
- submit_codegened_module_to_llvm(&LlvmCodegenBackend(()), tx_to_llvm_workers, module, cost);
-
fn module_codegen(tcx: TyCtxt<'_>, cgu_name: Symbol) -> ModuleCodegen<ModuleLlvm> {
let cgu = tcx.codegen_unit(cgu_name);
// Instantiate monomorphizations without filling out definitions yet...
@@ -164,6 +160,8 @@ pub fn compile_codegen_unit(
kind: ModuleKind::Regular,
}
}
+
+ (module, cost)
}
pub fn set_link_section(llval: &Value, attrs: &CodegenFnAttrs) {
diff --git a/src/librustc_codegen_llvm/lib.rs b/src/librustc_codegen_llvm/lib.rs
index 35c71a6675683..a6168128c4d44 100644
--- a/src/librustc_codegen_llvm/lib.rs
+++ b/src/librustc_codegen_llvm/lib.rs
@@ -19,6 +19,7 @@
#![feature(link_args)]
#![feature(static_nobundle)]
#![feature(trusted_len)]
+#![recursion_limit = "256"]
use back::write::{create_informational_target_machine, create_target_machine};
use rustc_span::symbol::Symbol;
@@ -108,9 +109,8 @@ impl ExtraBackendMethods for LlvmCodegenBackend {
&self,
tcx: TyCtxt<'_>,
cgu_name: Symbol,
- tx: &std::sync::mpsc::Sender<Box<dyn Any + Send>>,
- ) {
- base::compile_codegen_unit(tcx, cgu_name, tx);
+ ) -> (ModuleCodegen<ModuleLlvm>, u64) {
+ base::compile_codegen_unit(tcx, cgu_name)
}
fn target_machine_factory(
&self,
diff --git a/src/librustc_codegen_ssa/base.rs b/src/librustc_codegen_ssa/base.rs
index c838109072775..3e39fa7c8f36d 100644
--- a/src/librustc_codegen_ssa/base.rs
+++ b/src/librustc_codegen_ssa/base.rs
@@ -14,8 +14,8 @@
//! int)` and `rec(x=int, y=int, z=int)` will have the same `llvm::Type`.
use crate::back::write::{
- start_async_codegen, submit_post_lto_module_to_llvm, submit_pre_lto_module_to_llvm,
- OngoingCodegen,
+ start_async_codegen, submit_codegened_module_to_llvm, submit_post_lto_module_to_llvm,
+ submit_pre_lto_module_to_llvm, OngoingCodegen,
};
use crate::common::{IntPredicate, RealPredicate, TypeKind};
use crate::meth;
@@ -40,6 +40,7 @@ use rustc::ty::{self, Instance, Ty, TyCtxt};
use rustc_codegen_utils::{check_for_rustc_errors_attr, symbol_names_test};
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::profiling::print_time_passes_entry;
+use rustc_data_structures::sync::{par_iter, Lock, ParallelIterator};
use rustc_hir as hir;
use rustc_hir::def_id::{DefId, LOCAL_CRATE};
use rustc_index::vec::Idx;
@@ -606,20 +607,83 @@ pub fn codegen_crate<B: ExtraBackendMethods>(
codegen_units
};
- let mut total_codegen_time = Duration::new(0, 0);
+ let total_codegen_time = Lock::new(Duration::new(0, 0));
- for cgu in codegen_units.into_iter() {
+ // The non-parallel compiler can only translate codegen units to LLVM IR
+ // on a single thread, leading to a staircase effect where the N LLVM
+ // threads have to wait on the single codegen threads to generate work
+ // for them. The parallel compiler does not have this restriction, so
+ // we can pre-load the LLVM queue in parallel before handing off
+ // coordination to the OnGoingCodegen scheduler.
+ //
+ // This likely is a temporary measure. Once we don't have to support the
+ // non-parallel compiler anymore, we can compile CGUs end-to-end in
+ // parallel and get rid of the complicated scheduling logic.
+ let pre_compile_cgus = |cgu_reuse: &[CguReuse]| {
+ if cfg!(parallel_compiler) {
+ tcx.sess.time("compile_first_CGU_batch", || {
+ // Try to find one CGU to compile per thread.
+ let cgus: Vec<_> = cgu_reuse
+ .iter()
+ .enumerate()
+ .filter(|&(_, reuse)| reuse == &CguReuse::No)
+ .take(tcx.sess.threads())
+ .collect();
+
+ // Compile the found CGUs in parallel.
+ par_iter(cgus)
+ .map(|(i, _)| {
+ let start_time = Instant::now();
+ let module = backend.compile_codegen_unit(tcx, codegen_units[i].name());
+ let mut time = total_codegen_time.lock();
+ *time += start_time.elapsed();
+ (i, module)
+ })
+ .collect()
+ })
+ } else {
+ FxHashMap::default()
+ }
+ };
+
+ let mut cgu_reuse = Vec::new();
+ let mut pre_compiled_cgus: Option<FxHashMap<usize, _>> = None;
+
+ for (i, cgu) in codegen_units.iter().enumerate() {
ongoing_codegen.wait_for_signal_to_codegen_item();
ongoing_codegen.check_for_errors(tcx.sess);
- let cgu_reuse = determine_cgu_reuse(tcx, &cgu);
+ // Do some setup work in the first iteration
+ if pre_compiled_cgus.is_none() {
+ // Calculate the CGU reuse
+ cgu_reuse = tcx.sess.time("find_cgu_reuse", || {
+ codegen_units.iter().map(|cgu| determine_cgu_reuse(tcx, &cgu)).collect()
+ });
+ // Pre compile some CGUs
+ pre_compiled_cgus = Some(pre_compile_cgus(&cgu_reuse));
+ }
+
+ let cgu_reuse = cgu_reuse[i];
tcx.sess.cgu_reuse_tracker.set_actual_reuse(&cgu.name().as_str(), cgu_reuse);
match cgu_reuse {
CguReuse::No => {
- let start_time = Instant::now();
- backend.compile_codegen_unit(tcx, cgu.name(), &ongoing_codegen.coordinator_send);
- total_codegen_time += start_time.elapsed();
+ let (module, cost) =
+ if let Some(cgu) = pre_compiled_cgus.as_mut().unwrap().remove(&i) {
+ cgu
+ } else {
+ let start_time = Instant::now();
+ let module = backend.compile_codegen_unit(tcx, cgu.name());
+ let mut time = total_codegen_time.lock();
+ *time += start_time.elapsed();
+ module
+ };
+ submit_codegened_module_to_llvm(
+ &backend,
+ &ongoing_codegen.coordinator_send,
+ module,
+ cost,
+ );
false
}
CguReuse::PreLto => {
@@ -652,7 +716,11 @@ pub fn codegen_crate<B: ExtraBackendMethods>(
// Since the main thread is sometimes blocked during codegen, we keep track
// -Ztime-passes output manually.
- print_time_passes_entry(tcx.sess.time_passes(), "codegen_to_LLVM_IR", total_codegen_time);
+ print_time_passes_entry(
+ tcx.sess.time_passes(),
+ "codegen_to_LLVM_IR",
+ total_codegen_time.into_inner(),
+ );
::rustc_incremental::assert_module_sources::assert_module_sources(tcx);
diff --git a/src/librustc_codegen_ssa/traits/backend.rs b/src/librustc_codegen_ssa/traits/backend.rs
index e0d0a2f32f331..bc3a75250bf70 100644
--- a/src/librustc_codegen_ssa/traits/backend.rs
+++ b/src/librustc_codegen_ssa/traits/backend.rs
@@ -1,5 +1,6 @@
use super::write::WriteBackendMethods;
use super::CodegenObject;
+use crate::ModuleCodegen;
use rustc::middle::cstore::EncodedMetadata;
use rustc::session::{config, Session};
@@ -10,7 +11,6 @@ use rustc_codegen_utils::codegen_backend::CodegenBackend;
use rustc_span::symbol::Symbol;
use syntax::expand::allocator::AllocatorKind;
-use std::sync::mpsc;
use std::sync::Arc;
pub trait BackendTypes {
@@ -34,7 +34,7 @@ impl<'tcx, T> Backend<'tcx> for T where
{
}
-pub trait ExtraBackendMethods: CodegenBackend + WriteBackendMethods + Sized + Send {
+pub trait ExtraBackendMethods: CodegenBackend + WriteBackendMethods + Sized + Send + Sync {
fn new_metadata(&self, sess: TyCtxt<'_>, mod_name: &str) -> Self::Module;
fn write_compressed_metadata<'tcx>(
&self,
@@ -48,12 +48,13 @@ pub trait ExtraBackendMethods: CodegenBackend + WriteBackendMethods + Sized + Se
mods: &mut Self::Module,
kind: AllocatorKind,
);
+ /// This generates the codegen unit and returns it along with
+ /// a `u64` giving an estimate of the unit's processing cost.
fn compile_codegen_unit(
&self,
tcx: TyCtxt<'_>,
cgu_name: Symbol,
- tx_to_llvm_workers: &mpsc::Sender<Box<dyn std::any::Any + Send>>,
- );
+ ) -> (ModuleCodegen<Self::Module>, u64);
// If find_features is true this won't access `sess.crate_types` by assuming
// that `is_pie_binary` is false. When we discover LLVM target features
// `sess.crate_types` is uninitialized so we cannot access it.