feat: loop validation/execution

Signed-off-by: Cem Onem <[email protected]>

src/execution/interpreter_loop.rs

@@ -118,7 +118,7 @@ pub(super) fn run<H: HookSet>(
                 wasm.read_var_u32().unwrap_validated();
                 do_sidetable_control_transfer(&mut wasm, stack, &mut stp, current_sidetable);
             }
-            BLOCK => {
+            BLOCK | LOOP => {
                 BlockType::read_unvalidated(&mut wasm);
             }
             RETURN => {

src/validation/code.rs

@@ -219,7 +219,12 @@ fn read_instructions(
                 stack.assert_push_ctrl(label_info, block_ty)?;
             }
             LOOP => {
-                todo!("implement loop");
+                let block_ty = BlockType::read(wasm)?.as_func_type(fn_types)?;
+                let label_info = LabelInfo::Loop {
+                    ip: wasm.pc,
+                    stp: sidetable.len(),
+                };
+                stack.assert_push_ctrl(label_info, block_ty)?;
             }
             IF => {
                 todo!("implement if");
@@ -259,9 +264,7 @@ fn read_instructions(
                     LabelInfo::If { .. } => {
                         todo!("implement if");
                     }
-                    LabelInfo::Loop { .. } => {
-                        todo!("implement loop");
-                    }
+                    LabelInfo::Loop { .. } => (),
                     LabelInfo::Func { stps_to_backpatch } => {
                         // same as blocks, except jump just before the end instr, not after it
                         // the last end instruction will handle the return to callee during execution

tests/structured_control_flow/loop.rs

@@ -1 +1,70 @@
+use wasm::{validate, RuntimeInstance};
 
+const FIBONACCI_WITH_LOOP_AND_BR_IF: &str = r#"
+(module
+  (func $fibonacci (param $n i32) (result i32)
+    (local $prev i32)
+    (local $curr i32)
+    (local $counter i32)
+
+    i32.const 0
+    local.set $prev
+    i32.const 1
+    local.set $curr
+
+    local.get $n
+    i32.const 1
+    i32.add
+    local.set $counter
+
+    block $exit
+      loop $loop
+        local.get $counter
+        i32.const 1
+        i32.le_s
+        br_if $exit
+
+        local.get $curr
+        local.get $curr
+        local.get $prev
+        i32.add
+        local.set $curr
+        local.set $prev
+
+        local.get $counter
+        i32.const 1
+        i32.sub
+        local.set $counter
+
+        br $loop
+
+        drop
+        drop
+        drop
+
+      end $loop
+    end $exit
+
+    local.get $curr
+  )
+
+  (export "fibonacci" (func $fibonacci))
+)"#;
+
+#[test_log::test]
+fn fibonacci_with_loop_and_br_if() {
+    let wasm_bytes = wat::parse_str(FIBONACCI_WITH_LOOP_AND_BR_IF).unwrap();
+
+    let validation_info = validate(&wasm_bytes).expect("validation failed");
+    let mut instance = RuntimeInstance::new(&validation_info).expect("instantiation failed");
+
+    let fibonacci_fn = instance.get_function_by_index(0, 0).unwrap();
+
+    assert_eq!(1, instance.invoke(&fibonacci_fn, -5).unwrap());
+    assert_eq!(1, instance.invoke(&fibonacci_fn, 0).unwrap());
+    assert_eq!(1, instance.invoke(&fibonacci_fn, 1).unwrap());
+    assert_eq!(2, instance.invoke(&fibonacci_fn, 2).unwrap());
+    assert_eq!(3, instance.invoke(&fibonacci_fn, 3).unwrap());
+    assert_eq!(5, instance.invoke(&fibonacci_fn, 4).unwrap());
+    assert_eq!(8, instance.invoke(&fibonacci_fn, 5).unwrap());
+}