rustc: Remove Session::dep_graph

This commit removes the `dep_graph` field from the `Session` type according to
issue #44390. Most of the fallout here was relatively straightforward and the
`prepare_session_directory` function was rejiggered a bit to reuse the results
in the later-called `load_dep_graph` function.

Closes #44390

src/librustc/hir/lowering.rs

@@ -40,6 +40,7 @@
 //! get confused if the spans from leaf AST nodes occur in multiple places
 //! in the HIR, especially for multiple identifiers.
 
+use dep_graph::DepGraph;
 use hir;
 use hir::map::{Definitions, DefKey};
 use hir::def_id::{DefIndex, DefId, CRATE_DEF_INDEX};
@@ -122,13 +123,14 @@ pub trait Resolver {
 
 pub fn lower_crate(sess: &Session,
                    cstore: &CrateStore,
+                   dep_graph: &DepGraph,
                    krate: &Crate,
                    resolver: &mut Resolver)
                    -> hir::Crate {
     // We're constructing the HIR here; we don't care what we will
     // read, since we haven't even constructed the *input* to
     // incr. comp. yet.
-    let _ignore = sess.dep_graph.in_ignore();
+    let _ignore = dep_graph.in_ignore();
 
     LoweringContext {
         crate_root: std_inject::injected_crate_name(krate),

src/librustc/session/config.rs

@@ -1949,7 +1949,6 @@ mod dep_tracking {
 
 #[cfg(test)]
 mod tests {
-    use dep_graph::DepGraph;
     use errors;
     use getopts;
     use lint;
@@ -1982,15 +1981,14 @@ mod tests {
     // When the user supplies --test we should implicitly supply --cfg test
     #[test]
     fn test_switch_implies_cfg_test() {
-        let dep_graph = DepGraph::new(false);
         let matches =
             &match optgroups().parse(&["--test".to_string()]) {
               Ok(m) => m,
               Err(f) => panic!("test_switch_implies_cfg_test: {}", f)
             };
         let registry = errors::registry::Registry::new(&[]);
         let (sessopts, cfg) = build_session_options_and_crate_config(matches);
-        let sess = build_session(sessopts, &dep_graph, None, registry);
+        let sess = build_session(sessopts, None, registry);
         let cfg = build_configuration(&sess, cfg);
         assert!(cfg.contains(&(Symbol::intern("test"), None)));
     }
@@ -1999,7 +1997,6 @@ mod tests {
     // another --cfg test
     #[test]
     fn test_switch_implies_cfg_test_unless_cfg_test() {
-        let dep_graph = DepGraph::new(false);
         let matches =
             &match optgroups().parse(&["--test".to_string(), "--cfg=test".to_string()]) {
               Ok(m) => m,
@@ -2009,7 +2006,7 @@ mod tests {
             };
         let registry = errors::registry::Registry::new(&[]);
         let (sessopts, cfg) = build_session_options_and_crate_config(matches);
-        let sess = build_session(sessopts, &dep_graph, None, registry);
+        let sess = build_session(sessopts, None, registry);
         let cfg = build_configuration(&sess, cfg);
         let mut test_items = cfg.iter().filter(|&&(name, _)| name == "test");
         assert!(test_items.next().is_some());
@@ -2018,14 +2015,13 @@ mod tests {
 
     #[test]
     fn test_can_print_warnings() {
-        let dep_graph = DepGraph::new(false);
         {
             let matches = optgroups().parse(&[
                 "-Awarnings".to_string()
             ]).unwrap();
             let registry = errors::registry::Registry::new(&[]);
             let (sessopts, _) = build_session_options_and_crate_config(&matches);
-            let sess = build_session(sessopts, &dep_graph, None, registry);
+            let sess = build_session(sessopts, None, registry);
             assert!(!sess.diagnostic().can_emit_warnings);
         }
 
@@ -2036,7 +2032,7 @@ mod tests {
             ]).unwrap();
             let registry = errors::registry::Registry::new(&[]);
             let (sessopts, _) = build_session_options_and_crate_config(&matches);
-            let sess = build_session(sessopts, &dep_graph, None, registry);
+            let sess = build_session(sessopts, None, registry);
             assert!(sess.diagnostic().can_emit_warnings);
         }
 
@@ -2046,7 +2042,7 @@ mod tests {
             ]).unwrap();
             let registry = errors::registry::Registry::new(&[]);
             let (sessopts, _) = build_session_options_and_crate_config(&matches);
-            let sess = build_session(sessopts, &dep_graph, None, registry);
+            let sess = build_session(sessopts, None, registry);
             assert!(sess.diagnostic().can_emit_warnings);
         }
     }

src/librustc/session/mod.rs

@@ -11,7 +11,6 @@
 pub use self::code_stats::{CodeStats, DataTypeKind, FieldInfo};
 pub use self::code_stats::{SizeKind, TypeSizeInfo, VariantInfo};
 
-use dep_graph::DepGraph;
 use hir::def_id::{CrateNum, DefIndex};
 
 use lint;
@@ -58,7 +57,6 @@ pub mod search_paths;
 // Represents the data associated with a compilation
 // session for a single crate.
 pub struct Session {
-    pub dep_graph: DepGraph,
     pub target: config::Config,
     pub host: Target,
     pub opts: config::Options,
@@ -91,7 +89,7 @@ pub struct Session {
     // forms a unique global identifier for the crate. It is used to allow
     // multiple crates with the same name to coexist. See the
     // trans::back::symbol_names module for more information.
-    pub crate_disambiguator: RefCell<Symbol>,
+    pub crate_disambiguator: RefCell<Option<Symbol>>,
     pub features: RefCell<feature_gate::Features>,
 
     /// The maximum recursion limit for potentially infinitely recursive
@@ -169,7 +167,10 @@ enum DiagnosticBuilderMethod {
 
 impl Session {
     pub fn local_crate_disambiguator(&self) -> Symbol {
-        *self.crate_disambiguator.borrow()
+        match *self.crate_disambiguator.borrow() {
+            Some(sym) => sym,
+            None => bug!("accessing disambiguator before initialization"),
+        }
     }
     pub fn struct_span_warn<'a, S: Into<MultiSpan>>(&'a self,
                                                     sp: S,
@@ -501,9 +502,29 @@ impl Session {
             kind)
     }
 
+    pub fn set_incr_session_load_dep_graph(&self, load: bool) {
+        let mut incr_comp_session = self.incr_comp_session.borrow_mut();
+
+        match *incr_comp_session {
+            IncrCompSession::Active { ref mut load_dep_graph, .. } => {
+                *load_dep_graph = load;
+            }
+            _ => {}
+        }
+    }
+
+    pub fn incr_session_load_dep_graph(&self) -> bool {
+        let incr_comp_session = self.incr_comp_session.borrow();
+        match *incr_comp_session {
+            IncrCompSession::Active { load_dep_graph, .. } => load_dep_graph,
+            _ => false,
+        }
+    }
+
     pub fn init_incr_comp_session(&self,
                                   session_dir: PathBuf,
-                                  lock_file: flock::Lock) {
+                                  lock_file: flock::Lock,
+                                  load_dep_graph: bool) {
         let mut incr_comp_session = self.incr_comp_session.borrow_mut();
 
         if let IncrCompSession::NotInitialized = *incr_comp_session { } else {
@@ -513,6 +534,7 @@ impl Session {
         *incr_comp_session = IncrCompSession::Active {
             session_directory: session_dir,
             lock_file,
+            load_dep_graph,
         };
     }
 
@@ -617,22 +639,19 @@ impl Session {
 }
 
 pub fn build_session(sopts: config::Options,
-                     dep_graph: &DepGraph,
                      local_crate_source_file: Option<PathBuf>,
                      registry: errors::registry::Registry)
                      -> Session {
     let file_path_mapping = sopts.file_path_mapping();
 
     build_session_with_codemap(sopts,
-                               dep_graph,
                                local_crate_source_file,
                                registry,
                                Rc::new(codemap::CodeMap::new(file_path_mapping)),
                                None)
 }
 
 pub fn build_session_with_codemap(sopts: config::Options,
-                                  dep_graph: &DepGraph,
                                   local_crate_source_file: Option<PathBuf>,
                                   registry: errors::registry::Registry,
                                   codemap: Rc<codemap::CodeMap>,
@@ -672,14 +691,12 @@ pub fn build_session_with_codemap(sopts: config::Options,
                                       emitter);
 
     build_session_(sopts,
-                   dep_graph,
                    local_crate_source_file,
                    diagnostic_handler,
                    codemap)
 }
 
 pub fn build_session_(sopts: config::Options,
-                      dep_graph: &DepGraph,
                       local_crate_source_file: Option<PathBuf>,
                       span_diagnostic: errors::Handler,
                       codemap: Rc<codemap::CodeMap>)
@@ -715,7 +732,6 @@ pub fn build_session_(sopts: config::Options,
     let working_dir = file_path_mapping.map_prefix(working_dir);
 
     let sess = Session {
-        dep_graph: dep_graph.clone(),
         target: target_cfg,
         host,
         opts: sopts,
@@ -735,7 +751,7 @@ pub fn build_session_(sopts: config::Options,
         plugin_attributes: RefCell::new(Vec::new()),
         crate_types: RefCell::new(Vec::new()),
         dependency_formats: RefCell::new(FxHashMap()),
-        crate_disambiguator: RefCell::new(Symbol::intern("")),
+        crate_disambiguator: RefCell::new(None),
         features: RefCell::new(feature_gate::Features::new()),
         recursion_limit: Cell::new(64),
         type_length_limit: Cell::new(1048576),
@@ -793,6 +809,7 @@ pub enum IncrCompSession {
     Active {
         session_directory: PathBuf,
         lock_file: flock::Lock,
+        load_dep_graph: bool,
     },
     // This is the state after the session directory has been finalized. In this
     // state, the contents of the directory must not be modified any more.

src/librustc_driver/driver.rs

@@ -10,6 +10,7 @@
 
 #![cfg_attr(not(feature="llvm"), allow(dead_code))]
 
+use rustc::dep_graph::DepGraph;
 use rustc::hir::{self, map as hir_map};
 use rustc::hir::lowering::lower_crate;
 use rustc::ich::Fingerprint;
@@ -115,7 +116,7 @@ pub fn compile_input(sess: &Session,
     // We need nested scopes here, because the intermediate results can keep
     // large chunks of memory alive and we want to free them as soon as
     // possible to keep the peak memory usage low
-    let (outputs, trans): (OutputFilenames, OngoingCrateTranslation) = {
+    let (outputs, trans, dep_graph): (OutputFilenames, OngoingCrateTranslation, DepGraph) = {
         let krate = match phase_1_parse_input(control, sess, input) {
             Ok(krate) => krate,
             Err(mut parse_error) => {
@@ -144,7 +145,13 @@ pub fn compile_input(sess: &Session,
             ::rustc_trans_utils::link::find_crate_name(Some(sess), &krate.attrs, input);
         let ExpansionResult { expanded_crate, defs, analysis, resolutions, mut hir_forest } = {
             phase_2_configure_and_expand(
-                sess, &cstore, krate, registry, &crate_name, addl_plugins, control.make_glob_map,
+                sess,
+                &cstore,
+                krate,
+                registry,
+                &crate_name,
+                addl_plugins,
+                control.make_glob_map,
                 |expanded_crate| {
                     let mut state = CompileState::state_after_expand(
                         input, sess, outdir, output, &cstore, expanded_crate, &crate_name,
@@ -251,7 +258,7 @@ pub fn compile_input(sess: &Session,
                 }
             }
 
-            Ok((outputs, trans))
+            Ok((outputs, trans, tcx.dep_graph.clone()))
         })??
     };
 
@@ -266,7 +273,7 @@ pub fn compile_input(sess: &Session,
             sess.code_stats.borrow().print_type_sizes();
         }
 
-        let (phase5_result, trans) = phase_5_run_llvm_passes(sess, trans);
+        let (phase5_result, trans) = phase_5_run_llvm_passes(sess, &dep_graph, trans);
 
         controller_entry_point!(after_llvm,
                                 sess,
@@ -624,7 +631,15 @@ pub fn phase_2_configure_and_expand<F>(sess: &Session,
     *sess.features.borrow_mut() = features;
 
     *sess.crate_types.borrow_mut() = collect_crate_types(sess, &krate.attrs);
-    *sess.crate_disambiguator.borrow_mut() = Symbol::intern(&compute_crate_disambiguator(sess));
+
+    let disambiguator = Symbol::intern(&compute_crate_disambiguator(sess));
+    *sess.crate_disambiguator.borrow_mut() = Some(disambiguator);
+    rustc_incremental::prepare_session_directory(
+        sess,
+        &crate_name,
+        &disambiguator.as_str(),
+    );
+    let dep_graph = DepGraph::new(sess.opts.build_dep_graph());
 
     time(time_passes, "recursion limit", || {
         middle::recursion_limit::update_limits(sess, &krate);
@@ -694,7 +709,7 @@ pub fn phase_2_configure_and_expand<F>(sess: &Session,
     // item, much like we do for macro expansion. In other words, the hash reflects not just
     // its contents but the results of name resolution on those contents. Hopefully we'll push
     // this back at some point.
-    let _ignore = sess.dep_graph.in_ignore();
+    let _ignore = dep_graph.in_ignore();
     let mut crate_loader = CrateLoader::new(sess, &cstore, crate_name);
     let resolver_arenas = Resolver::arenas();
     let mut resolver = Resolver::new(sess,
@@ -847,13 +862,13 @@ pub fn phase_2_configure_and_expand<F>(sess: &Session,
 
     // Lower ast -> hir.
     let hir_forest = time(time_passes, "lowering ast -> hir", || {
-        let hir_crate = lower_crate(sess, cstore, &krate, &mut resolver);
+        let hir_crate = lower_crate(sess, cstore, &dep_graph, &krate, &mut resolver);
 
         if sess.opts.debugging_opts.hir_stats {
             hir_stats::print_hir_stats(&hir_crate);
         }
 
-        hir_map::Forest::new(hir_crate, &sess.dep_graph)
+        hir_map::Forest::new(hir_crate, &dep_graph)
     });
 
     time(time_passes,
@@ -1134,17 +1149,18 @@ pub fn phase_4_translate_to_llvm<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 /// as a side effect.
 #[cfg(feature="llvm")]
 pub fn phase_5_run_llvm_passes(sess: &Session,
+                               dep_graph: &DepGraph,
                                trans: write::OngoingCrateTranslation)
                                -> (CompileResult, trans::CrateTranslation) {
-    let trans = trans.join(sess);
+    let trans = trans.join(sess, dep_graph);
 
     if sess.opts.debugging_opts.incremental_info {
         write::dump_incremental_data(&trans);
     }
 
     time(sess.time_passes(),
          "serialize work products",
-         move || rustc_incremental::save_work_products(sess));
+         move || rustc_incremental::save_work_products(sess, dep_graph));
 
     (sess.compile_status(), trans)
 }

src/librustc_driver/lib.rs

@@ -64,7 +64,6 @@ use pretty::{PpMode, UserIdentifiedItem};
 use rustc_resolve as resolve;
 use rustc_save_analysis as save;
 use rustc_save_analysis::DumpHandler;
-use rustc::dep_graph::DepGraph;
 use rustc::session::{self, config, Session, build_session, CompileResult};
 use rustc::session::CompileIncomplete;
 use rustc::session::config::{Input, PrintRequest, OutputType, ErrorOutputType};
@@ -294,13 +293,12 @@ pub fn run_compiler<'a>(args: &[String],
         },
     };
 
-    let dep_graph = DepGraph::new(sopts.build_dep_graph());
     let cstore = Rc::new(CStore::new(box ::MetadataLoader));
 
     let loader = file_loader.unwrap_or(box RealFileLoader);
     let codemap = Rc::new(CodeMap::with_file_loader(loader, sopts.file_path_mapping()));
     let mut sess = session::build_session_with_codemap(
-        sopts, &dep_graph, input_file_path, descriptions, codemap, emitter_dest,
+        sopts, input_file_path, descriptions, codemap, emitter_dest,
     );
     rustc_trans::init(&sess);
     rustc_lint::register_builtins(&mut sess.lint_store.borrow_mut(), Some(&sess));
@@ -318,7 +316,13 @@ pub fn run_compiler<'a>(args: &[String],
 
     let plugins = sess.opts.debugging_opts.extra_plugins.clone();
     let control = callbacks.build_controller(&sess, &matches);
-    (driver::compile_input(&sess, &cstore, &input, &odir, &ofile, Some(plugins), &control),
+    (driver::compile_input(&sess,
+                           &cstore,
+                           &input,
+                           &odir,
+                           &ofile,
+                           Some(plugins),
+                           &control),
      Some(sess))
 }
 
@@ -580,9 +584,7 @@ impl<'a> CompilerCalls<'a> for RustcDefaultCalls {
                     describe_lints(&ls, false);
                     return None;
                 }
-                let dep_graph = DepGraph::new(sopts.build_dep_graph());
                 let mut sess = build_session(sopts.clone(),
-                    &dep_graph,
                     None,
                     descriptions.clone());
                 rustc_trans::init(&sess);