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rustc_codegen_ssa: use wall time for codegen_to_LLVM_IR time-passes entry #81369

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Jan 26, 2021
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rustc_codegen_ssa: use wall time for codegen_to_LLVM_IR time-passes entry #81369

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31 changes: 14 additions & 17 deletions compiler/rustc_codegen_ssa/src/base.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,7 @@ use crate::{CachedModuleCodegen, CrateInfo, MemFlags, ModuleCodegen, ModuleKind}
use rustc_attr as attr;
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_data_structures::sync::{par_iter, ParallelIterator};
use rustc_hir as hir;
use rustc_hir::def_id::{LocalDefId, LOCAL_CRATE};
use rustc_hir::lang_items::LangItem;
Expand Down Expand Up @@ -554,8 +554,6 @@ pub fn codegen_crate<B: ExtraBackendMethods>(
codegen_units
};

let total_codegen_time = Lock::new(Duration::new(0, 0));

// 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
Expand All @@ -578,23 +576,25 @@ pub fn codegen_crate<B: ExtraBackendMethods>(
.collect();

// Compile the found CGUs in parallel.
par_iter(cgus)
let start_time = Instant::now();

let pre_compiled_cgus = 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()
.collect();

(pre_compiled_cgus, start_time.elapsed())
})
} else {
FxHashMap::default()
(FxHashMap::default(), Duration::new(0, 0))
}
};

let mut cgu_reuse = Vec::new();
let mut pre_compiled_cgus: Option<FxHashMap<usize, _>> = None;
let mut total_codegen_time = Duration::new(0, 0);

for (i, cgu) in codegen_units.iter().enumerate() {
ongoing_codegen.wait_for_signal_to_codegen_item();
Expand All @@ -607,7 +607,9 @@ pub fn codegen_crate<B: ExtraBackendMethods>(
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 (compiled_cgus, codegen_time) = pre_compile_cgus(&cgu_reuse);
pre_compiled_cgus = Some(compiled_cgus);
total_codegen_time += codegen_time;
}

let cgu_reuse = cgu_reuse[i];
Expand All @@ -621,8 +623,7 @@ pub fn codegen_crate<B: ExtraBackendMethods>(
} 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();
total_codegen_time += start_time.elapsed();
module
};
submit_codegened_module_to_llvm(
Expand Down Expand Up @@ -663,11 +664,7 @@ 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.into_inner(),
);
print_time_passes_entry(tcx.sess.time_passes(), "codegen_to_LLVM_IR", total_codegen_time);

ongoing_codegen.check_for_errors(tcx.sess);

Expand Down