Promotion Heurisitcs (subsumes #1750) (#1758)

* first attempt

* added test cases

* clippy

* comments

* no loop setting

* compile repeat better

* rewrite tests

* support invokes

* style

* clippy

* small change

calyx-ir/src/control.rs

@@ -589,6 +589,17 @@ impl Control {
         let empty = Control::empty();
         std::mem::replace(self, empty)
     }
+
+    /// Replaces &mut self with an empty control statement, and returns StaticControl
+    /// of self. Note that this only works on Control that is static
+    pub fn take_static_control(&mut self) -> StaticControl {
+        let empty = Control::empty();
+        let control = std::mem::replace(self, empty);
+        let Control::Static(static_control) = control  else {
+            unreachable!("Called take_static_control on non-static control")
+        };
+        static_control
+    }
 }
 
 impl StaticControl {

calyx-opt/src/passes/compile_repeat.rs

@@ -66,6 +66,10 @@ impl Visitor for CompileRepeat {
             )
             .to_vec();
             init_group.borrow_mut().assignments = init_assigns;
+            init_group
+                .borrow_mut()
+                .attributes
+                .insert(ir::NumAttr::PromoteStatic, 1);
             // incr_group:
             // 1) writes results of idx + 1 into idx (i.e., increments idx)
             // 2) writes the result of (idx + 1 < num_repeats) into cond_reg,
@@ -84,6 +88,10 @@ impl Visitor for CompileRepeat {
             )
             .to_vec();
             incr_group.borrow_mut().assignments = idx_incr_assigns;
+            incr_group
+                .borrow_mut()
+                .attributes
+                .insert(ir::NumAttr::PromoteStatic, 1);
             // create control:
             // init_group; while cond_reg.out {repeat_body; incr_group;}
             let while_body = ir::Control::seq(vec![