diff --git a/filetests/isa/riscv/encoding.cton b/filetests/isa/riscv/encoding.cton
new file mode 100644
index 0000000000..2ba06007bb
--- /dev/null
+++ b/filetests/isa/riscv/encoding.cton
@@ -0,0 +1,19 @@
+test legalizer
+isa riscv supports_m=1
+
+function int32(i32, i32) {
+ebb0(v1: i32, v2: i32):
+    v10 = iadd v1, v2
+    ; check: [R#0c]
+    ; sameln: $v10 = iadd
+
+    v11 = isub v1, v2
+    ; check: [R#200c]
+    ; sameln: $v11 = isub
+
+    v12 = imul v1, v2
+    ; check: [R#10c]
+    ; sameln: $v12 = imul
+
+    return
+}
diff --git a/src/libcretonne/lib.rs b/src/libcretonne/lib.rs
index f0a328ba8f..26a87bd223 100644
--- a/src/libcretonne/lib.rs
+++ b/src/libcretonne/lib.rs
@@ -7,6 +7,7 @@
 
 pub use verifier::verify_function;
 pub use write::write_function;
+pub use legalizer::legalize_function;
 
 pub const VERSION: &'static str = env!("CARGO_PKG_VERSION");
 
@@ -17,11 +18,11 @@ pub mod dominator_tree;
 pub mod entity_map;
 pub mod settings;
 pub mod verifier;
-pub mod legalizer;
 
 mod write;
 mod constant_hash;
 mod predicates;
+mod legalizer;
 
 #[cfg(test)]
 pub mod test_utils;
diff --git a/src/tools/filetest/legalizer.rs b/src/tools/filetest/legalizer.rs
new file mode 100644
index 0000000000..ea53a703b7
--- /dev/null
+++ b/src/tools/filetest/legalizer.rs
@@ -0,0 +1,45 @@
+//! Test command for checking the IL legalizer.
+//!
+//! The `test legalizer` test command runs each function through `legalize_function()` and sends
+//! the result to filecheck.
+
+use std::borrow::Cow;
+use cretonne::{legalize_function, write_function};
+use cretonne::ir::Function;
+use cton_reader::TestCommand;
+use filetest::subtest::{SubTest, Context, Result, run_filecheck};
+
+struct TestLegalizer;
+
+pub fn subtest(parsed: &TestCommand) -> Result<Box<SubTest>> {
+    assert_eq!(parsed.command, "legalizer");
+    if !parsed.options.is_empty() {
+        Err(format!("No options allowed on {}", parsed))
+    } else {
+        Ok(Box::new(TestLegalizer))
+    }
+}
+
+impl SubTest for TestLegalizer {
+    fn name(&self) -> Cow<str> {
+        Cow::from("legalizer")
+    }
+
+    fn is_mutating(&self) -> bool {
+        true
+    }
+
+    fn needs_isa(&self) -> bool {
+        true
+    }
+
+    fn run(&self, func: Cow<Function>, context: &Context) -> Result<()> {
+        let mut func = func.into_owned();
+        let isa = context.isa.expect("legalizer needs an ISA");
+        legalize_function(&mut func, isa);
+
+        let mut text = String::new();
+        try!(write_function(&mut text, &func, Some(isa)).map_err(|e| e.to_string()));
+        run_filecheck(&text, context)
+    }
+}
diff --git a/src/tools/filetest/mod.rs b/src/tools/filetest/mod.rs
index a924cb04eb..28a9b94d45 100644
--- a/src/tools/filetest/mod.rs
+++ b/src/tools/filetest/mod.rs
@@ -17,6 +17,7 @@ mod runone;
 mod concurrent;
 mod domtree;
 mod verifier;
+mod legalizer;
 
 /// The result of running the test in a file.
 pub type TestResult = Result<time::Duration, String>;
@@ -55,6 +56,7 @@ fn new_subtest(parsed: &TestCommand) -> subtest::Result<Box<subtest::SubTest>> {
         "print-cfg" => print_cfg::subtest(parsed),
         "domtree" => domtree::subtest(parsed),
         "verifier" => verifier::subtest(parsed),
+        "legalizer" => legalizer::subtest(parsed),
         _ => Err(format!("unknown test command '{}'", parsed.command)),
     }
 }