Improve register reuse

src/compile.rs

@@ -41,6 +41,30 @@ impl LocalCounter {
         }
     }
 
+    pub fn consecutive(&mut self, amount: usize) -> Vec<u16> {
+        'outer: for free_num in self.1.clone() {
+            let mut potentials = vec![free_num];
+            let mut curr = free_num;
+            for _ in 0..amount {
+                if let Some(next) = self.1.iter().find(|v| **v == curr + 1) {
+                    potentials.push(*next);
+                    curr = *next;
+                } else {
+                    continue 'outer;
+                }
+            }
+
+            self.1
+                .retain_mut(|v| potentials.iter().find(|p| v != *p).is_none());
+            return potentials;
+        }
+        let mut returned = Vec::new();
+        for _ in 0..amount {
+            returned.push(self.new());
+        }
+        returned
+    }
+
     pub fn new(&mut self) -> u16 {
         let temp = self.0;
         self.0 += 1;
@@ -453,10 +477,14 @@ impl Expression {
                     original_param_regs.extend(registers);
                 }
 
-                let function_reg = scope.register_counter.new();
+                let mut registers = scope
+                    .register_counter
+                    .consecutive(original_param_regs.len() + 1)
+                    .into_iter();
+                let function_reg = registers.next().unwrap();
                 let mut param_regs = Vec::new();
                 for _ in &original_param_regs {
-                    param_regs.push(scope.register_counter.new());
+                    param_regs.push(registers.next().unwrap());
                 }
 
                 for (i, param_reg) in original_param_regs.iter().enumerate().rev() {