diff --git a/lib/codegen/Cargo.toml b/lib/codegen/Cargo.toml
index b1757f95b5..7c1d2d0e9a 100644
--- a/lib/codegen/Cargo.toml
+++ b/lib/codegen/Cargo.toml
@@ -34,6 +34,9 @@ cranelift-codegen-meta = { path = "meta", version = "0.22.0" }
 default = ["std"]
 std = ["cranelift-entity/std", "cranelift-bforest/std", "target-lexicon/std"]
 core = ["hashmap_core"]
+# This enables some additional functions useful for writing tests, but which
+# can significantly increase the size of the library.
+testing_hooks = []
 
 [badges]
 maintenance = { status = "experimental" }
diff --git a/lib/codegen/src/isa/arm32/mod.rs b/lib/codegen/src/isa/arm32/mod.rs
index 3606c18676..cee753a5f0 100644
--- a/lib/codegen/src/isa/arm32/mod.rs
+++ b/lib/codegen/src/isa/arm32/mod.rs
@@ -7,7 +7,9 @@ mod registers;
 pub mod settings;
 
 use super::super::settings as shared_settings;
-use binemit::{emit_function, CodeSink, MemoryCodeSink};
+#[cfg(feature = "testing_hooks")]
+use binemit::CodeSink;
+use binemit::{emit_function, MemoryCodeSink};
 use ir;
 use isa::enc_tables::{self as shared_enc_tables, lookup_enclist, Encodings};
 use isa::Builder as IsaBuilder;
@@ -111,6 +113,7 @@ impl TargetIsa for Isa {
         abi::allocatable_registers(func)
     }
 
+    #[cfg(feature = "testing_hooks")]
     fn emit_inst(
         &self,
         func: &ir::Function,
diff --git a/lib/codegen/src/isa/arm64/mod.rs b/lib/codegen/src/isa/arm64/mod.rs
index 96e62a9e37..830a109b52 100644
--- a/lib/codegen/src/isa/arm64/mod.rs
+++ b/lib/codegen/src/isa/arm64/mod.rs
@@ -7,7 +7,9 @@ mod registers;
 pub mod settings;
 
 use super::super::settings as shared_settings;
-use binemit::{emit_function, CodeSink, MemoryCodeSink};
+#[cfg(feature = "testing_hooks")]
+use binemit::CodeSink;
+use binemit::{emit_function, MemoryCodeSink};
 use ir;
 use isa::enc_tables::{lookup_enclist, Encodings};
 use isa::Builder as IsaBuilder;
@@ -98,6 +100,7 @@ impl TargetIsa for Isa {
         abi::allocatable_registers(func)
     }
 
+    #[cfg(feature = "testing_hooks")]
     fn emit_inst(
         &self,
         func: &ir::Function,
diff --git a/lib/codegen/src/isa/mod.rs b/lib/codegen/src/isa/mod.rs
index 33e78c96da..c3766346b7 100644
--- a/lib/codegen/src/isa/mod.rs
+++ b/lib/codegen/src/isa/mod.rs
@@ -307,6 +307,10 @@ pub trait TargetIsa: fmt::Display {
     ///
     /// Note that this will call `put*` methods on the `sink` trait object via its vtable which
     /// is not the fastest way of emitting code.
+    ///
+    /// This function is under the "testing_hooks" feature, and is only suitable for use by
+    /// test harnesses. It increases code size, and is inefficient.
+    #[cfg(feature = "testing_hooks")]
     fn emit_inst(
         &self,
         func: &ir::Function,
@@ -316,7 +320,5 @@ pub trait TargetIsa: fmt::Display {
     );
 
     /// Emit a whole function into memory.
-    ///
-    /// This is more performant than calling `emit_inst` for each instruction.
     fn emit_function_to_memory(&self, func: &ir::Function, sink: &mut binemit::MemoryCodeSink);
 }
diff --git a/lib/codegen/src/isa/riscv/mod.rs b/lib/codegen/src/isa/riscv/mod.rs
index 1a09f89bc1..393219571f 100644
--- a/lib/codegen/src/isa/riscv/mod.rs
+++ b/lib/codegen/src/isa/riscv/mod.rs
@@ -7,7 +7,9 @@ mod registers;
 pub mod settings;
 
 use super::super::settings as shared_settings;
-use binemit::{emit_function, CodeSink, MemoryCodeSink};
+#[cfg(feature = "testing_hooks")]
+use binemit::CodeSink;
+use binemit::{emit_function, MemoryCodeSink};
 use ir;
 use isa::enc_tables::{self as shared_enc_tables, lookup_enclist, Encodings};
 use isa::Builder as IsaBuilder;
@@ -105,6 +107,7 @@ impl TargetIsa for Isa {
         abi::allocatable_registers(func, &self.isa_flags)
     }
 
+    #[cfg(feature = "testing_hooks")]
     fn emit_inst(
         &self,
         func: &ir::Function,
diff --git a/lib/codegen/src/isa/x86/mod.rs b/lib/codegen/src/isa/x86/mod.rs
index 0546c648cd..1dfa62bf61 100644
--- a/lib/codegen/src/isa/x86/mod.rs
+++ b/lib/codegen/src/isa/x86/mod.rs
@@ -7,7 +7,9 @@ mod registers;
 pub mod settings;
 
 use super::super::settings as shared_settings;
-use binemit::{emit_function, CodeSink, MemoryCodeSink};
+#[cfg(feature = "testing_hooks")]
+use binemit::CodeSink;
+use binemit::{emit_function, MemoryCodeSink};
 use ir;
 use isa::enc_tables::{self as shared_enc_tables, lookup_enclist, Encodings};
 use isa::Builder as IsaBuilder;
@@ -115,6 +117,7 @@ impl TargetIsa for Isa {
         abi::allocatable_registers(func, &self.triple)
     }
 
+    #[cfg(feature = "testing_hooks")]
     fn emit_inst(
         &self,
         func: &ir::Function,
diff --git a/lib/filetests/Cargo.toml b/lib/filetests/Cargo.toml
index 59c4309563..1ed2daf9e0 100644
--- a/lib/filetests/Cargo.toml
+++ b/lib/filetests/Cargo.toml
@@ -9,7 +9,7 @@ repository = "https://github.com/CraneStation/cranelift"
 publish = false
 
 [dependencies]
-cranelift-codegen = { path = "../codegen", version = "0.22.0" }
+cranelift-codegen = { path = "../codegen", version = "0.22.0", features = ["testing_hooks"] }
 cranelift-reader = { path = "../reader", version = "0.22.0" }
 file-per-thread-logger = "0.1.1"
 filecheck = "0.4.0"