Auto merge of #45912 - Zoxc:par-query, r=<try>

WIP: Playing with adding thread safety to GlobalCtxt

src/libproc_macro/lib.rs

@@ -50,7 +50,7 @@ mod diagnostic;
 pub use diagnostic::{Diagnostic, Level};
 
 use std::{ascii, fmt, iter};
-use std::rc::Rc;
+use std::sync::Arc;
 use std::str::FromStr;
 
 use syntax::ast;
@@ -274,7 +274,7 @@ pub struct LineColumn {
 #[unstable(feature = "proc_macro", issue = "38356")]
 #[derive(Clone)]
 pub struct SourceFile {
-    filemap: Rc<FileMap>,
+    filemap: Arc<FileMap>,
 }
 
 impl SourceFile {
@@ -324,7 +324,7 @@ impl fmt::Debug for SourceFile {
 #[unstable(feature = "proc_macro", issue = "38356")]
 impl PartialEq for SourceFile {
     fn eq(&self, other: &Self) -> bool {
-        Rc::ptr_eq(&self.filemap, &other.filemap)
+        Arc::ptr_eq(&self.filemap, &other.filemap)
     }
 }
 

src/librustc/ich/caching_codemap_view.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use std::rc::Rc;
+use std::sync::Arc;
 use syntax::codemap::CodeMap;
 use syntax_pos::{BytePos, FileMap};
 
@@ -18,7 +18,7 @@ struct CacheEntry {
     line_number: usize,
     line_start: BytePos,
     line_end: BytePos,
-    file: Rc<FileMap>,
+    file: Arc<FileMap>,
     file_index: usize,
 }
 
@@ -51,7 +51,7 @@ impl<'cm> CachingCodemapView<'cm> {
 
     pub fn byte_pos_to_line_and_col(&mut self,
                                     pos: BytePos)
-                                    -> Option<(Rc<FileMap>, usize, BytePos)> {
+                                    -> Option<(Arc<FileMap>, usize, BytePos)> {
         self.time_stamp += 1;
 
         // Check if the position is in one of the cached lines
@@ -78,11 +78,9 @@ impl<'cm> CachingCodemapView<'cm> {
         // If the entry doesn't point to the correct file, fix it up
         if pos < cache_entry.file.start_pos || pos >= cache_entry.file.end_pos {
             let file_valid;
-            let files = self.codemap.files();
-
-            if files.len() > 0 {
+            if self.codemap.files().len() > 0 {
                 let file_index = self.codemap.lookup_filemap_idx(pos);
-                let file = files[file_index].clone();
+                let file = self.codemap.files()[file_index].clone();
 
                 if pos >= file.start_pos && pos < file.end_pos {
                     cache_entry.file = file;

src/librustc/session/config.rs

@@ -1010,6 +1010,8 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
         "prints the llvm optimization passes being run"),
     ast_json: bool = (false, parse_bool, [UNTRACKED],
         "print the AST as JSON and halt"),
+    query_threads: Option<usize> = (None, parse_opt_uint, [UNTRACKED],
+        "execute queries on a thread pool with N threads"),
     ast_json_noexpand: bool = (false, parse_bool, [UNTRACKED],
         "print the pre-expansion AST as JSON and halt"),
     ls: bool = (false, parse_bool, [UNTRACKED],
@@ -1584,6 +1586,10 @@ pub fn build_session_options_and_crate_config(matches: &getopts::Matches)
         }
     }
 
+    if debugging_opts.query_threads == Some(0) {
+        early_error(error_format, "Value for codegen units must be a positive nonzero integer");
+    }
+
     if codegen_units == Some(0) {
         early_error(error_format, "Value for codegen units must be a positive nonzero integer");
     }

src/librustc/session/mod.rs

@@ -657,6 +657,12 @@ impl Session {
         ret
     }
 
+    /// Returns the number of query threads that should be used for this
+    /// compilation
+    pub fn query_threads(&self) -> usize {
+        self.opts.debugging_opts.query_threads.unwrap_or(1)
+    }
+
     /// Returns the number of codegen units that should be used for this
     /// compilation
     pub fn codegen_units(&self) -> usize {