WIP optimization code

rust_compiler/libs/optimizer/src/leaf_function.rs

@@ -0,0 +1,44 @@
+use il::{Instruction, InstructionNode};
+use std::collections::HashSet;
+
+/// Scans the instruction set to identify "leaf functions".
+/// A leaf function is defined as a function (delimited by LabelDefs) that does not
+/// contain any `jal` (JumpAndLink) instructions.
+///
+/// Returns a Set containing the names of all identified leaf functions.
+pub fn find_leaf_functions(instructions: &[InstructionNode]) -> HashSet<String> {
+    let mut leaf_functions = HashSet::new();
+    let mut current_label: Option<String> = None;
+    let mut is_current_leaf = true;
+
+    for node in instructions {
+        match &node.instruction {
+            Instruction::LabelDef(label) => {
+                // If we were tracking a function, and it remained a leaf until now, save it.
+                if let Some(name) = current_label.take()
+                    && is_current_leaf
+                {
+                    leaf_functions.insert(name);
+                }
+
+                // Start tracking the new function
+                current_label = Some(label.to_string());
+                is_current_leaf = true;
+            }
+            Instruction::JumpAndLink(_) => {
+                // If we see a JAL, this function is NOT a leaf.
+                is_current_leaf = false;
+            }
+            _ => {}
+        }
+    }
+
+    // Handle the final function in the file
+    if let Some(name) = current_label
+        && is_current_leaf
+    {
+        leaf_functions.insert(name);
+    }
+
+    leaf_functions
+}