definitions: Add some timing stats for DefPathTable decoding.

Author: michaelwoerister

src/librustc/session/mod.rs

@@ -136,6 +136,8 @@ pub struct PerfStats {
     pub incr_comp_bytes_hashed: Cell<u64>,
     // The accumulated time spent on computing symbol hashes
     pub symbol_hash_time: Cell<Duration>,
+    // The accumulated time spent decoding def path tables from metadata
+    pub decode_def_path_tables_time: Cell<Duration>,
 }
 
 impl Session {
@@ -501,6 +503,8 @@ impl Session {
                  self.perf_stats.incr_comp_hashes_count.get());
         println!("Total time spent computing symbol hashes:      {}",
                  duration_to_secs_str(self.perf_stats.symbol_hash_time.get()));
+        println!("Total time spent decoding DefPath tables:      {}",
+                 duration_to_secs_str(self.perf_stats.decode_def_path_tables_time.get()));
     }
 }
 
@@ -635,6 +639,7 @@ pub fn build_session_(sopts: config::Options,
             incr_comp_hashes_count: Cell::new(0),
             incr_comp_bytes_hashed: Cell::new(0),
             symbol_hash_time: Cell::new(Duration::from_secs(0)),
+            decode_def_path_tables_time: Cell::new(Duration::from_secs(0)),
         },
         code_stats: RefCell::new(CodeStats::new()),
     };

src/librustc_metadata/creader.rs

@@ -22,6 +22,7 @@ use rustc_back::PanicStrategy;
 use rustc::session::search_paths::PathKind;
 use rustc::middle;
 use rustc::middle::cstore::{CrateStore, validate_crate_name, ExternCrate};
+use rustc::util::common::record_time;
 use rustc::util::nodemap::FxHashSet;
 use rustc::middle::cstore::NativeLibrary;
 use rustc::hir::map::Definitions;
@@ -297,10 +298,14 @@ impl<'a> CrateLoader<'a> {
 
         let cnum_map = self.resolve_crate_deps(root, &crate_root, &metadata, cnum, span, dep_kind);
 
+        let def_path_table = record_time(&self.sess.perf_stats.decode_def_path_tables_time, || {
+            crate_root.def_path_table.decode(&metadata)
+        });
+
         let mut cmeta = cstore::CrateMetadata {
             name: name,
             extern_crate: Cell::new(None),
-            def_path_table: crate_root.def_path_table.decode(&metadata),
+            def_path_table: def_path_table,
             proc_macros: crate_root.macro_derive_registrar.map(|_| {
                 self.load_derive_macros(&crate_root, dylib.clone().map(|p| p.0), span)
             }),