Cleanup/optimize the use of references vs clones when peeking, pushin…

…g, updating values on stack, as well as jumping to labels in the activation.

10%ish improvement in tight loop benches when a lot of those kinds of operations are performed.

crates/kernel/src/builtins/bf_objects.rs

@@ -452,7 +452,7 @@ async fn bf_move<'a>(bf_args: &mut BfCallState<'a>) -> Result<BfRet, Error> {
                 // Accept verb has been called, and returned. Check the result. Should be on stack,
                 // unless short-circuited, in which case we assume *false*
                 let result = if !shortcircuit {
-                    bf_args.exec_state.top().peek_top().unwrap()
+                    bf_args.exec_state.top().peek_top().unwrap().clone()
                 } else {
                     v_int(0)
                 };

crates/kernel/src/vm/activation.rs

@@ -321,9 +321,9 @@ impl Activation {
     #[inline]
     pub fn next_op(&mut self) -> Op {
         assert!(self.pc < self.program.main_vector.len(), "pc out of bounds");
-        let op = self.program.main_vector[self.pc].clone();
+        let op = &self.program.main_vector[self.pc];
         self.pc += 1;
-        op
+        op.clone()
     }
 
     #[inline]
@@ -347,8 +347,8 @@ impl Activation {
     }
 
     #[inline]
-    pub fn peek_top(&self) -> Option<Var> {
-        self.valstack.last().cloned()
+    pub fn peek_top(&self) -> Option<&Var> {
+        self.valstack.last()
     }
 
     #[inline]
@@ -363,10 +363,10 @@ impl Activation {
     }
 
     #[inline]
-    pub fn peek2(&self) -> (Var, Var) {
+    pub fn peek2(&self) -> (&Var, &Var) {
         let l = self.valstack.len();
         let (a, b) = (&self.valstack[l - 1], &self.valstack[l - 2]);
-        (a.clone(), b.clone())
+        (a, b)
     }
 
     #[inline]
@@ -376,7 +376,7 @@ impl Activation {
     }
 
     #[inline]
-    pub fn jump(&mut self, label_id: Label) {
+    pub fn jump(&mut self, label_id: &Label) {
         let label = &self.program.jump_labels[label_id.0 as usize];
         self.pc = label.position.0;
     }

crates/kernel/src/vm/exec_state.rs

@@ -147,8 +147,8 @@ impl VMExecState {
 
     /// Push a value onto the value stack
     #[inline]
-    pub(crate) fn push(&mut self, v: &Var) {
-        self.top_mut().push(v.clone())
+    pub(crate) fn push(&mut self, v: Var) {
+        self.top_mut().push(v)
     }
 
     /// Non-destructively peek a range of values from the value stack.
@@ -168,19 +168,19 @@ impl VMExecState {
 
     /// Return the top two values on the value stack.
     #[inline]
-    pub(crate) fn peek2(&self) -> (Var, Var) {
+    pub(crate) fn peek2(&self) -> (&Var, &Var) {
         self.top().peek2()
     }
 
     /// Update at a set offset in the value stack.
     #[inline]
-    pub(crate) fn update(&mut self, amt: usize, v: &Var) {
-        self.top_mut().update(amt, v.clone())
+    pub(crate) fn update(&mut self, amt: usize, v: Var) {
+        self.top_mut().update(amt, v)
     }
 
     /// Return the top of the value stack.
     #[inline]
-    pub(crate) fn peek_top(&self) -> Var {
+    pub(crate) fn peek_top(&self) -> &Var {
         self.top().peek_top().expect("stack underflow")
     }
 
@@ -192,19 +192,19 @@ impl VMExecState {
 
     /// Jump to the given label.
     #[inline]
-    pub(crate) fn jump(&mut self, label: Label) {
+    pub(crate) fn jump(&mut self, label: &Label) {
         self.top_mut().jump(label)
     }
 
     /// Return the value of a local variable.
     #[inline]
-    pub(crate) fn get_env(&self, id: Name) -> Option<&Var> {
+    pub(crate) fn get_env(&self, id: &Name) -> Option<&Var> {
         self.top().environment.get(id.0 as usize)
     }
 
     /// Set the value of a local variable.
     #[inline]
-    pub(crate) fn set_env(&mut self, id: Name, v: &Var) {
+    pub(crate) fn set_env(&mut self, id: &Name, v: Var) {
         self.top_mut().environment.set(id.0 as usize, v.clone());
     }
 }