diff --git a/src/frontend.rs b/src/frontend.rs
index 55ad308..29436b3 100644
--- a/src/frontend.rs
+++ b/src/frontend.rs
@@ -4,7 +4,7 @@ use std::fmt::Write;
 
 use super::parser;
 use crate::rtlil;
-pub use callable::{Callable, CallableId};
+pub use callable::{Callable, CallableContext, CallableId};
 pub use types::{Type, TypeStruct, TypingContext};
 
 mod callable;
@@ -65,7 +65,7 @@ impl Signal {
 pub struct Context {
     /// map callable name to callable
     callable_names: BTreeMap<String, CallableId>,
-    callables: BTreeMap<CallableId, Callable>,
+    callables: CallableContext,
     /// type names
     typenames: BTreeMap<String, Type>,
     types: TypingContext,
@@ -90,17 +90,23 @@ impl Counter {
 
 impl Context {
     pub fn new() -> Self {
-        let tcx = TypingContext::new();
+        let mut tcx = TypingContext::new();
+        let ccx = CallableContext::new(&mut tcx);
+
+        let typenames = [
+            ("Logic".to_string(), tcx.primitives.logic),
+            ("Num".to_string(), tcx.primitives.elabnum),
+        ]
+        .into();
+
+        let callable_names = [("reduce_or".to_string(), ccx.builtins.reduce_or)].into();
+
         Context {
-            callables: BTreeMap::new(),
-            callable_names: BTreeMap::new(),
+            callables: ccx,
+            callable_names,
             signals: BTreeMap::new(),
-            types: TypingContext::new(),
-            typenames: [
-                ("Logic".to_string(), tcx.primitives.logic),
-                ("Num".to_string(), tcx.primitives.elabnum),
-            ]
-            .into(),
+            types: tcx,
+            typenames,
             ids: Counter::new(),
         }
     }
@@ -166,7 +172,7 @@ impl Context {
                 typed_ir::Expr {
                     id,
                     kind: typed_ir::ExprKind::Call {
-                        called: typed_ir::DefId(99),
+                        called: self.callables.builtins.bitnot,
                         args: vec![a],
                     },
                     typ: self.types.primitives.infer,
@@ -177,7 +183,7 @@ impl Context {
                 typed_ir::Expr {
                     id,
                     kind: typed_ir::ExprKind::Call {
-                        called: typed_ir::DefId(99),
+                        called: self.callables.builtins.xor,
                         args: vec![a, b],
                     },
                     typ: self.types.primitives.infer,
@@ -189,10 +195,11 @@ impl Context {
                     .iter()
                     .map(|expr| self.type_expression(expr))
                     .collect::<Result<Vec<_>, _>>()?;
+                let called = self.try_get_callable(call.name.fragment())?;
                 typed_ir::Expr {
                     id,
                     kind: typed_ir::ExprKind::Call {
-                        called: typed_ir::DefId(99),
+                        called,
                         args: args_resolved,
                     },
                     typ: self.types.primitives.infer,
@@ -286,7 +293,8 @@ impl Context {
                         Ok(format!("_{}", arg.id.0))
                     })
                     .collect::<Result<Vec<_>, std::fmt::Error>>()?;
-                format!("_{}({})", called.0, args.join(", "))
+                let callable = self.callables.get(*called);
+                format!("{}({})", callable.name(), args.join(", "))
             }
         };
         let mut type_pretty = String::new();
diff --git a/src/frontend/callable.rs b/src/frontend/callable.rs
index f81ed33..5025419 100644
--- a/src/frontend/callable.rs
+++ b/src/frontend/callable.rs
@@ -1,7 +1,8 @@
-use super::types::Type;
+use super::types::{Type, TypingContext};
+use std::collections::HashMap;
 
-#[derive(Copy, Clone, PartialEq)]
-pub struct CallableId(u32);
+#[derive(Debug, Copy, Clone, PartialOrd, PartialEq, Eq, Ord)]
+pub struct CallableId(pub usize);
 
 pub struct Callable {
     pub name: String,
@@ -18,3 +19,54 @@ impl<'ty> Callable {
         self.args.len()
     }
 }
+
+pub struct BuiltinCallables {
+    pub xor: CallableId,
+    pub bitnot: CallableId,
+    pub reduce_or: CallableId,
+}
+
+pub struct CallableContext {
+    pub builtins: BuiltinCallables,
+    callables: Vec<Callable>,
+}
+
+impl CallableContext {
+    pub fn new(typectx: &mut TypingContext) -> Self {
+        let builtins = BuiltinCallables {
+            xor: CallableId(0),
+            bitnot: CallableId(1),
+            reduce_or: CallableId(2),
+        };
+        Self {
+            callables: vec![
+                Callable {
+                    name: "builtin::xor".to_string(),
+                    args: vec![],
+                    ret_type: Some(typectx.primitives.logic),
+                },
+                Callable {
+                    name: "builtin::bitnot".to_string(),
+                    args: vec![],
+                    ret_type: Some(typectx.primitives.logic),
+                },
+                Callable {
+                    name: "builtin::reduce_or".to_string(),
+                    args: vec![],
+                    ret_type: Some(typectx.primitives.logic),
+                },
+            ],
+            builtins,
+        }
+    }
+
+    pub fn add(&mut self, callable: Callable) -> CallableId {
+        let id = self.callables.len();
+        self.callables.push(callable);
+        CallableId(id)
+    }
+
+    pub fn get(&self, id: CallableId) -> &Callable {
+        &self.callables[id.0]
+    }
+}
diff --git a/src/frontend/typed_ir.rs b/src/frontend/typed_ir.rs
index 8bcc635..77b0d88 100644
--- a/src/frontend/typed_ir.rs
+++ b/src/frontend/typed_ir.rs
@@ -1,3 +1,4 @@
+use super::callable::CallableId;
 use super::types::{ElabData, Type};
 use std::fmt::Debug;
 
@@ -31,7 +32,7 @@ pub struct Expr {
 pub enum ExprKind {
     Literal(ElabData),
     Path(DefId),
-    Call { called: DefId, args: Vec<Expr> },
+    Call { called: CallableId, args: Vec<Expr> },
 }
 
 #[derive(Debug, Clone)]
diff --git a/src/frontend/types.rs b/src/frontend/types.rs
index 4c05b83..cef1dc3 100644
--- a/src/frontend/types.rs
+++ b/src/frontend/types.rs
@@ -27,11 +27,17 @@ enum TypeKind {
     /// UInt of generic width
     UInt(ElabData),
     /// Callable
-    Callable,
+    Callable(FnSig),
     /// A type that was not given and needs to be inferred
     Infer,
 }
 
+#[derive(Debug, Clone)]
+pub struct FnSig {
+    params: Vec<Type>,
+    ret: Type,
+}
+
 #[derive(Debug, Clone)]
 pub struct ElabData {
     typ: Type,
@@ -145,7 +151,7 @@ impl TypingContext {
                 }
             }
             TypeKind::UInt(_) => todo!(),
-            TypeKind::Callable => todo!("callable generic params"),
+            TypeKind::Callable(_sig) => todo!("callable generic params"),
             // need to know what the type is to parameterize it
             TypeKind::Infer => None,
         }
@@ -172,7 +178,7 @@ impl TypingContext {
             }
             TypeKind::Infer => write!(w, "?"),
             TypeKind::UInt(_) => todo!("print uint"),
-            TypeKind::Callable => todo!("print callable"),
+            TypeKind::Callable(_sig) => todo!("print callable"),
         }
     }
 }