diff --git a/cranelift/src/libfilecheck/checker.rs b/cranelift/src/libfilecheck/checker.rs
index 6bb458b55e..a2af0815e7 100644
--- a/cranelift/src/libfilecheck/checker.rs
+++ b/cranelift/src/libfilecheck/checker.rs
@@ -2,6 +2,7 @@ use error::{Error, Result};
 use variable::{VariableMap, Value, varname_prefix};
 use pattern::Pattern;
 use regex::{Regex, Captures};
+use std::borrow::Cow;
 use std::collections::HashMap;
 use std::cmp::max;
 use std::fmt::{self, Display, Formatter};
@@ -183,7 +184,7 @@ impl Checker {
                 Directive::Regex(ref var, ref rx) => {
                     state.vars.insert(var.clone(),
                                       VarDef {
-                                          value: Value::Regex(rx.clone()),
+                                          value: Value::Regex(Cow::Borrowed(rx)),
                                           offset: 0,
                                       });
                     continue;
@@ -234,9 +235,9 @@ impl Checker {
 }
 
 /// A local definition of a variable.
-pub struct VarDef {
+pub struct VarDef<'a> {
     /// The value given to the variable.
-    value: Value,
+    value: Value<'a>,
     /// Offset in input text from where the variable is available.
     offset: usize,
 }
@@ -246,7 +247,7 @@ struct State<'a> {
     env_vars: &'a VariableMap,
     recorder: &'a mut Recorder,
 
-    vars: HashMap<String, VarDef>,
+    vars: HashMap<String, VarDef<'a>>,
     // Offset after the last ordered match. This does not include recent unordered matches.
     last_ordered: usize,
     // Largest offset following a positive match, including unordered matches.
@@ -331,7 +332,7 @@ impl<'a> State<'a> {
                     let txtval = caps.name(var).unwrap_or("");
                     self.recorder.defined_var(var, txtval);
                     let vardef = VarDef {
-                        value: Value::Text(txtval.to_string()),
+                        value: Value::Text(Cow::Borrowed(txtval)),
                         // This offset is the end of the whole matched pattern, not just the text
                         // defining the variable.
                         offset: range.0 + matched_range.1,
diff --git a/cranelift/src/libfilecheck/pattern.rs b/cranelift/src/libfilecheck/pattern.rs
index 69464bd7c8..88c47011f9 100644
--- a/cranelift/src/libfilecheck/pattern.rs
+++ b/cranelift/src/libfilecheck/pattern.rs
@@ -330,19 +330,14 @@ impl Pattern {
                 Part::DefLit { ref regex, .. } => out.push_str(regex),
                 Part::DefVar { def, ref var } => {
                     // Wrap regex in a named capture group.
-                    write!(out,
-                           "(?P<{}>{})",
-                           self.defs[def],
-                           match vmap.lookup(var) {
-                               None => {
-                                   return Err(Error::UndefVariable(format!("undefined variable \
-                                                                            ${}",
-                                                                           var)))
-                               }
-                               Some(Value::Text(s)) => quote(&s),
-                               Some(Value::Regex(rx)) => rx,
-                           })
-                        .unwrap()
+                    write!(out, "(?P<{}>", self.defs[def]).unwrap();
+                    match vmap.lookup(var) {
+                        None => {
+                            return Err(Error::UndefVariable(format!("undefined variable ${}", var)))
+                        }
+                        Some(Value::Text(s)) => write!(out, "{})", quote(&s[..])).unwrap(),
+                        Some(Value::Regex(rx)) => write!(out, "{})", rx).unwrap(),
+                    }
                 }
             }
 
diff --git a/cranelift/src/libfilecheck/variable.rs b/cranelift/src/libfilecheck/variable.rs
index 7238249146..51bc38fc07 100644
--- a/cranelift/src/libfilecheck/variable.rs
+++ b/cranelift/src/libfilecheck/variable.rs
@@ -1,3 +1,5 @@
+use std::borrow::Cow;
+
 /// A variable name is one or more ASCII alphanumerical characters, including underscore.
 /// Note that numerical variable names like `$45` are allowed too.
 ///
@@ -16,9 +18,9 @@ pub fn varname_prefix(s: &str) -> usize {
 
 /// A variable can contain either a regular expression or plain text.
 #[derive(Debug, Clone, PartialEq, Eq)]
-pub enum Value {
-    Text(String),
-    Regex(String),
+pub enum Value<'a> {
+    Text(Cow<'a, str>),
+    Regex(Cow<'a, str>),
 }
 
 /// Resolve variables by name.