[WIP] rustc_span: Symbol perf experiments

Cargo.lock

@@ -3910,6 +3910,7 @@ dependencies = [
 name = "rustc_macros"
 version = "0.1.0"
 dependencies = [
+ "phf_codegen",
  "proc-macro2",
  "quote",
  "syn",
@@ -4197,6 +4198,7 @@ version = "0.0.0"
 dependencies = [
  "cfg-if 0.1.10",
  "md-5",
+ "phf",
  "rustc_arena",
  "rustc_data_structures",
  "rustc_index",

compiler/rustc_macros/Cargo.toml

@@ -10,5 +10,6 @@ proc-macro = true
 [dependencies]
 synstructure = "0.12.1"
 syn = { version = "1", features = ["full"] }
+phf_codegen = "0.8"
 proc-macro2 = "1"
 quote = "1"

compiler/rustc_macros/src/symbols.rs

@@ -28,8 +28,8 @@ use std::collections::HashMap;
 use syn::parse::{Parse, ParseStream, Result};
 use syn::{braced, punctuated::Punctuated, Ident, LitStr, Token};
 
-#[cfg(test)]
-mod tests;
+// #[cfg(test)]
+// mod tests;
 
 mod kw {
     syn::custom_keyword!(Keywords);
@@ -127,6 +127,7 @@ fn symbols_with_errors(input: TokenStream) -> (TokenStream, Vec<syn::Error>) {
     let mut keyword_stream = quote! {};
     let mut symbols_stream = quote! {};
     let mut prefill_stream = quote! {};
+    let mut symbol_strings = Vec::new();
     let mut counter = 0u32;
     let mut keys =
         HashMap::<String, Span>::with_capacity(input.keywords.len() + input.symbols.len() + 10);
@@ -163,6 +164,7 @@ fn symbols_with_errors(input: TokenStream) -> (TokenStream, Vec<syn::Error>) {
         keyword_stream.extend(quote! {
             pub const #name: Symbol = Symbol::new(#counter);
         });
+        symbol_strings.push(value_string);
         counter += 1;
     }
 
@@ -182,6 +184,7 @@ fn symbols_with_errors(input: TokenStream) -> (TokenStream, Vec<syn::Error>) {
         symbols_stream.extend(quote! {
             pub const #name: Symbol = Symbol::new(#counter);
         });
+        symbol_strings.push(value);
         counter += 1;
     }
 
@@ -194,9 +197,19 @@ fn symbols_with_errors(input: TokenStream) -> (TokenStream, Vec<syn::Error>) {
         prefill_stream.extend(quote! {
             #n,
         });
+        symbol_strings.push(n);
     }
     let _ = counter; // for future use
 
+    // Build the PHF map. This translates from strings to Symbol values.
+    let mut phf_map = phf_codegen::Map::<&str>::new();
+    for (symbol_index, symbol) in symbol_strings.iter().enumerate() {
+        phf_map.entry(symbol, format!("Symbol::new({})", symbol_index as u32).as_str());
+    }
+    let phf_map_built = phf_map.build();
+    let phf_map_text = phf_map_built.to_string();
+    let phf_map_expr = syn::parse_str::<syn::Expr>(&phf_map_text).unwrap();
+
     let output = quote! {
         const SYMBOL_DIGITS_BASE: u32 = #digits_base;
 
@@ -222,6 +235,8 @@ fn symbols_with_errors(input: TokenStream) -> (TokenStream, Vec<syn::Error>) {
                 ])
             }
         }
+
+        static STATIC_SYMBOLS_PHF: ::phf::Map<&'static str, Symbol> = #phf_map_expr;
     };
 
     (output, errors.list)

compiler/rustc_span/Cargo.toml

@@ -20,3 +20,4 @@ tracing = "0.1"
 sha-1 = "0.9"
 sha2 = "0.9"
 md-5 = "0.9"
+phf = "0.8"

compiler/rustc_span/src/lib.rs

@@ -18,10 +18,12 @@
 #![feature(crate_visibility_modifier)]
 #![feature(const_fn)]
 #![feature(const_panic)]
+#![feature(hash_raw_entry)]
 #![feature(negative_impls)]
 #![feature(nll)]
 #![feature(min_specialization)]
 #![feature(option_expect_none)]
+#![feature(zzz)]
 
 #[macro_use]
 extern crate rustc_macros;