use rustc::ty::{self, TyCtxt, InstanceDef};
use rustc::ty::item_path::characteristic_def_id_of_type;
use rustc::util::nodemap::{FxHashMap, FxHashSet};
-use std::collections::hash_map::Entry;
+use std::collections::hash_map::{HashMap, Entry};
use syntax::ast::NodeId;
use syntax::symbol::{Symbol, InternedString};
use rustc::mir::mono::MonoItem;
use monomorphize::item::{MonoItemExt, InstantiationMode};
+use core::usize;
pub use rustc::mir::mono::CodegenUnit;
// If the partitioning should produce a fixed count of codegen units, merge
// until that count is reached.
if let PartitioningStrategy::FixedUnitCount(count) = strategy {
- merge_codegen_units(&mut initial_partitioning, count, &tcx.crate_name.as_str());
+ merge_codegen_units(tcx, &mut initial_partitioning, count, &tcx.crate_name.as_str());
debug_dump(tcx, "POST MERGING:", initial_partitioning.codegen_units.iter());
}
}
}
-fn merge_codegen_units<'tcx>(initial_partitioning: &mut PreInliningPartitioning<'tcx>,
+fn merge_codegen_units<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
+ initial_partitioning: &mut PreInliningPartitioning<'tcx>,
target_cgu_count: usize,
crate_name: &str) {
assert!(target_cgu_count >= 1);
// the stable sort below will keep everything nice and deterministic.
codegen_units.sort_by_key(|cgu| cgu.name().clone());
+ // Estimate the size of a codegen unit as (approximately) the number of MIR
+ // statements it corresponds to.
+ fn codegen_unit_size_estimate<'a, 'tcx>(cgu: &CodegenUnit<'tcx>,
+ mono_item_sizes: &HashMap<MonoItem, usize>)
+ -> usize {
+ cgu.items().keys().map(|mi| mono_item_sizes.get(mi).unwrap()).sum()
+ }
+
+ fn mono_item_size_estimate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
+ item: &MonoItem<'tcx>)
+ -> usize {
+ match item {
+ MonoItem::Fn(instance) => {
+ // Estimate the size of a function based on how many statements
+ // it contains.
+ let mir = tcx.instance_mir(instance.def);
+ mir.basic_blocks().iter().map(|bb| bb.statements.len()).sum()
+ },
+ // Conservatively estimate the size of a static declaration
+ // or assembly to be 1.
+ MonoItem::Static(_) | MonoItem::GlobalAsm(_) => 1,
+ }
+ }
+
+ // Since `sort_by_key` currently recomputes the keys for each comparison,
+ // we can save unnecessary recomputations by storing size estimates for
+ // each `MonoItem`. Storing estimates for `CodegenUnit` might be preferable,
+ // but its structure makes it awkward to use as a key and additionally their
+ // sizes change as the merging occurs, requiring the map to be updated.
+ let mut sizes: HashMap<MonoItem, usize> = HashMap::new();
+ for mis in codegen_units.iter().map(|cgu| cgu.items().keys()) {
+ mis.for_each(|mi| {
+ sizes.entry(*mi).or_insert_with(|| mono_item_size_estimate(tcx, mi));
+ });
+ }
+
// Merge the two smallest codegen units until the target size is reached.
// Note that "size" is estimated here rather inaccurately as the number of
// translation items in a given unit. This could be improved on.
while codegen_units.len() > target_cgu_count {
// Sort small cgus to the back
- codegen_units.sort_by_key(|cgu| -(cgu.items().len() as i64));
+ codegen_units.sort_by_key(|cgu| usize::MAX - codegen_unit_size_estimate(cgu, &sizes));
let mut smallest = codegen_units.pop().unwrap();
let second_smallest = codegen_units.last_mut().unwrap();