Auto merge of #45472 - michaelwoerister:incr-comp-caching-base, r=nikomatsakis

incr.comp.: Implement compiler diagnostic persistence.

This PR implements storing and loading diagnostics that the compiler generates and thus allows for emitting warnings during incremental compilation without actually re-evaluating the thing the warning originally came from. It also lays some groundwork for storing and loading type information and MIR in the incr. comp. cache.

~~It is still work in progress:~~
- ~~There's still some documentation to be added.~~
- ~~The way anonymous queries are handled might lead to duplicated emissions of warnings. Not sure if there is a better way or how frequent such duplication would be in practice.~~

Diagnostic message duplication is addressed separately in #45519.

r? @nikomatsakis

1 files changed, 37 insertions, 0 deletions

diff --git a/src/libsyntax/codemap.rs b/src/libsyntax/codemap.rs
index dd46903bb88..ad78c550cf6 100644
--- a/src/libsyntax/codemap.rs
+++ b/src/libsyntax/codemap.rs
@@ -17,11 +17,15 @@
 //! within the CodeMap, which upon request can be converted to line and column
 //! information, source code snippets, etc.
 
+
 pub use syntax_pos::*;
 pub use syntax_pos::hygiene::{ExpnFormat, ExpnInfo, NameAndSpan};
 pub use self::ExpnFormat::*;
 
+use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::stable_hasher::StableHasher;
 use std::cell::{RefCell, Ref};
+use std::hash::Hash;
 use std::path::{Path, PathBuf};
 use std::rc::Rc;
 
@@ -98,6 +102,24 @@ impl FileLoader for RealFileLoader {
     }
 }
 
+// This is a FileMap identifier that is used to correlate FileMaps between
+// subsequent compilation sessions (which is something we need to do during
+// incremental compilation).
+#[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
+pub struct StableFilemapId(u128);
+
+impl StableFilemapId {
+    pub fn new(filemap: &FileMap) -> StableFilemapId {
+        let mut hasher = StableHasher::new();
+
+        filemap.name.hash(&mut hasher);
+        filemap.name_was_remapped.hash(&mut hasher);
+        filemap.unmapped_path.hash(&mut hasher);
+
+        StableFilemapId(hasher.finish())
+    }
+}
+
 // _____________________________________________________________________________
 // CodeMap
 //
@@ -108,6 +130,7 @@ pub struct CodeMap {
     // This is used to apply the file path remapping as specified via
     // -Zremap-path-prefix to all FileMaps allocated within this CodeMap.
     path_mapping: FilePathMapping,
+    stable_id_to_filemap: RefCell<FxHashMap<StableFilemapId, Rc<FileMap>>>,
 }
 
 impl CodeMap {
@@ -116,6 +139,7 @@ impl CodeMap {
             files: RefCell::new(Vec::new()),
             file_loader: Box::new(RealFileLoader),
             path_mapping,
+            stable_id_to_filemap: RefCell::new(FxHashMap()),
         }
     }
 
@@ -126,6 +150,7 @@ impl CodeMap {
             files: RefCell::new(Vec::new()),
             file_loader,
             path_mapping,
+            stable_id_to_filemap: RefCell::new(FxHashMap()),
         }
     }
 
@@ -146,6 +171,10 @@ impl CodeMap {
         self.files.borrow()
     }
 
+    pub fn filemap_by_stable_id(&self, stable_id: StableFilemapId) -> Option<Rc<FileMap>> {
+        self.stable_id_to_filemap.borrow().get(&stable_id).map(|fm| fm.clone())
+    }
+
     fn next_start_pos(&self) -> usize {
         let files = self.files.borrow();
         match files.last() {
@@ -180,6 +209,10 @@ impl CodeMap {
 
         files.push(filemap.clone());
 
+        self.stable_id_to_filemap
+            .borrow_mut()
+            .insert(StableFilemapId::new(&filemap), filemap.clone());
+
         filemap
     }
 
@@ -241,6 +274,10 @@ impl CodeMap {
 
         files.push(filemap.clone());
 
+        self.stable_id_to_filemap
+            .borrow_mut()
+            .insert(StableFilemapId::new(&filemap), filemap.clone());
+
         filemap
     }