Use FxHash{Map,Set} instead of the default Hash{Map,Set} everywhere in rustc.

src/librustc_errors/emitter.rs

@@ -16,12 +16,12 @@ use {Level, CodeSuggestion, DiagnosticBuilder, SubDiagnostic, SourceMapperDyn, D
 use snippet::{Annotation, AnnotationType, Line, MultilineAnnotation, StyledString, Style};
 use styled_buffer::StyledBuffer;
 
+use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync::Lrc;
 use atty;
 use std::borrow::Cow;
 use std::io::prelude::*;
 use std::io;
-use std::collections::HashMap;
 use std::cmp::{min, Reverse};
 use termcolor::{StandardStream, ColorChoice, ColorSpec, BufferWriter};
 use termcolor::{WriteColor, Color, Buffer};
@@ -1090,7 +1090,7 @@ impl EmitterWriter {
                                             max_line_num_len + 1);
 
                 // Contains the vertical lines' positions for active multiline annotations
-                let mut multilines = HashMap::new();
+                let mut multilines = FxHashMap::default();
 
                 // Next, output the annotate source for this file
                 for line_idx in 0..annotated_file.lines.len() {
@@ -1109,7 +1109,7 @@ impl EmitterWriter {
                                                          width_offset,
                                                          code_offset);
 
-                    let mut to_add = HashMap::new();
+                    let mut to_add = FxHashMap::default();
 
                     for (depth, style) in depths {
                         if multilines.get(&depth).is_some() {

src/librustc_errors/registry.rs

@@ -8,11 +8,11 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use std::collections::HashMap;
+use rustc_data_structures::fx::FxHashMap;
 
 #[derive(Clone)]
 pub struct Registry {
-    descriptions: HashMap<&'static str, &'static str>,
+    descriptions: FxHashMap<&'static str, &'static str>,
 }
 
 impl Registry {