Auto merge of #35854 - nikomatsakis:incr-comp-cache-hash-35549, r=mw

compute and cache HIR hashes at beginning

This avoids the compile-time overhead of computing them twice.  It also fixes
an issue where the hash computed after typeck is differen than the hash before,
because typeck mutates the def-map in place.

Fixes #35549.
Fixes #35593.

Some performance measurements suggest this `HashesMap` is very small in memory (unobservable via `-Z time-passes`) and very cheap to construct. I do see some (very minor) performance wins in the incremental case after the first run -- the first run costs more because loading the dep-graph didn't have any hashing to do in that case. Example timings from two runs  of `libsyntex-syntax` -- the (1) indicates first run, (2) indicates second run, and (*) indicates both together:

| Phase | Master | Branch |
| ---- | ---- | ---- |
| compute_hashes_map (1) | N/A | 0.343 |
| load_dep_graph (1) | 0 | 0 |
| serialize dep graph (1) | 4.190 | 3.920 |
| total (1) | 4.190 | 4.260 |
| compute_hashes_map (2) | N/A | 0.344 |
| load_dep_graph (2) | 0.592 | 0.252 |
| serialize dep graph (2) | 4.119 | 3.779 |
| total (2) | 4.71 | 4.375 |
| total (*) | 8.9 | 8.635 |

r? @michaelwoerister

src/librustc/dep_graph/dep_node.rs

@@ -147,6 +147,11 @@ impl<D: Clone + Debug> DepNode<D> {
             }
         }
 
+        if label == "Krate" {
+            // special case
+            return Ok(DepNode::Krate);
+        }
+
         check! {
             CollectItem,
             BorrowCheck,

src/librustc/hir/mod.rs

@@ -1621,7 +1621,7 @@ pub type FreevarMap = NodeMap<Vec<Freevar>>;
 
 pub type CaptureModeMap = NodeMap<CaptureClause>;
 
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 pub struct TraitCandidate {
     pub def_id: DefId,
     pub import_id: Option<NodeId>,

src/librustc_driver/driver.rs

@@ -26,7 +26,7 @@ use rustc::util::common::time;
 use rustc::util::nodemap::NodeSet;
 use rustc_back::sha2::{Sha256, Digest};
 use rustc_borrowck as borrowck;
-use rustc_incremental;
+use rustc_incremental::{self, IncrementalHashesMap};
 use rustc_resolve::{MakeGlobMap, Resolver};
 use rustc_metadata::macro_import;
 use rustc_metadata::creader::read_local_crates;
@@ -172,7 +172,7 @@ pub fn compile_input(sess: &Session,
                                     resolutions,
                                     &arenas,
                                     &crate_name,
-                                    |tcx, mir_map, analysis, result| {
+                                    |tcx, mir_map, analysis, incremental_hashes_map, result| {
             {
                 // Eventually, we will want to track plugins.
                 let _ignore = tcx.dep_graph.in_ignore();
@@ -202,7 +202,8 @@ pub fn compile_input(sess: &Session,
             }
             let trans = phase_4_translate_to_llvm(tcx,
                                                   mir_map.unwrap(),
-                                                  analysis);
+                                                  analysis,
+                                                  &incremental_hashes_map);
 
             if log_enabled!(::log::INFO) {
                 println!("Post-trans");
@@ -797,14 +798,15 @@ pub fn phase_3_run_analysis_passes<'tcx, F, R>(sess: &'tcx Session,
     where F: for<'a> FnOnce(TyCtxt<'a, 'tcx, 'tcx>,
                             Option<MirMap<'tcx>>,
                             ty::CrateAnalysis,
+                            IncrementalHashesMap,
                             CompileResult) -> R
 {
     macro_rules! try_with_f {
-        ($e: expr, ($t: expr, $m: expr, $a: expr)) => {
+        ($e: expr, ($t: expr, $m: expr, $a: expr, $h: expr)) => {
             match $e {
                 Ok(x) => x,
                 Err(x) => {
-                    f($t, $m, $a, Err(x));
+                    f($t, $m, $a, $h, Err(x));
                     return Err(x);
                 }
             }
@@ -860,12 +862,16 @@ pub fn phase_3_run_analysis_passes<'tcx, F, R>(sess: &'tcx Session,
                              index,
                              name,
                              |tcx| {
+        let incremental_hashes_map =
+            time(time_passes,
+                 "compute_incremental_hashes_map",
+                 || rustc_incremental::compute_incremental_hashes_map(tcx));
         time(time_passes,
              "load_dep_graph",
-             || rustc_incremental::load_dep_graph(tcx));
+             || rustc_incremental::load_dep_graph(tcx, &incremental_hashes_map));
 
         // passes are timed inside typeck
-        try_with_f!(typeck::check_crate(tcx), (tcx, None, analysis));
+        try_with_f!(typeck::check_crate(tcx), (tcx, None, analysis, incremental_hashes_map));
 
         time(time_passes,
              "const checking",
@@ -935,7 +941,11 @@ pub fn phase_3_run_analysis_passes<'tcx, F, R>(sess: &'tcx Session,
         // lint warnings and so on -- kindck used to do this abort, but
         // kindck is gone now). -nmatsakis
         if sess.err_count() > 0 {
-            return Ok(f(tcx, Some(mir_map), analysis, Err(sess.err_count())));
+            return Ok(f(tcx,
+                        Some(mir_map),
+                        analysis,
+                        incremental_hashes_map,
+                        Err(sess.err_count())));
         }
 
         analysis.reachable =
@@ -963,17 +973,22 @@ pub fn phase_3_run_analysis_passes<'tcx, F, R>(sess: &'tcx Session,
 
         // The above three passes generate errors w/o aborting
         if sess.err_count() > 0 {
-            return Ok(f(tcx, Some(mir_map), analysis, Err(sess.err_count())));
+            return Ok(f(tcx,
+                        Some(mir_map),
+                        analysis,
+                        incremental_hashes_map,
+                        Err(sess.err_count())));
         }
 
-        Ok(f(tcx, Some(mir_map), analysis, Ok(())))
+        Ok(f(tcx, Some(mir_map), analysis, incremental_hashes_map, Ok(())))
     })
 }
 
 /// Run the translation phase to LLVM, after which the AST and analysis can
 pub fn phase_4_translate_to_llvm<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                            mut mir_map: MirMap<'tcx>,
-                                           analysis: ty::CrateAnalysis)
+                                           analysis: ty::CrateAnalysis,
+                                           incremental_hashes_map: &IncrementalHashesMap)
                                            -> trans::CrateTranslation {
     let time_passes = tcx.sess.time_passes();
 
@@ -1007,15 +1022,15 @@ pub fn phase_4_translate_to_llvm<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     let translation =
         time(time_passes,
              "translation",
-             move || trans::trans_crate(tcx, &mir_map, analysis));
+             move || trans::trans_crate(tcx, &mir_map, analysis, &incremental_hashes_map));
 
     time(time_passes,
          "assert dep graph",
          move || rustc_incremental::assert_dep_graph(tcx));
 
     time(time_passes,
          "serialize dep graph",
-         move || rustc_incremental::save_dep_graph(tcx));
+         move || rustc_incremental::save_dep_graph(tcx, &incremental_hashes_map));
 
     translation
 }

src/librustc_driver/pretty.rs

@@ -234,7 +234,7 @@ impl PpSourceMode {
                                                                  resolutions.clone(),
                                                                  arenas,
                                                                  id,
-                                                                 |tcx, _, _, _| {
+                                                                 |tcx, _, _, _, _| {
                     let annotation = TypedAnnotation {
                         tcx: tcx,
                     };
@@ -951,7 +951,7 @@ fn print_with_analysis<'tcx, 'a: 'tcx>(sess: &'a Session,
                                                      resolutions.clone(),
                                                      arenas,
                                                      crate_name,
-                                                     |tcx, mir_map, _, _| {
+                                                     |tcx, mir_map, _, _, _| {
         match ppm {
             PpmMir | PpmMirCFG => {
                 if let Some(mir_map) = mir_map {

src/librustc_incremental/calculate_svh/def_path_hash.rs

@@ -0,0 +1,36 @@
+// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use rustc::hir::def_id::DefId;
+use rustc::ty::TyCtxt;
+use rustc::util::nodemap::DefIdMap;
+
+pub struct DefPathHashes<'a, 'tcx: 'a> {
+    tcx: TyCtxt<'a, 'tcx, 'tcx>,
+    data: DefIdMap<u64>,
+}
+
+impl<'a, 'tcx> DefPathHashes<'a, 'tcx> {
+    pub fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Self {
+        DefPathHashes {
+            tcx: tcx,
+            data: DefIdMap()
+        }
+    }
+
+    pub fn hash(&mut self, def_id: DefId) -> u64 {
+        let tcx = self.tcx;
+        *self.data.entry(def_id)
+                  .or_insert_with(|| {
+                      let def_path = tcx.def_path(def_id);
+                      def_path.deterministic_hash(tcx)
+                  })
+    }
+}