Demonstrate arguments, returns, and adds in example

lib/simplejit/examples/simplejit-minimal.rs

@@ -11,24 +11,40 @@ fn main() {
     let mut module: Module<SimpleJITBackend> = Module::new(SimpleJITBuilder::new());
     let mut ctx = module.make_context();
     let mut func_ctx = FunctionBuilderContext::new();
-    let sig = module.make_signature();
 
-    let func_a = module.declare_function("a", Linkage::Local, &sig).unwrap();
-    let func_b = module.declare_function("b", Linkage::Local, &sig).unwrap();
+    let mut sig_a = module.make_signature();
+    sig_a.params.push(AbiParam::new(types::I32));
+    sig_a.returns.push(AbiParam::new(types::I32));
 
+    let mut sig_b = module.make_signature();
+    sig_b.returns.push(AbiParam::new(types::I32));
+
+    let func_a = module
+        .declare_function("a", Linkage::Local, &sig_a)
+        .unwrap();
+    let func_b = module
+        .declare_function("b", Linkage::Local, &sig_b)
+        .unwrap();
+
+    ctx.func.signature = sig_a;
     ctx.func.name = ExternalName::user(0, func_a.index() as u32);
     {
         let mut bcx: FunctionBuilder = FunctionBuilder::new(&mut ctx.func, &mut func_ctx);
         let ebb = bcx.create_ebb();
 
         bcx.switch_to_block(ebb);
-        bcx.ins().return_(&[]);
+        bcx.append_ebb_params_for_function_params(ebb);
+        let param = bcx.ebb_params(ebb)[0];
+        let cst = bcx.ins().iconst(types::I32, 37);
+        let add = bcx.ins().iadd(cst, param);
+        bcx.ins().return_(&[add]);
         bcx.seal_all_blocks();
         bcx.finalize();
     }
     module.define_function(func_a, &mut ctx).unwrap();
     module.clear_context(&mut ctx);
 
+    ctx.func.signature = sig_b;
     ctx.func.name = ExternalName::user(0, func_b.index() as u32);
     {
         let mut bcx: FunctionBuilder = FunctionBuilder::new(&mut ctx.func, &mut func_ctx);
@@ -36,8 +52,14 @@ fn main() {
 
         bcx.switch_to_block(ebb);
         let local_func = module.declare_func_in_func(func_a, &mut bcx.func);
-        bcx.ins().call(local_func, &[]);
-        bcx.ins().return_(&[]);
+        let arg = bcx.ins().iconst(types::I32, 5);
+        let call = bcx.ins().call(local_func, &[arg]);
+        let value = {
+            let results = bcx.inst_results(call);
+            assert_eq!(results.len(), 1);
+            results[0].clone()
+        };
+        bcx.ins().return_(&[value]);
         bcx.seal_all_blocks();
         bcx.finalize();
     }
@@ -51,8 +73,10 @@ fn main() {
     let code_b = module.get_finalized_function(func_b);
 
     // Cast it to a rust function pointer type.
-    let ptr_b = unsafe { mem::transmute::<_, fn()>(code_b) };
+    let ptr_b = unsafe { mem::transmute::<_, fn() -> u32>(code_b) };
 
     // Call it!
-    ptr_b();
+    let res = ptr_b();
+
+    assert_eq!(res, 42);
 }