Add basic benchmark of libproc_macro

Author: dtolnay

Cargo.toml

@@ -42,6 +42,9 @@ nightly = []
 [badges]
 travis-ci = { repository = "alexcrichton/proc-macro2" }
 
+[workspace]
+members = ["benches/bench-libproc-macro"]
+
 [patch.crates-io]
 # Our doc tests depend on quote which depends on proc-macro2. Without this line,
 # the proc-macro2 dependency of quote would be the released version of

benches/bench-libproc-macro/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "bench-libproc-macro"
+version = "0.0.0"
+edition = "2018"
+publish = false
+
+[lib]
+path = "lib.rs"
+proc-macro = true
+
+[[bin]]
+name = "bench-libproc-macro"
+path = "main.rs"

benches/bench-libproc-macro/README.md

@@ -0,0 +1,10 @@
+Example output:
+
+```console
+$ cargo check --release
+
+   Compiling bench-libproc-macro v0.0.0
+STRING: 8 millis
+TOKENSTREAM: 25721 millis
+    Finished release [optimized] target(s) in 26.15s
+```

benches/bench-libproc-macro/lib.rs

@@ -0,0 +1,49 @@
+extern crate proc_macro;
+
+use proc_macro::{Ident, Punct, Spacing, Span, TokenStream, TokenTree};
+use std::iter::once;
+use std::time::Instant;
+
+const N: u32 = 7000;
+
+#[proc_macro]
+pub fn bench(_input: TokenStream) -> TokenStream {
+    let start = Instant::now();
+    let mut string = String::new();
+    for _ in 0..N {
+        string += "core";
+        string += ":";
+        string += ":";
+        string += "option";
+        string += ":";
+        string += ":";
+        string += "Option";
+        string += ":";
+        string += ":";
+        string += "None";
+        string += ",";
+    }
+    string.parse::<TokenStream>().unwrap();
+    eprintln!("STRING: {} millis", start.elapsed().as_millis());
+
+    let start = Instant::now();
+    let span = Span::call_site();
+    let mut tokens = TokenStream::new();
+    for _ in 0..N {
+        // Similar to what is emitted by quote.
+        tokens.extend(once(TokenTree::Ident(Ident::new("core", span))));
+        tokens.extend(once(TokenTree::Punct(Punct::new(':', Spacing::Joint))));
+        tokens.extend(once(TokenTree::Punct(Punct::new(':', Spacing::Alone))));
+        tokens.extend(once(TokenTree::Ident(Ident::new("option", span))));
+        tokens.extend(once(TokenTree::Punct(Punct::new(':', Spacing::Joint))));
+        tokens.extend(once(TokenTree::Punct(Punct::new(':', Spacing::Alone))));
+        tokens.extend(once(TokenTree::Ident(Ident::new("Option", span))));
+        tokens.extend(once(TokenTree::Punct(Punct::new(':', Spacing::Joint))));
+        tokens.extend(once(TokenTree::Punct(Punct::new(':', Spacing::Alone))));
+        tokens.extend(once(TokenTree::Ident(Ident::new("None", span))));
+        tokens.extend(once(TokenTree::Punct(Punct::new(',', Spacing::Joint))));
+    }
+    eprintln!("TOKENSTREAM: {} millis", start.elapsed().as_millis());
+
+    TokenStream::new()
+}

benches/bench-libproc-macro/main.rs

@@ -0,0 +1,3 @@
+bench_libproc_macro::bench!();
+
+fn main() {}