Revert "Merge CrateDisambiguator into StableCrateId"

This reverts commit d0ec85d3fb6d322496cb8f4bc1c21e19f23284ad.

2 files changed, 40 insertions, 8 deletions

diff --git a/compiler/rustc_interface/src/passes.rs b/compiler/rustc_interface/src/passes.rs
index b1f89fd42cc..aa7af609fb5 100644
--- a/compiler/rustc_interface/src/passes.rs
+++ b/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(
-        crate_name,
-        sess.crate_types().contains(&CrateType::Executable),
-        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)?;
+    let disambiguator = util::compute_crate_disambiguator(sess);
+    sess.crate_disambiguator.set(disambiguator).expect("not yet initialized");
+    rustc_incremental::prepare_session_directory(sess, &crate_name, disambiguator)?;
 
     if sess.opts.incremental.is_some() {
         sess.time("incr_comp_garbage_collect_session_directories", || {
diff --git a/compiler/rustc_interface/src/util.rs b/compiler/rustc_interface/src/util.rs
index d1d0eee365d..6485fbebd66 100644
--- a/compiler/rustc_interface/src/util.rs
+++ b/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],