diff --git a/src/ir/builder.rs b/src/ir/builder.rs
index 17d9593..c804fbe 100644
--- a/src/ir/builder.rs
+++ b/src/ir/builder.rs
@@ -365,6 +365,27 @@ pub trait GlobalValueBuilder: QueryValueData + AddValue + ConstantBuilder {
         let data = FunctionData::new(name, ty.clone(), kind);
         self.add_function(data.new_value_data(), data)
     }
+
+    /// Build a function definition.
+    fn function_def(&mut self, name: String, ty: Type) -> Result<Function, BuilderErr> {
+        let data = FunctionData::new(name, ty.clone(), FunctionKind::Definition);
+        let function = self.add_function(data.new_value_data(), data)?;
+        Ok(function)
+    }
+
+    /// Build a function declaration.
+    fn function_decl(&mut self, name: String, ty: Type) -> Result<Function, BuilderErr> {
+        let data = FunctionData::new(name, ty.clone(), FunctionKind::Declaration);
+        let function = self.add_function(data.new_value_data(), data)?;
+        Ok(function)
+    }
+
+    /// Build a intrinsic function.
+    fn function_intrinsic(&mut self, name: String, ty: Type) -> Result<Function, BuilderErr> {
+        let data = FunctionData::new(name, ty.clone(), FunctionKind::Intrinsic);
+        let function = self.add_function(data.new_value_data(), data)?;
+        Ok(function)
+    }
 }
 
 pub struct LocalBuilder<'a> {
diff --git a/src/main.rs b/src/main.rs
index a4cb240..36df734 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -2,7 +2,6 @@ use std::io;
 
 use ir::{
     builder::{GlobalValueBuilder, LocalBlockBuilder, LocalValueBuilder},
-    entities::FunctionKind,
     module::Module,
     pass::GlobalPass,
     types::Type,
@@ -17,10 +16,9 @@ fn main() -> io::Result<()> {
     let mut module = Module::new("test".to_string());
     let function = module
         .builder()
-        .function(
+        .function_def(
             "test_func".to_string(),
             Type::mk_function(vec![], Type::mk_void()),
-            FunctionKind::Definition,
         )
         .unwrap();