Added CALL and call extern fn example

1 files changed, 30 insertions, 0 deletions

diff --git a/examples/add.rs b/examples/add.rs
new file mode 100644
index 0000000..ef010b6
--- /dev/null
+++ b/examples/add.rs
@@ -0,0 +1,30 @@
+use juicebox_asm::prelude::*;
+use juicebox_asm::Runtime;
+use Reg64::*;
+
+extern "C" fn add(a: u32, b: u32) -> u32 {
+    a + b
+}
+
+fn main() {
+    let mut asm = Asm::new();
+
+    // SystemV abi:
+    //   rdi -> first argument
+    //   rsi -> second argument
+    //   rax -> return value
+    //
+    asm.mov(rsi, Imm64::from(42));
+    asm.mov(rax, Imm64::from(add as u64));
+    asm.call(rax);
+    asm.ret();
+
+    let code = asm.into_code();
+    std::fs::write("jit.asm", &code).unwrap();
+
+    let rt = Runtime::new(&code);
+    let add42 = unsafe { rt.as_fn::<extern "C" fn(u32) -> u32>() };
+
+    let res = add42(5);
+    assert_eq!(res, 47);
+}