diff --git a/crates/integration/Cargo.toml b/crates/integration/Cargo.toml
index 50d5f55..0b95a1c 100644
--- a/crates/integration/Cargo.toml
+++ b/crates/integration/Cargo.toml
@@ -18,3 +18,5 @@ era-compiler-llvm-context = { path = "../llvm-context" }
 
 [dev-dependencies]
 sha1 = { workspace = true }
+serde = { workspace = true }
+serde_json = { workspace = true }
diff --git a/crates/integration/codesize.json b/crates/integration/codesize.json
new file mode 100644
index 0000000..2c017e8
--- /dev/null
+++ b/crates/integration/codesize.json
@@ -0,0 +1,5 @@
+{
+  "Baseline": 3551,
+  "Computation": 5912,
+  "Fibonacci": 4909
+}
\ No newline at end of file
diff --git a/crates/integration/src/cases.rs b/crates/integration/src/cases.rs
index ca95ed7..47ff03b 100644
--- a/crates/integration/src/cases.rs
+++ b/crates/integration/src/cases.rs
@@ -117,3 +117,52 @@ impl Contract {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use serde::{de::Deserialize, Serialize};
+    use std::{collections::HashMap, fs::File};
+
+    use super::Contract;
+
+    #[test]
+    fn codesize() {
+        let path = "codesize.json";
+
+        let existing = File::open(path)
+            .map(|file| {
+                HashMap::<String, usize>::deserialize(&mut serde_json::Deserializer::from_reader(
+                    file,
+                ))
+                .expect("should be able to deserialze codesize data")
+            })
+            .ok();
+
+        let sizes = HashMap::from([
+            ("Baseline", Contract::baseline().pvm_runtime.len()),
+            ("Computation", Contract::odd_product(0).pvm_runtime.len()),
+            ("Fibonacci", Contract::fib_iterative(0).pvm_runtime.len()),
+        ]);
+
+        for (name, bytes) in sizes.iter() {
+            let change = existing
+                .as_ref()
+                .and_then(|map| map.get(*name))
+                .map(|old| {
+                    let new = *bytes as f32;
+                    let old = *old as f32;
+                    let p = (new - old) / new * 100.0;
+                    format!("({p}% change from {old} bytes)")
+                })
+                .unwrap_or_else(String::new);
+
+            println!("{name}: {bytes} bytes {change}");
+        }
+
+        sizes
+            .serialize(&mut serde_json::Serializer::pretty(
+                File::create(path).unwrap(),
+            ))
+            .unwrap_or_else(|err| panic!("can not write codesize data to '{}': {}", path, err));
+    }
+}
diff --git a/crates/llvm-context/Cargo.toml b/crates/llvm-context/Cargo.toml
index a740dc2..7abe6b5 100644
--- a/crates/llvm-context/Cargo.toml
+++ b/crates/llvm-context/Cargo.toml
@@ -12,6 +12,9 @@ description = "Shared front end code of the EraVM compilers"
 [lib]
 doctest = false
 
+[features]
+riscv-zbb = []
+
 [dependencies]
 anyhow = { workspace = true }
 semver = { workspace = true }
diff --git a/crates/llvm-context/src/target_machine/mod.rs b/crates/llvm-context/src/target_machine/mod.rs
index 8790a7b..2ed67fb 100644
--- a/crates/llvm-context/src/target_machine/mod.rs
+++ b/crates/llvm-context/src/target_machine/mod.rs
@@ -29,6 +29,12 @@ impl TargetMachine {
     /// The LLVM target triple.
     pub const VM_TARGET_TRIPLE: &'static str = "riscv32-unknown-unknown-elf";
 
+    /// LLVM target features.
+    #[cfg(feature = "riscv-zbb")]
+    pub const VM_FEATURES: &'static str = "+zbb,+e,+m";
+    #[cfg(not(feature = "riscv-zbb"))]
+    pub const VM_FEATURES: &'static str = "+e,+m";
+
     ///
     /// A shortcut constructor.
     ///
@@ -40,7 +46,7 @@ impl TargetMachine {
             .create_target_machine(
                 &inkwell::targets::TargetTriple::create(target.triple()),
                 "generic-rv32",
-                "+e,+m",
+                Self::VM_FEATURES,
                 optimizer_settings.level_back_end,
                 inkwell::targets::RelocMode::PIC,
                 inkwell::targets::CodeModel::Default,