.gitignore

@@ -1,2 +1,4 @@
 /target
-**/*.env
+**/*.env
+Cargo.lock
+*Cargo.lock

c_compiler/code.c

@@ -1,6 +1,4 @@
-int x = 5;
-
-int add(int a, int b) { return a + b; }
+int var_x = 5;
 
 int factorial(int n) {
   if (n <= 1) {
@@ -10,12 +8,7 @@ int factorial(int n) {
 }
 
 int main() {
-  int x;
-  x = 5;
-  int x = 5;
-  int result;
-  int result = 5;
-  result = x + factorial(5);
+  int result = var_x + factorial(5);
   print(result);
   return 0;
 }

c_compiler/src/codegen.rs

@@ -1,17 +1,25 @@
+use std::hash::Hash;
+use std::sync::atomic::AtomicU32;
 use std::time::SystemTime;
 use std::{collections::HashMap, path::PathBuf};
 
 use chrono::{DateTime, Local};
 
+use crate::registers::RegisterAllocator;
 use crate::{block, cmd, comment, dsa};
 
-use crate::parser::{ConstExpr, Declaration, Program};
+use crate::parser::{
+    BinaryOperator, ConstExpr, Declaration, Expression, Parameter, Program, Statement,
+    UnaryOperator,
+};
 
 pub struct CodeGenerator {
     ast: Program,
     imports: HashMap<String, String>,
     globals: Vec<String>,
     functions: Vec<String>,
+    allocator: RegisterAllocator,
+    call_stack: Vec<String>,
 }
 
 fn import(name: &str, path: &str) -> String {
@@ -25,6 +33,8 @@ impl CodeGenerator {
             imports: HashMap::new(),
             globals: Vec::new(),
             functions: Vec::new(),
+            allocator: RegisterAllocator::new(),
+            call_stack: Vec::new(),
         }
     }
 
@@ -37,44 +47,16 @@ impl CodeGenerator {
         self.include("print", "./lib/io/print.dsa");
 
         for block in self.ast.clone().declarations {
-            self.generate_block(block.clone());
+            self.generate_block(block.clone())?;
+        }
+
+        for func in &self.functions {
+            println!("{func}");
         }
 
         self.generate_layout()
     }
 
-    fn generate_block(&mut self, block: Declaration) {
-        match block {
-            Declaration::Variable { name, init } => self.globals.push(format!(
-                "dw {}: {}",
-                name,
-                init.unwrap_or(ConstExpr::Number(0))
-            )),
-            Declaration::Function {
-                name,
-                return_type,
-                params,
-                body,
-            } => {
-                let function_start = format!(
-                    "{name}: \n\t\
-                    push bpr \n\t\
-                    mov spr, bpr"
-                );
-
-                let function_end = format!(
-                    "\n\t\
-                    mov bpr, spr \n\t\
-                    pop bpr \n\t\
-                    return\n"
-                );
-
-                self.functions
-                    .push(format!("{function_start}\n{function_end}"));
-            }
-        }
-    }
-
     fn generate_layout(&mut self) -> Result<String, String> {
         let datetime: DateTime<Local> = SystemTime::now().into();
         Ok(dsa![
@@ -114,19 +96,416 @@ impl CodeGenerator {
                 dsa![pop zero],
                 dsa![hlt]
             ],
-            block! [ "main"
-                dsa![push bpr],
-                dsa![mov spr, bpr],
-                dsa![lwi 67, rg1],
-                dsa![stw rg1, spr, 8],
-                dsa![mov bpr, spr],
-                dsa![pop bpr],
-                dsa![return]
-            ],
+            // block! [ "main"
+            //     dsa![push bpr],
+            //     dsa![mov spr, bpr],
+            //     dsa![lwi 67, rg1],
+            //     dsa![stw rg1, spr, 8],
+            //     dsa![mov bpr, spr],
+            //     dsa![pop bpr],
+            //     dsa![return]
+            // ],
             "",
             self.functions.join("\n"),
         ])
     }
+
+    fn generate_global(&mut self, name: &str, init: Option<ConstExpr>) {
+        self.globals.push(format!(
+            "dw {}: {}",
+            name,
+            init.unwrap_or(ConstExpr::Number(0))
+        ))
+    }
+
+    fn generate_block(&mut self, block: Declaration) -> Result<(), String> {
+        match block {
+            Declaration::Variable { name, init } => self.generate_global(&name, init),
+            Declaration::Function {
+                name,
+                return_type,
+                params,
+                body,
+            } => {
+                let func = self.generate_function(&name, &params, &body).join("\n");
+
+                self.functions.push(format!("{func}\n"));
+            }
+        };
+
+        Ok(())
+    }
+
+    // Example: Generate code for a function
+    fn generate_function(
+        &mut self,
+        name: &str,
+        params: &[Parameter],
+        body: &[Statement],
+    ) -> Vec<String> {
+        self.call_stack.push(name.to_string());
+
+        let mut code = Vec::new();
+
+        // Reset allocator for new function
+        self.allocator.reset();
+
+        // Function prologue
+        code.push(format!("{}:", name));
+        code.push("\tpush bpr".to_string());
+        code.push("\tmov spr, bpr".to_string());
+
+        // Allocate parameters to registers or stack locations
+        for (i, param) in params.iter().enumerate() {
+            let offset = 8 + (i as i32 * 4); // Parameters start at bpr+8
+            // Track that this parameter is at a stack location
+            let (reg, mut load_code) = self.allocator.alloc_var(&param.name).unwrap();
+            code.extend(load_code);
+            code.push(format!("\tldw bpr, {}, {}", reg, offset));
+        }
+
+        // Generate code for function body
+        for stmt in body {
+            let stmt_code = self.generate_statement(stmt).unwrap();
+            code.extend(stmt_code);
+        }
+
+        // Function epilogue
+        code.push(format!("_ret_{name}:"));
+        code.push("\tmov bpr, spr".to_string());
+        code.push("\tpop bpr".to_string());
+        code.push("\treturn".to_string());
+
+        self.call_stack.pop();
+        code
+    }
+
+    // Example: Generate code for a statement
+    fn generate_statement(&mut self, stmt: &Statement) -> Result<Vec<String>, String> {
+        let mut code = Vec::new();
+
+        match stmt {
+            Statement::Assign {
+                name,
+                declare_type,
+                value,
+            } => {
+                if let Some(expr) = value {
+                    // Evaluate expression
+                    let (result_reg, expr_code) = self.generate_expression(expr)?;
+                    code.extend(expr_code);
+
+                    // Store result in variable
+                    let store_code = self.allocator.store_var(name, &result_reg);
+                    code.extend(store_code);
+
+                    // Free temporary register
+                    self.allocator.free_temp(&result_reg);
+                } else {
+                    // Just declaring variable without initialization
+                    self.allocator.alloc_var(name)?;
+                }
+            }
+
+            Statement::Return { expr } => {
+                if let Some(e) = expr {
+                    let (result_reg, expr_code) = self.generate_expression(e)?;
+                    code.extend(expr_code);
+                    code.push(format!("\tstw {}, bpr, 8", result_reg));
+                    code.push(format!("\tjmp _ret_{}", self.call_stack.last().unwrap()));
+                    self.allocator.free_temp(&result_reg);
+                }
+            }
+
+            Statement::If {
+                condition,
+                then_stmt,
+                else_stmt,
+            } => {
+                // Generate condition
+                let (cond_reg, cond_code) = self.generate_expression(condition)?;
+                code.extend(cond_code);
+
+                // Compare with zero
+                code.push(format!("\tcmp {}, zero", cond_reg));
+                self.allocator.free_temp(&cond_reg);
+
+                // Generate unique labels
+                let then_label = format!("_then_{}", self.get_unique_label());
+                let else_label = format!("_else_{}", self.get_unique_label());
+                let end_label = format!("_end_{}", self.get_unique_label());
+
+                // Jump to else if condition is false (equal to zero)
+                code.push(format!("\tjeq {}", else_label));
+
+                // Then block
+                code.push(format!("{}:", then_label));
+                for s in then_stmt {
+                    code.extend(self.generate_statement(s)?);
+                }
+
+                if then_stmt.len() == 0 {
+                    code.push("\tnop".to_string());
+                }
+
+                code.push(format!("\tjmp {}", end_label));
+
+                // Else block
+                code.push(format!("{}:", else_label));
+                for s in else_stmt {
+                    code.extend(self.generate_statement(s)?);
+                }
+
+                if else_stmt.len() == 0 {
+                    code.push("\tnop".to_string());
+                }
+
+                code.push(format!("{}:", end_label));
+            }
+
+            Statement::While { condition, body } => {
+                let loop_start = format!("_while_start_{}", self.get_unique_label());
+                let loop_end = format!("_while_end_{}", self.get_unique_label());
+
+                code.push(format!("{}:", loop_start));
+
+                // Generate condition
+                let (cond_reg, cond_code) = self.generate_expression(condition)?;
+                code.extend(cond_code);
+
+                code.push(format!("\tcmp {}, zero", cond_reg));
+                self.allocator.free_temp(&cond_reg);
+
+                code.push(format!("\tjeq {}", loop_end));
+
+                // Loop body
+                for s in body {
+                    code.extend(self.generate_statement(s)?);
+                }
+
+                code.push(format!("\tjmp {}", loop_start));
+                code.push(format!("{}:", loop_end));
+            }
+
+            Statement::Expression { expr } => {
+                let (result_reg, expr_code) = self.generate_expression(expr)?;
+                code.extend(expr_code);
+                self.allocator.free_temp(&result_reg);
+            }
+
+            Statement::Block(statements) => {
+                for s in statements {
+                    code.extend(self.generate_statement(s)?);
+                }
+            }
+        }
+
+        Ok(code)
+    }
+
+    // Example: Generate code for an expression
+    // Returns (register containing result, assembly code)
+    fn generate_expression(
+        &mut self,
+        expr: &Expression,
+    ) -> Result<(String, Vec<String>), String> {
+        let mut code = Vec::new();
+
+        match expr {
+            Expression::Number { value } => {
+                let (reg, alloc_code) = self.allocator.alloc_temp()?;
+                code.extend(alloc_code);
+
+                // Load immediate value
+                code.push(format!("\tlli {}, {}", value & 0xFFFF, reg));
+                if *value > 0xFFFF || *value < 0 {
+                    code.push(format!("\tlui {}, {}", (value >> 16) & 0xFFFF, reg));
+                }
+
+                Ok((reg, code))
+            }
+
+            Expression::Variable { name, .. } => {
+                let (reg, load_code) = self.allocator.load_var(name)?;
+                code.extend(load_code);
+                Ok((reg, code))
+            }
+
+            Expression::Binary { op, left, right } => {
+                // Evaluate left operand
+                let (left_reg, left_code) = self.generate_expression(left)?;
+                code.extend(left_code);
+
+                // Evaluate right operand
+                let (right_reg, right_code) = self.generate_expression(right)?;
+                code.extend(right_code);
+
+                // Allocate result register
+                let (result_reg, result_alloc) = self.allocator.alloc_temp()?;
+                code.extend(result_alloc);
+
+                // Generate operation
+                match op {
+                    BinaryOperator::Add => {
+                        code.push(format!(
+                            "\tadd {}, {}, {}",
+                            left_reg, right_reg, result_reg
+                        ));
+                    }
+                    BinaryOperator::Sub => {
+                        code.push(format!(
+                            "\tsub {}, {}, {}",
+                            left_reg, right_reg, result_reg
+                        ));
+                    }
+                    BinaryOperator::Mul => {
+                        self.include("maths", "./lib/maths/core.dsa");
+                        // Call multiply function
+                        code.push(format!("\tpush {}", right_reg));
+                        code.push(format!("\tpush {}", left_reg));
+                        code.push("\tcall maths::multiply".to_string());
+                        code.push(format!("\tpop {}", result_reg));
+                        code.push("\tpop zero".to_string());
+                    }
+                    // Comparison operators - return 1 (true) or 0 (false)
+                    BinaryOperator::Eq => {
+                        code.push(format!("\tcmp {}, {}", left_reg, right_reg));
+                        code.push(format!("\tlli 0, {}", result_reg));
+                        let end_label = format!("_cmp_end_{}", self.get_unique_label());
+                        code.push(format!("\tjne {}", end_label)); // If not equal, skip setting to 1
+                        code.push(format!("\tlli 1, {}", result_reg));
+                        code.push(format!("{}:", end_label));
+                    }
+                    BinaryOperator::Ne => {
+                        code.push(format!("\tcmp {}, {}", left_reg, right_reg));
+                        code.push(format!("\tlli 0, {}", result_reg));
+                        let end_label = format!("_cmp_end_{}", self.get_unique_label());
+                        code.push(format!("\tjeq {}", end_label)); // If equal, skip setting to 1
+                        code.push(format!("\tlli 1, {}", result_reg));
+                        code.push(format!("{}:", end_label));
+                    }
+                    BinaryOperator::Lt => {
+                        code.push(format!("\tcmp {}, {}", left_reg, right_reg));
+                        code.push(format!("\tlli 0, {}", result_reg));
+                        let end_label = format!("_cmp_end_{}", self.get_unique_label());
+                        code.push(format!("\tjge {}", end_label)); // If greater or equal, skip setting to 1
+                        code.push(format!("\tlli 1, {}", result_reg));
+                        code.push(format!("{}:", end_label));
+                    }
+                    BinaryOperator::Le => {
+                        code.push(format!("\tcmp {}, {}", left_reg, right_reg));
+                        code.push(format!("\tlli 0, {}", result_reg));
+                        let end_label = format!("_cmp_end_{}", self.get_unique_label());
+                        code.push(format!("\tjgt {}", end_label)); // If greater than, skip setting to 1
+                        code.push(format!("\tlli 1, {}", result_reg));
+                        code.push(format!("{}:", end_label));
+                    }
+                    BinaryOperator::Gt => {
+                        code.push(format!("\tcmp {}, {}", left_reg, right_reg));
+                        code.push(format!("\tlli 0, {}", result_reg));
+                        let end_label = format!("_cmp_end_{}", self.get_unique_label());
+                        code.push(format!("\tjle {}", end_label)); // If less or equal, skip setting to 1
+                        code.push(format!("\tlli 1, {}", result_reg));
+                        code.push(format!("{}:", end_label));
+                    }
+                    BinaryOperator::Ge => {
+                        code.push(format!("\tcmp {}, {}", left_reg, right_reg));
+                        code.push(format!("\tlli 0, {}", result_reg));
+                        let end_label = format!("_cmp_end_{}", self.get_unique_label());
+                        code.push(format!("\tjlt {}", end_label)); // If less than, skip setting to 1
+                        code.push(format!("\tlli 1, {}", result_reg));
+                        code.push(format!("{}:", end_label));
+                    }
+                    _ => return Err(format!("Unsupported binary operator: {:?}", op)),
+                }
+
+                // Free operand registers
+                self.allocator.free_temp(&left_reg);
+                self.allocator.free_temp(&right_reg);
+
+                Ok((result_reg, code))
+            }
+
+            Expression::Call { name, args } => {
+                // Save caller-saved registers
+                let save_code = self.allocator.save_caller_saved();
+                code.extend(save_code);
+
+                // Evaluate and push arguments in reverse order
+                let mut arg_regs = Vec::new();
+                for arg in args.iter().rev() {
+                    let (arg_reg, arg_code) = self.generate_expression(arg)?;
+                    code.extend(arg_code);
+                    code.push(format!("\tpush {}", arg_reg));
+                    arg_regs.push(arg_reg);
+                }
+
+                if self.functions.contains_key(name) {
+                    // Call local function
+                    code.push(format!("\tcall {}", name));
+                }
+
+                if self.imports
+
+
+
+                // Clean up arguments
+                for _ in 0..args.len() {
+                    code.push("\tpop zero".to_string());
+                }
+
+                // Free argument registers
+                for reg in arg_regs {
+                    self.allocator.free_temp(&reg);
+                }
+
+                // Result is in rg0, allocate a register and move it
+                let (result_reg, result_alloc) = self.allocator.alloc_temp()?;
+                code.extend(result_alloc);
+
+                if result_reg != "rg0" {
+                    code.push(format!("\tmov rg0, {}", result_reg));
+                }
+
+                // Restore caller-saved registers (simplified - you'd track which ones)
+
+                Ok((result_reg, code))
+            }
+
+            Expression::Unary { op, operand } => {
+                let (operand_reg, operand_code) = self.generate_expression(operand)?;
+                code.extend(operand_code);
+
+                let (result_reg, result_alloc) = self.allocator.alloc_temp()?;
+                code.extend(result_alloc);
+
+                match op {
+                    UnaryOperator::Minus => {
+                        // Negate: result = 0 - operand
+                        code.push(format!("\tsub zero, {}, {}", operand_reg, result_reg));
+                    }
+                    UnaryOperator::Plus => {
+                        // Just move
+                        code.push(format!("\tmov {}, {}", operand_reg, result_reg));
+                    }
+                }
+
+                self.allocator.free_temp(&operand_reg);
+                Ok((result_reg, code))
+            }
+
+            Expression::Empty => Ok(("zero".to_string(), code)),
+        }
+    }
+
+    // Helper for generating unique labels
+    fn get_unique_label(&mut self) -> String {
+        // You'd implement a counter here
+        static COUNTER: AtomicU32 = AtomicU32::new(0);
+
+        let val = COUNTER.fetch_add(1, std::sync::atomic::Ordering::SeqCst);
+        (val + 1).to_string()
+    }
 }
 
 /// Build a single string from any number of arguments.

c_compiler/src/main.rs

@@ -5,6 +5,7 @@ use crate::{codegen::CodeGenerator, lexer::Lexer, parser::Parser};
 pub mod codegen;
 pub mod lexer;
 pub mod parser;
+mod registers;
 
 // ============================================================================
 // Main & Tests

c_compiler/src/parser.rs

@@ -17,7 +17,7 @@ pub enum Declaration {
         name: String,
         return_type: Type,
         params: Vec<Parameter>,
-        body: Statement,
+        body: Block,
     },
     Variable {
         name: String,
@@ -44,11 +44,11 @@ pub enum Type {
     Struct(String),
 }
 
+pub type Block = Vec<Statement>;
+
 #[derive(Debug, Clone)]
 pub enum Statement {
-    Compound {
-        statements: Vec<Statement>,
-    },
+    Block(Block),
     Assign {
         // left side
         name: String,
@@ -62,12 +62,12 @@ pub enum Statement {
     },
     If {
         condition: Expression,
-        then_stmt: Box<Statement>,
-        else_stmt: Option<Box<Statement>>,
+        then_stmt: Block,
+        else_stmt: Block,
     },
     While {
         condition: Expression,
-        body: Box<Statement>,
+        body: Vec<Statement>,
     },
     Return {
         expr: Option<Expression>,
@@ -271,7 +271,7 @@ impl Parser {
                 }
 
                 self.expect(TokenType::RParen)?;
-                let body = self.parse_compound_stmt()?;
+                let body = self.parse_block()?;
 
                 Ok(Declaration::Function {
                     name,
@@ -302,7 +302,7 @@ impl Parser {
         }
     }
 
-    fn parse_compound_stmt(&mut self) -> Result<Statement, String> {
+    fn parse_block(&mut self) -> Result<Block, String> {
         self.expect(TokenType::LBrace)?;
         let mut statements = Vec::new();
 
@@ -311,12 +311,12 @@ impl Parser {
         }
 
         self.expect(TokenType::RBrace)?;
-        Ok(Statement::Compound { statements })
+        Ok(statements)
     }
 
     fn parse_statement(&mut self) -> Result<Statement, String> {
         match &self.current().token_type {
-            TokenType::LBrace => Ok(self.parse_compound_stmt()?),
+            TokenType::LBrace => Ok(Statement::Block(self.parse_block()?)),
             TokenType::If => self.parse_if_stmt(),
             TokenType::While => self.parse_while_stmt(),
             TokenType::Return => self.parse_return_stmt(),
@@ -408,13 +408,13 @@ impl Parser {
         self.expect(TokenType::LParen)?;
         let condition = self.parse_expression()?;
         self.expect(TokenType::RParen)?;
-        let then_stmt = Box::new(self.parse_statement()?);
+        let then_stmt = self.parse_block()?;
 
         let else_stmt = if matches!(self.current().token_type, TokenType::Else) {
             self.advance();
-            Some(Box::new(self.parse_statement()?))
+            self.parse_block()?
         } else {
-            None
+            Vec::new()
         };
 
         Ok(Statement::If {
@@ -429,7 +429,7 @@ impl Parser {
         self.expect(TokenType::LParen)?;
         let condition = self.parse_expression()?;
         self.expect(TokenType::RParen)?;
-        let body = Box::new(self.parse_statement()?);
+        let body = self.parse_block()?;
 
         Ok(Statement::While { condition, body })
     }

c_compiler/src/registers.rs

@@ -0,0 +1,324 @@
+use std::collections::HashMap;
+
+/// Register allocator for DSA assembly generation
+/// Manages general-purpose registers (rg0-rgf) and handles stack spilling
+pub struct RegisterAllocator {
+    /// Available general-purpose registers
+    available_registers: Vec<String>,
+
+    /// Maps variable names to their current location (register or stack offset)
+    variable_locations: HashMap<String, Location>,
+
+    /// Maps registers to the variables they currently hold
+    register_contents: HashMap<String, String>,
+
+    /// Current stack offset for local variables (relative to bpr)
+    /// Starts at -4 (going downward from base pointer)
+    stack_offset: i32,
+
+    /// Track which registers are currently in use
+    in_use: HashMap<String, bool>,
+}
+
+#[derive(Debug, Clone)]
+pub enum Location {
+    Register(String),
+    Stack(i32), // offset from bpr
+}
+
+impl RegisterAllocator {
+    pub fn new() -> Self {
+        // Initialize with available GP registers (rg0-rgf = 16 registers)
+        let registers = vec![
+            "rg0", "rg1", "rg2", "rg3", "rg4", "rg5", "rg6", "rg7", "rg8", "rg9", "rga",
+            "rgb", "rgc", "rgd", "rge", "rgf",
+        ]
+        .into_iter()
+        .map(String::from)
+        .collect();
+
+        RegisterAllocator {
+            available_registers: registers,
+            variable_locations: HashMap::new(),
+            register_contents: HashMap::new(),
+            stack_offset: -4, // Start at -4 (first local below saved bpr)
+            in_use: HashMap::new(),
+        }
+    }
+
+    /// Allocate a temporary register for expression evaluation
+    /// Returns the register name and optionally assembly code to save it
+    pub fn alloc_temp(&mut self) -> Result<(String, Vec<String>), String> {
+        let mut code = Vec::new();
+
+        // Try to find an unused register
+        for reg in &self.available_registers {
+            if !self.in_use.get(reg).unwrap_or(&false) {
+                self.in_use.insert(reg.clone(), true);
+                return Ok((reg.clone(), code));
+            }
+        }
+
+        // All registers in use - need to spill one
+        // Choose the first register with a variable we can spill
+        // Find a register to spill
+        let reg_to_spill = self
+            .available_registers
+            .iter()
+            .find(|reg| self.register_contents.contains_key(*reg))
+            .cloned();
+
+        if let Some(reg) = reg_to_spill {
+            // Spill this variable to stack
+            let spill_code = self.spill_register(&reg)?;
+            code.extend(spill_code);
+
+            self.in_use.insert(reg.clone(), true);
+            return Ok((reg, code));
+        }
+
+        Err("No registers available and nothing to spill".to_string())
+    }
+
+    /// Free a temporary register after use
+    pub fn free_temp(&mut self, reg: &str) {
+        self.in_use.insert(reg.to_string(), false);
+    }
+
+    /// Allocate a register for a named variable
+    /// Returns the register and any necessary assembly code
+    pub fn alloc_var(&mut self, var_name: &str) -> Result<(String, Vec<String>), String> {
+        // Check if variable already has a location
+        if let Some(location) = self.variable_locations.get(var_name).cloned() {
+            match location {
+                Location::Register(reg) => {
+                    return Ok((reg.clone(), Vec::new()));
+                }
+                Location::Stack(offset) => {
+                    // Variable is on stack, load it into a register
+                    let (reg, mut code) = self.alloc_temp()?;
+                    code.push(format!("\tldw bpr, {}, {}", reg, offset));
+
+                    // Update location to register
+                    self.variable_locations
+                        .insert(var_name.to_string(), Location::Register(reg.clone()));
+                    self.register_contents
+                        .insert(reg.clone(), var_name.to_string());
+
+                    return Ok((reg, code));
+                }
+            }
+        }
+
+        // Variable doesn't have a location yet, allocate a new register
+        let (reg, code) = self.alloc_temp()?;
+        self.variable_locations
+            .insert(var_name.to_string(), Location::Register(reg.clone()));
+        self.register_contents
+            .insert(reg.clone(), var_name.to_string());
+
+        Ok((reg, code))
+    }
+
+    /// Get the current location of a variable
+    pub fn get_var_location(&self, var_name: &str) -> Option<&Location> {
+        self.variable_locations.get(var_name)
+    }
+
+    /// Load a variable into a register (allocating if necessary)
+    /// Returns the register and assembly code to load it
+    pub fn load_var(&mut self, var_name: &str) -> Result<(String, Vec<String>), String> {
+        self.alloc_var(var_name)
+    }
+
+    /// Store a value from a register into a variable
+    /// Updates tracking and returns any necessary assembly code
+    pub fn store_var(&mut self, var_name: &str, source_reg: &str) -> Vec<String> {
+        let mut code = Vec::new();
+
+        // Check if variable already has a location
+        if let Some(location) = self.variable_locations.get(var_name) {
+            match location {
+                Location::Register(dest_reg) => {
+                    if dest_reg != source_reg {
+                        code.push(format!("\tmov {}, {}", source_reg, dest_reg));
+                    }
+                }
+                Location::Stack(offset) => {
+                    code.push(format!("\tstw {}, bpr, {}", source_reg, offset));
+                }
+            }
+        } else {
+            // Variable doesn't exist yet - try to allocate a register
+            if let Some(free_reg) = self.find_free_register() {
+                if &free_reg != source_reg {
+                    code.push(format!("\tmov {}, {}", source_reg, free_reg));
+                }
+                self.variable_locations
+                    .insert(var_name.to_string(), Location::Register(free_reg.clone()));
+                self.register_contents
+                    .insert(free_reg.clone(), var_name.to_string());
+                self.in_use.insert(free_reg, true);
+            } else {
+                // No free registers - allocate on stack
+                code.push(format!("\tstw {}, bpr, {}", source_reg, self.stack_offset));
+                self.variable_locations
+                    .insert(var_name.to_string(), Location::Stack(self.stack_offset));
+                self.stack_offset -= 4; // Move to next stack slot
+            }
+        }
+
+        code
+    }
+
+    /// Spill a register to the stack
+    /// Returns assembly code to perform the spill
+    fn spill_register(&mut self, reg: &str) -> Result<Vec<String>, String> {
+        let mut code = Vec::new();
+
+        if let Some(var_name) = self.register_contents.get(reg).cloned() {
+            // Store register content to stack
+            code.push(format!("\tstw {}, bpr, {}", reg, self.stack_offset));
+
+            // Update variable location
+            self.variable_locations
+                .insert(var_name.clone(), Location::Stack(self.stack_offset));
+
+            // Remove from register tracking
+            self.register_contents.remove(reg);
+
+            // Move to next stack slot
+            self.stack_offset -= 4;
+        }
+
+        Ok(code)
+    }
+
+    /// Find a free register (not currently in use)
+    fn find_free_register(&self) -> Option<String> {
+        for reg in &self.available_registers {
+            if !self.in_use.get(reg).unwrap_or(&false) {
+                return Some(reg.clone());
+            }
+        }
+        None
+    }
+
+    /// Spill all registers to stack (useful before function calls)
+    pub fn spill_all(&mut self) -> Vec<String> {
+        let mut code = Vec::new();
+
+        let regs_to_spill: Vec<String> = self.register_contents.keys().cloned().collect();
+
+        for reg in regs_to_spill {
+            if let Ok(spill_code) = self.spill_register(&reg) {
+                code.extend(spill_code);
+            }
+        }
+
+        code
+    }
+
+    /// Get the total stack space needed for local variables
+    pub fn get_stack_size(&self) -> i32 {
+        -self.stack_offset // Convert negative offset to positive size
+    }
+
+    /// Reset allocator for a new function
+    pub fn reset(&mut self) {
+        self.variable_locations.clear();
+        self.register_contents.clear();
+        self.stack_offset = -4;
+        self.in_use.clear();
+    }
+
+    /// Mark a variable as dead (no longer needed)
+    /// Frees its register if it's in one
+    pub fn free_var(&mut self, var_name: &str) {
+        if let Some(Location::Register(reg)) = self.variable_locations.get(var_name) {
+            let reg = reg.clone();
+            self.register_contents.remove(&reg);
+            self.in_use.insert(reg, false);
+        }
+        self.variable_locations.remove(var_name);
+    }
+
+    /// Save caller-saved registers before a function call
+    /// Returns assembly code to save them
+    pub fn save_caller_saved(&mut self) -> Vec<String> {
+        let mut code = Vec::new();
+
+        // For simplicity, save all currently used registers
+        // In a more sophisticated compiler, you'd only save registers that are live
+        for (reg, var_name) in self.register_contents.clone() {
+            if *self.in_use.get(&reg).unwrap_or(&false) {
+                code.push(format!("\tpush {}", reg));
+            }
+        }
+
+        code
+    }
+
+    /// Restore caller-saved registers after a function call
+    /// Returns assembly code to restore them
+    pub fn restore_caller_saved(&mut self, saved_regs: &[String]) -> Vec<String> {
+        let mut code = Vec::new();
+
+        // Restore in reverse order (LIFO)
+        for reg in saved_regs.iter().rev() {
+            code.push(format!("\tpop {}", reg));
+        }
+
+        code
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_basic_allocation() {
+        let mut allocator = RegisterAllocator::new();
+
+        let (reg1, code1) = allocator.alloc_temp().unwrap();
+        assert_eq!(code1.len(), 0); // No spill needed
+        assert_eq!(reg1, "rg0");
+
+        let (reg2, code2) = allocator.alloc_temp().unwrap();
+        assert_eq!(code2.len(), 0);
+        assert_eq!(reg2, "rg1");
+
+        allocator.free_temp(&reg1);
+
+        let (reg3, code3) = allocator.alloc_temp().unwrap();
+        assert_eq!(code3.len(), 0);
+        assert_eq!(reg3, "rg0"); // Reuses freed register
+    }
+
+    #[test]
+    fn test_variable_allocation() {
+        let mut allocator = RegisterAllocator::new();
+
+        let (reg, _) = allocator.alloc_var("x").unwrap();
+        assert_eq!(reg, "rg0");
+
+        // Requesting same variable again should return same register
+        let (reg2, _) = allocator.alloc_var("x").unwrap();
+        assert_eq!(reg2, "rg0");
+    }
+
+    #[test]
+    fn test_stack_allocation() {
+        let mut allocator = RegisterAllocator::new();
+
+        // Allocate all 16 registers
+        for i in 0..16 {
+            allocator.alloc_var(&format!("var{}", i)).unwrap();
+        }
+
+        // Next allocation should spill to stack
+        let (reg, code) = allocator.alloc_var("var16").unwrap();
+        assert!(code.len() > 0); // Should have spill code
+    }
+}