tidy: wrap regexes with lazy_static

yes, once_cell better, but ...

this reduces from

==31349== Total:     1,365,199,543 bytes in 4,774,213 blocks
==31349== At t-gmax: 10,975,708 bytes in 66,093 blocks
==31349== At t-end:  2,880,947 bytes in 12,332 blocks
==31349== Reads:     5,210,008,956 bytes
==31349== Writes:    1,280,920,127 bytes

to

==47796== Total:     821,467,407 bytes in 3,955,595 blocks
==47796== At t-gmax: 10,976,209 bytes in 66,100 blocks
==47796== At t-end:  2,944,016 bytes in 12,490 blocks
==47796== Reads:     4,788,959,023 bytes
==47796== Writes:    975,493,639 bytes

Cargo.lock

@@ -2493,6 +2493,7 @@ dependencies = [
 name = "miropt-test-tools"
 version = "0.1.0"
 dependencies = [
+ "lazy_static",
  "regex",
 ]
 

src/tools/miropt-test-tools/Cargo.toml

@@ -5,3 +5,4 @@ edition = "2021"
 
 [dependencies]
 regex = "1.0"
+lazy_static = "1"

src/tools/miropt-test-tools/src/lib.rs

@@ -1,6 +1,8 @@
 use std::fs;
 use std::path::Path;
 
+use regex::Regex;
+
 pub struct MiroptTestFile {
     pub expected_file: std::path::PathBuf,
     pub from_file: String,
@@ -98,8 +100,11 @@ pub fn files_for_miropt_test(
                 from_file = format!("{}.{}.mir", test_name, first_pass);
                 to_file = Some(second_file);
             } else {
-                let ext_re = regex::Regex::new(r#"(\.(mir|dot|html))$"#).unwrap();
-                let cap = ext_re
+                lazy_static::lazy_static! {
+                    static ref EXT_RE: Regex = Regex::new(r#"(\.(mir|dot|html))$"#).unwrap();
+                }
+
+                let cap = EXT_RE
                     .captures_iter(test_name)
                     .next()
                     .expect("test_name has an invalid extension");

src/tools/tidy/src/style.rs

@@ -127,8 +127,10 @@ fn should_ignore(line: &str) -> bool {
     // Matches test annotations like `//~ ERROR text`.
     // This mirrors the regex in src/tools/compiletest/src/runtest.rs, please
     // update both if either are changed.
-    let re = Regex::new("\\s*//(\\[.*\\])?~.*").unwrap();
-    re.is_match(line) || ANNOTATIONS_TO_IGNORE.iter().any(|a| line.contains(a))
+    lazy_static::lazy_static! {
+        static ref ANNOTATION_RE: Regex = Regex::new("\\s*//(\\[.*\\])?~.*").unwrap();
+    }
+    ANNOTATION_RE.is_match(line) || ANNOTATIONS_TO_IGNORE.iter().any(|a| line.contains(a))
 }
 
 /// Returns `true` if `line` is allowed to be longer than the normal limit.