Revert "Merge CrateDisambiguator into StableCrateId"

This reverts commit d0ec85d3fb.

compiler/rustc_hir/src/definitions.rs

@@ -14,6 +14,7 @@ use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::stable_hasher::StableHasher;
 use rustc_data_structures::unhash::UnhashMap;
 use rustc_index::vec::IndexVec;
+use rustc_span::crate_disambiguator::CrateDisambiguator;
 use rustc_span::hygiene::ExpnId;
 use rustc_span::symbol::{kw, sym, Symbol};
 
@@ -338,7 +339,7 @@ impl Definitions {
     }
 
     /// Adds a root definition (no parent) and a few other reserved definitions.
-    pub fn new(stable_crate_id: StableCrateId) -> Definitions {
+    pub fn new(crate_name: &str, crate_disambiguator: CrateDisambiguator) -> Definitions {
         let key = DefKey {
             parent: None,
             disambiguated_data: DisambiguatedDefPathData {
@@ -347,6 +348,7 @@ impl Definitions {
             },
         };
 
+        let stable_crate_id = StableCrateId::new(crate_name, crate_disambiguator);
         let parent_hash = DefPathHash::new(stable_crate_id, 0);
         let def_path_hash = key.compute_stable_hash(parent_hash);
 

compiler/rustc_incremental/src/persist/fs.rs

@@ -108,7 +108,7 @@ use rustc_data_structures::svh::Svh;
 use rustc_data_structures::{base_n, flock};
 use rustc_errors::ErrorReported;
 use rustc_fs_util::{link_or_copy, LinkOrCopy};
-use rustc_session::{Session, StableCrateId};
+use rustc_session::{CrateDisambiguator, Session};
 
 use std::fs as std_fs;
 use std::io;
@@ -189,7 +189,7 @@ pub fn in_incr_comp_dir(incr_comp_session_dir: &Path, file_name: &str) -> PathBu
 pub fn prepare_session_directory(
     sess: &Session,
     crate_name: &str,
-    stable_crate_id: StableCrateId,
+    crate_disambiguator: CrateDisambiguator,
 ) -> Result<(), ErrorReported> {
     if sess.opts.incremental.is_none() {
         return Ok(());
@@ -200,7 +200,7 @@ pub fn prepare_session_directory(
     debug!("prepare_session_directory");
 
     // {incr-comp-dir}/{crate-name-and-disambiguator}
-    let crate_dir = crate_path(sess, crate_name, stable_crate_id);
+    let crate_dir = crate_path(sess, crate_name, crate_disambiguator);
     debug!("crate-dir: {}", crate_dir.display());
     create_dir(sess, &crate_dir, "crate")?;
 
@@ -648,12 +648,19 @@ fn string_to_timestamp(s: &str) -> Result<SystemTime, ()> {
     Ok(UNIX_EPOCH + duration)
 }
 
-fn crate_path(sess: &Session, crate_name: &str, stable_crate_id: StableCrateId) -> PathBuf {
+fn crate_path(
+    sess: &Session,
+    crate_name: &str,
+    crate_disambiguator: CrateDisambiguator,
+) -> PathBuf {
     let incr_dir = sess.opts.incremental.as_ref().unwrap().clone();
 
-    let stable_crate_id = base_n::encode(stable_crate_id.to_u64() as u128, INT_ENCODE_BASE);
+    // The full crate disambiguator is really long. 64 bits of it should be
+    // sufficient.
+    let crate_disambiguator = crate_disambiguator.to_fingerprint().to_smaller_hash();
+    let crate_disambiguator = base_n::encode(crate_disambiguator as u128, INT_ENCODE_BASE);
 
-    let crate_name = format!("{}-{}", crate_name, stable_crate_id);
+    let crate_name = format!("{}-{}", crate_name, crate_disambiguator);
     incr_dir.join(crate_name)
 }
 

compiler/rustc_interface/src/passes.rs

@@ -12,7 +12,7 @@ use rustc_data_structures::temp_dir::MaybeTempDir;
 use rustc_data_structures::{box_region_allow_access, declare_box_region_type, parallel};
 use rustc_errors::{ErrorReported, PResult};
 use rustc_expand::base::ExtCtxt;
-use rustc_hir::def_id::{StableCrateId, LOCAL_CRATE};
+use rustc_hir::def_id::LOCAL_CRATE;
 use rustc_hir::Crate;
 use rustc_lint::LintStore;
 use rustc_metadata::creader::CStore;
@@ -170,13 +170,9 @@ pub fn register_plugins<'a>(
     let crate_types = util::collect_crate_types(sess, &krate.attrs);
     sess.init_crate_types(crate_types);
 
-    let stable_crate_id = StableCrateId::new(
+    let disambiguator = util::compute_crate_disambiguator(sess);
-        crate_name,
+    sess.crate_disambiguator.set(disambiguator).expect("not yet initialized");
-        sess.crate_types().contains(&CrateType::Executable),
+    rustc_incremental::prepare_session_directory(sess, &crate_name, disambiguator)?;
-        sess.opts.cg.metadata.clone(),
-    );
-    sess.stable_crate_id.set(stable_crate_id).expect("not yet initialized");
-    rustc_incremental::prepare_session_directory(sess, &crate_name, stable_crate_id)?;
 
     if sess.opts.incremental.is_some() {
         sess.time("incr_comp_garbage_collect_session_directories", || {

compiler/rustc_interface/src/util.rs

@@ -2,9 +2,11 @@ use rustc_ast::mut_visit::{visit_clobber, MutVisitor, *};
 use rustc_ast::ptr::P;
 use rustc_ast::{self as ast, AttrVec, BlockCheckMode};
 use rustc_codegen_ssa::traits::CodegenBackend;
+use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 #[cfg(parallel_compiler)]
 use rustc_data_structures::jobserver;
+use rustc_data_structures::stable_hasher::StableHasher;
 use rustc_data_structures::sync::Lrc;
 use rustc_errors::registry::Registry;
 use rustc_metadata::dynamic_lib::DynamicLibrary;
@@ -16,6 +18,7 @@ use rustc_session::config::{self, CrateType};
 use rustc_session::config::{ErrorOutputType, Input, OutputFilenames};
 use rustc_session::lint::{self, BuiltinLintDiagnostics, LintBuffer};
 use rustc_session::parse::CrateConfig;
+use rustc_session::CrateDisambiguator;
 use rustc_session::{early_error, filesearch, output, DiagnosticOutput, Session};
 use rustc_span::edition::Edition;
 use rustc_span::lev_distance::find_best_match_for_name;
@@ -484,6 +487,39 @@ pub fn get_codegen_sysroot(
     }
 }
 
+pub(crate) fn compute_crate_disambiguator(session: &Session) -> CrateDisambiguator {
+    use std::hash::Hasher;
+
+    // The crate_disambiguator is a 128 bit hash. The disambiguator is fed
+    // into various other hashes quite a bit (symbol hashes, incr. comp. hashes,
+    // debuginfo type IDs, etc), so we don't want it to be too wide. 128 bits
+    // should still be safe enough to avoid collisions in practice.
+    let mut hasher = StableHasher::new();
+
+    let mut metadata = session.opts.cg.metadata.clone();
+    // We don't want the crate_disambiguator to dependent on the order
+    // -C metadata arguments, so sort them:
+    metadata.sort();
+    // Every distinct -C metadata value is only incorporated once:
+    metadata.dedup();
+
+    hasher.write(b"metadata");
+    for s in &metadata {
+        // Also incorporate the length of a metadata string, so that we generate
+        // different values for `-Cmetadata=ab -Cmetadata=c` and
+        // `-Cmetadata=a -Cmetadata=bc`
+        hasher.write_usize(s.len());
+        hasher.write(s.as_bytes());
+    }
+
+    // Also incorporate crate type, so that we don't get symbol conflicts when
+    // linking against a library of the same name, if this is an executable.
+    let is_exe = session.crate_types().contains(&CrateType::Executable);
+    hasher.write(if is_exe { b"exe" } else { b"lib" });
+
+    CrateDisambiguator::from(hasher.finish::<Fingerprint>())
+}
+
 pub(crate) fn check_attr_crate_type(
     sess: &Session,
     attrs: &[ast::Attribute],

compiler/rustc_metadata/src/creader.rs

@@ -21,7 +21,7 @@ use rustc_session::config::{self, CrateType, ExternLocation};
 use rustc_session::lint::{self, BuiltinLintDiagnostics, ExternDepSpec};
 use rustc_session::output::validate_crate_name;
 use rustc_session::search_paths::PathKind;
-use rustc_session::Session;
+use rustc_session::{CrateDisambiguator, Session};
 use rustc_span::edition::Edition;
 use rustc_span::symbol::{sym, Symbol};
 use rustc_span::{Span, DUMMY_SP};
@@ -222,8 +222,10 @@ impl<'a> CrateLoader<'a> {
         metadata_loader: &'a MetadataLoaderDyn,
         local_crate_name: &str,
     ) -> Self {
+        let local_crate_stable_id =
+            StableCrateId::new(local_crate_name, sess.local_crate_disambiguator());
         let mut stable_crate_ids = FxHashMap::default();
-        stable_crate_ids.insert(sess.local_stable_crate_id(), LOCAL_CRATE);
+        stable_crate_ids.insert(local_crate_stable_id, LOCAL_CRATE);
 
         CrateLoader {
             sess,
@@ -325,14 +327,17 @@ impl<'a> CrateLoader<'a> {
 
     fn verify_no_symbol_conflicts(&self, root: &CrateRoot<'_>) -> Result<(), CrateError> {
         // Check for (potential) conflicts with the local crate
-        if self.sess.local_stable_crate_id() == root.stable_crate_id() {
+        if self.local_crate_name == root.name()
+            && self.sess.local_crate_disambiguator() == root.disambiguator()
+        {
             return Err(CrateError::SymbolConflictsCurrent(root.name()));
         }
 
         // Check for conflicts with any crate loaded so far
         let mut res = Ok(());
         self.cstore.iter_crate_data(|_, other| {
-            if other.stable_crate_id() == root.stable_crate_id() && // same stable crate id
+            if other.name() == root.name() && // same crate-name
+               other.disambiguator() == root.disambiguator() && // same crate-disambiguator
                other.hash() != root.hash()
             {
                 // but different SVH
@@ -406,7 +411,7 @@ impl<'a> CrateLoader<'a> {
                 None => (&source, &crate_root),
             };
             let dlsym_dylib = dlsym_source.dylib.as_ref().expect("no dylib for a proc-macro crate");
-            Some(self.dlsym_proc_macros(&dlsym_dylib.0, dlsym_root.stable_crate_id())?)
+            Some(self.dlsym_proc_macros(&dlsym_dylib.0, dlsym_root.disambiguator())?)
         } else {
             None
         };
@@ -659,7 +664,7 @@ impl<'a> CrateLoader<'a> {
     fn dlsym_proc_macros(
         &self,
         path: &Path,
-        stable_crate_id: StableCrateId,
+        disambiguator: CrateDisambiguator,
     ) -> Result<&'static [ProcMacro], CrateError> {
         // Make sure the path contains a / or the linker will search for it.
         let path = env::current_dir().unwrap().join(path);
@@ -668,7 +673,7 @@ impl<'a> CrateLoader<'a> {
             Err(s) => return Err(CrateError::DlOpen(s)),
         };
 
-        let sym = self.sess.generate_proc_macro_decls_symbol(stable_crate_id);
+        let sym = self.sess.generate_proc_macro_decls_symbol(disambiguator);
         let decls = unsafe {
             let sym = match lib.symbol(&sym) {
                 Ok(f) => f,

compiler/rustc_metadata/src/locator.rs

@@ -226,7 +226,7 @@ use rustc_session::config::{self, CrateType};
 use rustc_session::filesearch::{FileDoesntMatch, FileMatches, FileSearch};
 use rustc_session::search_paths::PathKind;
 use rustc_session::utils::CanonicalizedPath;
-use rustc_session::{Session, StableCrateId};
+use rustc_session::{CrateDisambiguator, Session};
 use rustc_span::symbol::{sym, Symbol};
 use rustc_span::Span;
 use rustc_target::spec::{Target, TargetTriple};
@@ -787,7 +787,7 @@ pub fn find_plugin_registrar(
     metadata_loader: &dyn MetadataLoader,
     span: Span,
     name: Symbol,
-) -> (PathBuf, StableCrateId) {
+) -> (PathBuf, CrateDisambiguator) {
     match find_plugin_registrar_impl(sess, metadata_loader, name) {
         Ok(res) => res,
         // `core` is always available if we got as far as loading plugins.
@@ -799,7 +799,7 @@ fn find_plugin_registrar_impl<'a>(
     sess: &'a Session,
     metadata_loader: &dyn MetadataLoader,
     name: Symbol,
-) -> Result<(PathBuf, StableCrateId), CrateError> {
+) -> Result<(PathBuf, CrateDisambiguator), CrateError> {
     info!("find plugin registrar `{}`", name);
     let mut locator = CrateLocator::new(
         sess,
@@ -816,7 +816,7 @@ fn find_plugin_registrar_impl<'a>(
 
     match locator.maybe_load_library_crate()? {
         Some(library) => match library.source.dylib {
-            Some(dylib) => Ok((dylib.0, library.metadata.get_root().stable_crate_id())),
+            Some(dylib) => Ok((dylib.0, library.metadata.get_root().disambiguator())),
             None => Err(CrateError::NonDylibPlugin(name)),
         },
         None => Err(locator.into_error()),

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -620,6 +620,10 @@ impl CrateRoot<'_> {
         self.name
     }
 
+    crate fn disambiguator(&self) -> CrateDisambiguator {
+        self.disambiguator
+    }
+
     crate fn hash(&self) -> Svh {
         self.hash
     }
@@ -1923,8 +1927,8 @@ impl CrateMetadata {
         self.root.name
     }
 
-    crate fn stable_crate_id(&self) -> StableCrateId {
+    crate fn disambiguator(&self) -> CrateDisambiguator {
-        self.root.stable_crate_id
+        self.root.disambiguator
     }
 
     crate fn hash(&self) -> Svh {

compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs

@@ -19,7 +19,7 @@ use rustc_middle::middle::stability::DeprecationEntry;
 use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::{self, TyCtxt, Visibility};
 use rustc_session::utils::NativeLibKind;
-use rustc_session::{Session, StableCrateId};
+use rustc_session::{CrateDisambiguator, Session};
 use rustc_span::source_map::{Span, Spanned};
 use rustc_span::symbol::Symbol;
 
@@ -186,6 +186,7 @@ provide! { <'tcx> tcx, def_id, other, cdata,
     }
     native_libraries => { Lrc::new(cdata.get_native_libraries(tcx.sess)) }
     foreign_modules => { cdata.get_foreign_modules(tcx) }
+    crate_disambiguator => { cdata.root.disambiguator }
     crate_hash => { cdata.root.hash }
     crate_host_hash => { cdata.host_hash }
     crate_name => { cdata.root.name }
@@ -488,8 +489,8 @@ impl CrateStore for CStore {
         self.get_crate_data(cnum).root.name
     }
 
-    fn stable_crate_id_untracked(&self, cnum: CrateNum) -> StableCrateId {
+    fn crate_disambiguator_untracked(&self, cnum: CrateNum) -> CrateDisambiguator {
-        self.get_crate_data(cnum).root.stable_crate_id
+        self.get_crate_data(cnum).root.disambiguator
     }
 
     fn crate_hash_untracked(&self, cnum: CrateNum) -> Svh {

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -671,6 +671,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             extra_filename: tcx.sess.opts.cg.extra_filename.clone(),
             triple: tcx.sess.opts.target_triple.clone(),
             hash: tcx.crate_hash(LOCAL_CRATE),
+            disambiguator: tcx.sess.local_crate_disambiguator(),
             stable_crate_id: tcx.def_path_hash(LOCAL_CRATE.as_def_id()).stable_crate_id(),
             panic_strategy: tcx.sess.panic_strategy(),
             edition: tcx.sess.edition(),

compiler/rustc_metadata/src/rmeta/mod.rs

@@ -18,6 +18,7 @@ use rustc_middle::mir;
 use rustc_middle::ty::{self, ReprOptions, Ty};
 use rustc_serialize::opaque::Encoder;
 use rustc_session::config::SymbolManglingVersion;
+use rustc_session::CrateDisambiguator;
 use rustc_span::edition::Edition;
 use rustc_span::hygiene::MacroKind;
 use rustc_span::symbol::{Ident, Symbol};
@@ -201,6 +202,7 @@ crate struct CrateRoot<'tcx> {
     triple: TargetTriple,
     extra_filename: String,
     hash: Svh,
+    disambiguator: CrateDisambiguator,
     stable_crate_id: StableCrateId,
     panic_strategy: PanicStrategy,
     edition: Edition,

compiler/rustc_middle/src/dep_graph/dep_node.rs

@@ -285,7 +285,7 @@ pub type DepNode = rustc_query_system::dep_graph::DepNode<DepKind>;
 // required that their size stay the same, but we don't want to change
 // it inadvertently. This assert just ensures we're aware of any change.
 #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
-static_assert_size!(DepNode, 17);
+static_assert_size!(DepNode, 18);
 
 #[cfg(not(any(target_arch = "x86", target_arch = "x86_64")))]
 static_assert_size!(DepNode, 24);

compiler/rustc_middle/src/hir/map/mod.rs

@@ -15,7 +15,6 @@ use rustc_hir::intravisit::Visitor;
 use rustc_hir::itemlikevisit::ItemLikeVisitor;
 use rustc_hir::*;
 use rustc_index::vec::Idx;
-use rustc_span::def_id::StableCrateId;
 use rustc_span::hygiene::MacroKind;
 use rustc_span::source_map::Spanned;
 use rustc_span::symbol::{kw, Ident, Symbol};
@@ -991,24 +990,25 @@ pub(super) fn crate_hash(tcx: TyCtxt<'_>, crate_num: CrateNum) -> Svh {
     upstream_crates.hash_stable(&mut hcx, &mut stable_hasher);
     source_file_names.hash_stable(&mut hcx, &mut stable_hasher);
     tcx.sess.opts.dep_tracking_hash(true).hash_stable(&mut hcx, &mut stable_hasher);
-    tcx.sess.local_stable_crate_id().hash_stable(&mut hcx, &mut stable_hasher);
+    tcx.sess.local_crate_disambiguator().to_fingerprint().hash_stable(&mut hcx, &mut stable_hasher);
     tcx.untracked_crate.non_exported_macro_attrs.hash_stable(&mut hcx, &mut stable_hasher);
 
     let crate_hash: Fingerprint = stable_hasher.finish();
     Svh::new(crate_hash.to_smaller_hash())
 }
 
-fn upstream_crates(cstore: &dyn CrateStore) -> Vec<(StableCrateId, Svh)> {
+fn upstream_crates(cstore: &dyn CrateStore) -> Vec<(Symbol, Fingerprint, Svh)> {
     let mut upstream_crates: Vec<_> = cstore
         .crates_untracked()
         .iter()
         .map(|&cnum| {
-            let stable_crate_id = cstore.stable_crate_id_untracked(cnum);
+            let name = cstore.crate_name_untracked(cnum);
+            let disambiguator = cstore.crate_disambiguator_untracked(cnum).to_fingerprint();
             let hash = cstore.crate_hash_untracked(cnum);
-            (stable_crate_id, hash)
+            (name, disambiguator, hash)
         })
         .collect();
-    upstream_crates.sort_unstable_by_key(|&(stable_crate_id, _)| stable_crate_id);
+    upstream_crates.sort_unstable_by_key(|&(name, dis, _)| (name.as_str(), dis));
     upstream_crates
 }
 

compiler/rustc_middle/src/middle/cstore.rs

@@ -14,7 +14,7 @@ use rustc_hir::definitions::{DefKey, DefPath, DefPathHash};
 use rustc_macros::HashStable;
 use rustc_session::search_paths::PathKind;
 use rustc_session::utils::NativeLibKind;
-use rustc_session::StableCrateId;
+use rustc_session::CrateDisambiguator;
 use rustc_span::symbol::Symbol;
 use rustc_span::Span;
 use rustc_target::spec::Target;
@@ -206,7 +206,7 @@ pub trait CrateStore {
 
     // "queries" used in resolve that aren't tracked for incremental compilation
     fn crate_name_untracked(&self, cnum: CrateNum) -> Symbol;
-    fn stable_crate_id_untracked(&self, cnum: CrateNum) -> StableCrateId;
+    fn crate_disambiguator_untracked(&self, cnum: CrateNum) -> CrateDisambiguator;
     fn crate_hash_untracked(&self, cnum: CrateNum) -> Svh;
 
     // This is basically a 1-based range of ints, which is a little

compiler/rustc_middle/src/middle/exported_symbols.rs

@@ -48,8 +48,8 @@ impl<'tcx> ExportedSymbol<'tcx> {
 
 pub fn metadata_symbol_name(tcx: TyCtxt<'_>) -> String {
     format!(
-        "rust_metadata_{}_{:08x}",
+        "rust_metadata_{}_{}",
         tcx.crate_name(LOCAL_CRATE),
-        tcx.sess.local_stable_crate_id().to_u64(),
+        tcx.crate_disambiguator(LOCAL_CRATE).to_fingerprint().to_hex()
     )
 }

compiler/rustc_middle/src/mir/mono.rs

@@ -490,18 +490,15 @@ impl CodegenUnitNameBuilder<'tcx> {
             // local crate's ID. Otherwise there can be collisions between CGUs
             // instantiating stuff for upstream crates.
             let local_crate_id = if cnum != LOCAL_CRATE {
-                let local_stable_crate_id = tcx.sess.local_stable_crate_id();
+                let local_crate_disambiguator = format!("{}", tcx.crate_disambiguator(LOCAL_CRATE));
-                format!(
+                format!("-in-{}.{}", tcx.crate_name(LOCAL_CRATE), &local_crate_disambiguator[0..8])
-                    "-in-{}.{:08x}",
-                    tcx.crate_name(LOCAL_CRATE),
-                    local_stable_crate_id.to_u64()
-                )
             } else {
                 String::new()
             };
 
-            let stable_crate_id = tcx.sess.local_stable_crate_id();
+            let crate_disambiguator = tcx.crate_disambiguator(cnum).to_string();
-            format!("{}.{:08x}{}", tcx.crate_name(cnum), stable_crate_id.to_u64(), local_crate_id)
+            // Using a shortened disambiguator of about 40 bits
+            format!("{}.{}{}", tcx.crate_name(cnum), &crate_disambiguator[0..8], local_crate_id)
         });
 
         write!(cgu_name, "{}", crate_prefix).unwrap();

compiler/rustc_middle/src/query/mod.rs

@@ -1237,6 +1237,10 @@ rustc_queries! {
     query proc_macro_decls_static(_: ()) -> Option<LocalDefId> {
         desc { "looking up the derive registrar for a crate" }
     }
+    query crate_disambiguator(_: CrateNum) -> CrateDisambiguator {
+        eval_always
+        desc { "looking up the disambiguator a crate" }
+    }
     // The macro which defines `rustc_metadata::provide_extern` depends on this query's name.
     // Changing the name should cause a compiler error, but in case that changes, be aware.
     query crate_hash(_: CrateNum) -> Svh {

compiler/rustc_middle/src/ty/context.rs

@@ -1275,24 +1275,24 @@ impl<'tcx> TyCtxt<'tcx> {
 
     pub fn def_path_debug_str(self, def_id: DefId) -> String {
         // We are explicitly not going through queries here in order to get
-        // crate name and stable crate id since this code is called from debug!()
+        // crate name and disambiguator since this code is called from debug!()
         // statements within the query system and we'd run into endless
         // recursion otherwise.
-        let (crate_name, stable_crate_id) = if def_id.is_local() {
+        let (crate_name, crate_disambiguator) = if def_id.is_local() {
-            (self.crate_name, self.sess.local_stable_crate_id())
+            (self.crate_name, self.sess.local_crate_disambiguator())
         } else {
             (
                 self.cstore.crate_name_untracked(def_id.krate),
-                self.def_path_hash(def_id.krate.as_def_id()).stable_crate_id(),
+                self.cstore.crate_disambiguator_untracked(def_id.krate),
             )
         };
 
         format!(
             "{}[{}]{}",
             crate_name,
-            // Don't print the whole stable crate id. That's just
+            // Don't print the whole crate disambiguator. That's just
             // annoying in debug output.
-            &(format!("{:08x}", stable_crate_id.to_u64()))[..4],
+            &(crate_disambiguator.to_fingerprint().to_hex())[..4],
             self.def_path(def_id).to_string_no_crate_verbose()
         )
     }

compiler/rustc_middle/src/ty/query/mod.rs

@@ -47,6 +47,7 @@ use rustc_index::{bit_set::FiniteBitSet, vec::IndexVec};
 use rustc_serialize::opaque;
 use rustc_session::config::{EntryFnType, OptLevel, OutputFilenames, SymbolManglingVersion};
 use rustc_session::utils::NativeLibKind;
+use rustc_session::CrateDisambiguator;
 use rustc_target::spec::PanicStrategy;
 
 use rustc_ast as ast;

compiler/rustc_middle/src/ty/query/on_disk_cache.rs

@@ -18,7 +18,7 @@ use rustc_serialize::{
     opaque::{self, FileEncodeResult, FileEncoder, IntEncodedWithFixedSize},
     Decodable, Decoder, Encodable, Encoder,
 };
-use rustc_session::{Session, StableCrateId};
+use rustc_session::{CrateDisambiguator, Session};
 use rustc_span::hygiene::{
     ExpnDataDecodeMode, ExpnDataEncodeMode, ExpnId, HygieneDecodeContext, HygieneEncodeContext,
     SyntaxContext, SyntaxContextData,
@@ -52,7 +52,7 @@ pub struct OnDiskCache<'sess> {
     // session.
     current_diagnostics: Lock<FxHashMap<DepNodeIndex, Vec<Diagnostic>>>,
 
-    prev_cnums: Vec<(u32, StableCrateId)>,
+    prev_cnums: Vec<(u32, String, CrateDisambiguator)>,
     cnum_map: OnceCell<IndexVec<CrateNum, Option<CrateNum>>>,
 
     source_map: &'sess SourceMap,
@@ -120,7 +120,7 @@ pub struct OnDiskCache<'sess> {
 #[derive(Encodable, Decodable)]
 struct Footer {
     file_index_to_stable_id: FxHashMap<SourceFileIndex, StableSourceFileId>,
-    prev_cnums: Vec<(u32, StableCrateId)>,
+    prev_cnums: Vec<(u32, String, CrateDisambiguator)>,
     query_result_index: EncodedQueryResultIndex,
     diagnostics_index: EncodedQueryResultIndex,
     // The location of all allocations.
@@ -349,8 +349,9 @@ impl<'sess> OnDiskCache<'sess> {
             let prev_cnums: Vec<_> = sorted_cnums
                 .iter()
                 .map(|&cnum| {
-                    let stable_crate_id = tcx.def_path_hash(cnum.as_def_id()).stable_crate_id();
+                    let crate_name = tcx.crate_name(cnum).to_string();
-                    (cnum.as_u32(), stable_crate_id)
+                    let crate_disambiguator = tcx.crate_disambiguator(cnum);
+                    (cnum.as_u32(), crate_name, crate_disambiguator)
                 })
                 .collect();
 
@@ -574,23 +575,25 @@ impl<'sess> OnDiskCache<'sess> {
     // maps to None.
     fn compute_cnum_map(
         tcx: TyCtxt<'_>,
-        prev_cnums: &[(u32, StableCrateId)],
+        prev_cnums: &[(u32, String, CrateDisambiguator)],
     ) -> IndexVec<CrateNum, Option<CrateNum>> {
         tcx.dep_graph.with_ignore(|| {
             let current_cnums = tcx
                 .all_crate_nums(())
                 .iter()
                 .map(|&cnum| {
-                    let stable_crate_id = tcx.def_path_hash(cnum.as_def_id()).stable_crate_id();
+                    let crate_name = tcx.crate_name(cnum).to_string();
-                    (stable_crate_id, cnum)
+                    let crate_disambiguator = tcx.crate_disambiguator(cnum);
+                    ((crate_name, crate_disambiguator), cnum)
                 })
                 .collect::<FxHashMap<_, _>>();
 
             let map_size = prev_cnums.iter().map(|&(cnum, ..)| cnum).max().unwrap_or(0) + 1;
             let mut map = IndexVec::from_elem_n(None, map_size as usize);
 
-            for &(prev_cnum, stable_crate_id) in prev_cnums {
+            for &(prev_cnum, ref crate_name, crate_disambiguator) in prev_cnums {
-                map[CrateNum::from_u32(prev_cnum)] = current_cnums.get(&stable_crate_id).cloned();
+                let key = (crate_name.clone(), crate_disambiguator);
+                map[CrateNum::from_u32(prev_cnum)] = current_cnums.get(&key).cloned();
             }
 
             map[LOCAL_CRATE] = Some(LOCAL_CRATE);

compiler/rustc_resolve/src/lib.rs

@@ -1222,7 +1222,7 @@ impl<'a> Resolver<'a> {
         let mut module_map = FxHashMap::default();
         module_map.insert(root_local_def_id, graph_root);
 
-        let definitions = Definitions::new(session.local_stable_crate_id());
+        let definitions = Definitions::new(crate_name, session.local_crate_disambiguator());
         let root = definitions.get_root_def();
 
         let mut visibilities = FxHashMap::default();

compiler/rustc_save_analysis/src/dump_visitor.rs

@@ -142,7 +142,12 @@ impl<'tcx> DumpVisitor<'tcx> {
         let data = CratePreludeData {
             crate_id: GlobalCrateId {
                 name: name.into(),
-                disambiguator: (self.tcx.sess.local_stable_crate_id().to_u64(), 0),
+                disambiguator: self
+                    .tcx
+                    .sess
+                    .local_crate_disambiguator()
+                    .to_fingerprint()
+                    .as_value(),
             },
             crate_root: crate_root.unwrap_or_else(|| "<no source>".to_owned()),
             external_crates: self.save_ctxt.get_external_crates(),

compiler/rustc_save_analysis/src/lib.rs

@@ -127,10 +127,7 @@ impl<'tcx> SaveContext<'tcx> {
                 num: n.as_u32(),
                 id: GlobalCrateId {
                     name: self.tcx.crate_name(n).to_string(),
-                    disambiguator: (
+                    disambiguator: self.tcx.crate_disambiguator(n).to_fingerprint().as_value(),
-                        self.tcx.def_path_hash(n.as_def_id()).stable_crate_id().to_u64(),
-                        0,
-                    ),
                 },
             });
         }

compiler/rustc_session/src/session.rs

@@ -22,7 +22,7 @@ use rustc_errors::json::JsonEmitter;
 use rustc_errors::registry::Registry;
 use rustc_errors::{Diagnostic, DiagnosticBuilder, DiagnosticId, ErrorReported};
 use rustc_lint_defs::FutureBreakage;
-pub use rustc_span::def_id::StableCrateId;
+pub use rustc_span::crate_disambiguator::CrateDisambiguator;
 use rustc_span::source_map::{FileLoader, MultiSpan, RealFileLoader, SourceMap, Span};
 use rustc_span::{edition::Edition, RealFileName};
 use rustc_span::{sym, SourceFileHashAlgorithm, Symbol};
@@ -133,12 +133,12 @@ pub struct Session {
     /// in order to avoid redundantly verbose output (Issue #24690, #44953).
     pub one_time_diagnostics: Lock<FxHashSet<(DiagnosticMessageId, Option<Span>, String)>>,
     crate_types: OnceCell<Vec<CrateType>>,
-    /// The `stable_crate_id` is constructed out of the crate name and all the
+    /// The `crate_disambiguator` is constructed out of all the `-C metadata`
-    /// `-C metadata` arguments passed to the compiler. Its value forms a unique
+    /// arguments passed to the compiler. Its value together with the crate-name
-    /// global identifier for the crate. It is used to allow multiple crates
+    /// forms a unique global identifier for the crate. It is used to allow
-    /// with the same name to coexist. See the
+    /// multiple crates with the same name to coexist. See the
     /// `rustc_codegen_llvm::back::symbol_names` module for more information.
-    pub stable_crate_id: OnceCell<StableCrateId>,
+    pub crate_disambiguator: OnceCell<CrateDisambiguator>,
 
     features: OnceCell<rustc_feature::Features>,
 
@@ -335,8 +335,8 @@ impl Session {
         self.parse_sess.span_diagnostic.emit_future_breakage_report(diags_and_breakage);
     }
 
-    pub fn local_stable_crate_id(&self) -> StableCrateId {
+    pub fn local_crate_disambiguator(&self) -> CrateDisambiguator {
-        self.stable_crate_id.get().copied().unwrap()
+        self.crate_disambiguator.get().copied().unwrap()
     }
 
     pub fn crate_types(&self) -> &[CrateType] {
@@ -833,12 +833,12 @@ impl Session {
 
     /// Returns the symbol name for the registrar function,
     /// given the crate `Svh` and the function `DefIndex`.
-    pub fn generate_plugin_registrar_symbol(&self, stable_crate_id: StableCrateId) -> String {
+    pub fn generate_plugin_registrar_symbol(&self, disambiguator: CrateDisambiguator) -> String {
-        format!("__rustc_plugin_registrar_{:08x}__", stable_crate_id.to_u64())
+        format!("__rustc_plugin_registrar_{}__", disambiguator.to_fingerprint().to_hex())
     }
 
-    pub fn generate_proc_macro_decls_symbol(&self, stable_crate_id: StableCrateId) -> String {
+    pub fn generate_proc_macro_decls_symbol(&self, disambiguator: CrateDisambiguator) -> String {
-        format!("__rustc_proc_macro_decls_{:08x}__", stable_crate_id.to_u64())
+        format!("__rustc_proc_macro_decls_{}__", disambiguator.to_fingerprint().to_hex())
     }
 
     pub fn target_filesearch(&self, kind: PathKind) -> filesearch::FileSearch<'_> {
@@ -1397,7 +1397,7 @@ pub fn build_session(
         working_dir,
         one_time_diagnostics: Default::default(),
         crate_types: OnceCell::new(),
-        stable_crate_id: OnceCell::new(),
+        crate_disambiguator: OnceCell::new(),
         features: OnceCell::new(),
         lint_store: OnceCell::new(),
         recursion_limit: OnceCell::new(),

compiler/rustc_span/src/crate_disambiguator.rs

@@ -0,0 +1,35 @@
+// This is here because `rustc_session` wants to refer to it,
+// and so does `rustc_hir`, but `rustc_hir` shouldn't refer to `rustc_session`.
+
+use rustc_data_structures::fingerprint::Fingerprint;
+use rustc_data_structures::{base_n, impl_stable_hash_via_hash};
+
+use std::fmt;
+
+/// Hash value constructed out of all the `-C metadata` arguments passed to the
+/// compiler. Together with the crate-name forms a unique global identifier for
+/// the crate.
+#[derive(Eq, PartialEq, Ord, PartialOrd, Hash, Debug, Clone, Copy, Encodable, Decodable)]
+pub struct CrateDisambiguator(Fingerprint);
+
+impl CrateDisambiguator {
+    pub fn to_fingerprint(self) -> Fingerprint {
+        self.0
+    }
+}
+
+impl fmt::Display for CrateDisambiguator {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
+        let (a, b) = self.0.as_value();
+        let as_u128 = a as u128 | ((b as u128) << 64);
+        f.write_str(&base_n::encode(as_u128, base_n::CASE_INSENSITIVE))
+    }
+}
+
+impl From<Fingerprint> for CrateDisambiguator {
+    fn from(fingerprint: Fingerprint) -> CrateDisambiguator {
+        CrateDisambiguator(fingerprint)
+    }
+}
+
+impl_stable_hash_via_hash!(CrateDisambiguator);

compiler/rustc_span/src/def_id.rs

@@ -1,3 +1,4 @@
+use crate::crate_disambiguator::CrateDisambiguator;
 use crate::HashStableContext;
 use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
@@ -126,51 +127,26 @@ impl Borrow<Fingerprint> for DefPathHash {
     }
 }
 
-/// A [StableCrateId] is a 64 bit hash of the crate name combined with all
+/// A [StableCrateId] is a 64 bit hash of `(crate-name, crate-disambiguator)`. It
-/// `-Cmetadata` arguments. It is to [CrateNum] what [DefPathHash] is to
+/// is to [CrateNum] what [DefPathHash] is to [DefId]. It is stable across
-/// [DefId]. It is stable across compilation sessions.
+/// compilation sessions.
 ///
 /// Since the ID is a hash value there is a (very small) chance that two crates
 /// end up with the same [StableCrateId]. The compiler will check for such
 /// collisions when loading crates and abort compilation in order to avoid
 /// further trouble.
-#[derive(Copy, Clone, Hash, PartialEq, Eq, PartialOrd, Ord, Debug)]
+#[derive(Copy, Clone, Hash, PartialEq, Eq, PartialOrd, Ord, Debug, Encodable, Decodable)]
-#[derive(HashStable_Generic, Encodable, Decodable)]
 pub struct StableCrateId(u64);
 
 impl StableCrateId {
-    pub fn to_u64(self) -> u64 {
-        self.0
-    }
-
     /// Computes the stable ID for a crate with the given name and
-    /// `-Cmetadata` arguments.
+    /// disambiguator.
-    pub fn new(crate_name: &str, is_exe: bool, mut metadata: Vec<String>) -> StableCrateId {
+    pub fn new(crate_name: &str, crate_disambiguator: CrateDisambiguator) -> StableCrateId {
         use std::hash::Hash;
-        use std::hash::Hasher;
 
         let mut hasher = StableHasher::new();
         crate_name.hash(&mut hasher);
-
+        crate_disambiguator.hash(&mut hasher);
-        // We don't want the stable crate id to dependent on the order
-        // -C metadata arguments, so sort them:
-        metadata.sort();
-        // Every distinct -C metadata value is only incorporated once:
-        metadata.dedup();
-
-        hasher.write(b"metadata");
-        for s in &metadata {
-            // Also incorporate the length of a metadata string, so that we generate
-            // different values for `-Cmetadata=ab -Cmetadata=c` and
-            // `-Cmetadata=a -Cmetadata=bc`
-            hasher.write_usize(s.len());
-            hasher.write(s.as_bytes());
-        }
-
-        // Also incorporate crate type, so that we don't get symbol conflicts when
-        // linking against a library of the same name, if this is an executable.
-        hasher.write(if is_exe { b"exe" } else { b"lib" });
-
         StableCrateId(hasher.finish())
     }
 }

compiler/rustc_span/src/lib.rs

@@ -45,6 +45,8 @@ pub mod lev_distance;
 mod span_encoding;
 pub use span_encoding::{Span, DUMMY_SP};
 
+pub mod crate_disambiguator;
+
 pub mod symbol;
 pub use symbol::{sym, Symbol};
 

compiler/rustc_symbol_mangling/src/legacy.rs

@@ -126,9 +126,8 @@ fn get_symbol_hash<'tcx>(
         substs.hash_stable(&mut hcx, &mut hasher);
 
         if let Some(instantiating_crate) = instantiating_crate {
-            tcx.def_path_hash(instantiating_crate.as_def_id())
+            tcx.crate_name(instantiating_crate).as_str().hash_stable(&mut hcx, &mut hasher);
-                .stable_crate_id()
+            tcx.crate_disambiguator(instantiating_crate).hash_stable(&mut hcx, &mut hasher);
-                .hash_stable(&mut hcx, &mut hasher);
         }
 
         // We want to avoid accidental collision between different types of instances.

compiler/rustc_symbol_mangling/src/lib.rs

@@ -165,12 +165,12 @@ fn compute_symbol_name(
     // FIXME(eddyb) Precompute a custom symbol name based on attributes.
     let is_foreign = if let Some(def_id) = def_id.as_local() {
         if tcx.plugin_registrar_fn(()) == Some(def_id) {
-            let stable_crate_id = tcx.sess.local_stable_crate_id();
+            let disambiguator = tcx.sess.local_crate_disambiguator();
-            return tcx.sess.generate_plugin_registrar_symbol(stable_crate_id);
+            return tcx.sess.generate_plugin_registrar_symbol(disambiguator);
         }
         if tcx.proc_macro_decls_static(()) == Some(def_id) {
-            let stable_crate_id = tcx.sess.local_stable_crate_id();
+            let disambiguator = tcx.sess.local_crate_disambiguator();
-            return tcx.sess.generate_proc_macro_decls_symbol(stable_crate_id);
+            return tcx.sess.generate_proc_macro_decls_symbol(disambiguator);
         }
         let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
         matches!(tcx.hir().get(hir_id), Node::ForeignItem(_))

compiler/rustc_symbol_mangling/src/v0.rs

@@ -592,8 +592,8 @@ impl Printer<'tcx> for SymbolMangler<'tcx> {
 
     fn path_crate(mut self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
         self.push("C");
-        let stable_crate_id = self.tcx.def_path_hash(cnum.as_def_id()).stable_crate_id();
+        let fingerprint = self.tcx.crate_disambiguator(cnum).to_fingerprint();
-        self.push_disambiguator(stable_crate_id.to_u64());
+        self.push_disambiguator(fingerprint.to_smaller_hash());
         let name = self.tcx.crate_name(cnum).as_str();
         self.push_ident(&name);
         Ok(self)

compiler/rustc_ty_utils/src/ty.rs

@@ -1,11 +1,12 @@
 use rustc_data_structures::fx::FxIndexSet;
 use rustc_hir as hir;
-use rustc_hir::def_id::{DefId, LocalDefId};
+use rustc_hir::def_id::{CrateNum, DefId, LocalDefId, LOCAL_CRATE};
 use rustc_middle::hir::map as hir_map;
 use rustc_middle::ty::subst::Subst;
 use rustc_middle::ty::{
     self, Binder, Predicate, PredicateKind, ToPredicate, Ty, TyCtxt, WithConstness,
 };
+use rustc_session::CrateDisambiguator;
 use rustc_span::Span;
 use rustc_trait_selection::traits;
 
@@ -387,6 +388,11 @@ fn param_env_reveal_all_normalized(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamE
     tcx.param_env(def_id).with_reveal_all_normalized(tcx)
 }
 
+fn crate_disambiguator(tcx: TyCtxt<'_>, crate_num: CrateNum) -> CrateDisambiguator {
+    assert_eq!(crate_num, LOCAL_CRATE);
+    tcx.sess.local_crate_disambiguator()
+}
+
 fn instance_def_size_estimate<'tcx>(
     tcx: TyCtxt<'tcx>,
     instance_def: ty::InstanceDef<'tcx>,
@@ -532,6 +538,7 @@ pub fn provide(providers: &mut ty::query::Providers) {
         param_env,
         param_env_reveal_all_normalized,
         trait_of_item,
+        crate_disambiguator,
         instance_def_size_estimate,
         issue33140_self_ty,
         impl_defaultness,