diff --git a/compiler.ts b/compiler.ts
index 8cf72b0..e4c2220 100644
--- a/compiler.ts
+++ b/compiler.ts
@@ -45,20 +45,49 @@ export function functionList(module: string) {
     return result;
 }
 
+/**
+ * CLI options used for llvm-extract executable.
+ */
+export interface ExtractOptions {
+    /**
+     * Functions to extract.
+     */
+    func?: string[]
+
+    /**
+     * Basic block specifiers.
+     */
+    bb?: string[]
+
+    output?: string
+
+    /**
+     * Input file name. If unspecified, llvm-extract reads from stdin
+     */
+    input?: string
+
+    asm?: boolean
+}
+
+export function extractCommand(options: ExtractOptions): string[] {
+    return [
+        ...(options.func ?? []).flatMap(name => ["--func", name]),
+        ...(options.bb ?? []).flatMap(name => ["--bb", name]),
+        ...(options.output ? ["-o", options.output] : []),
+        ...(options.asm ? ["-S"] : []),
+        ...(options.input ? [options.input] : [])
+    ];
+}
+
 
 /**
  * Extract one function using llvm-extract
  */
-export async function extract(name: string, module: string, out: (a: string) => string) {
+export async function extract(options: ExtractOptions) {
     let process = child_process.spawn(
-        LLVM_EXTRACT, [
-        "--func",
-        name,
-        "-S",
-        "-o",
-        out(name),
-        module
-    ], { stdio: "inherit" }
+        LLVM_EXTRACT,
+        extractCommand(options),
+        { stdio: "inherit" }
     )
     const exitcode = await new Promise((resolve, reject) => { process.on('close', resolve) })
     return exitcode