diff --git a/hbbytecode/src/lib.rs b/hbbytecode/src/lib.rs
index 6a91fbc..a6ccc5a 100644
--- a/hbbytecode/src/lib.rs
+++ b/hbbytecode/src/lib.rs
@@ -17,7 +17,7 @@ type OpD = u64;
 /// Has to be valid to be decoded from bytecode.
 pub unsafe trait BytecodeItem {}
 macro_rules! define_items {
-    ($($name:ident ($($item:ident),* $(,)?)),* $(,)?) => {
+    ($($name:ident ($($nm:ident: $item:ident),* $(,)?)),* $(,)?) => {
         $(
             #[derive(Clone, Copy, Debug)]
             #[repr(packed)]
@@ -25,13 +25,13 @@ macro_rules! define_items {
             unsafe impl BytecodeItem for $name {}
 
             impl Encodable for $name {
-                fn encode(self, buffer: &mut impl Buffer) {
-                    let array = unsafe {
-                        core::mem::transmute::<Self, [u8; core::mem::size_of::<Self>()]>(self)
-                    };
-                    for byte in array {
-                        unsafe { buffer.write(byte) };
-                    }
+                fn encode(self, _buffer: &mut impl Buffer) {
+                    let Self($($nm),*) = self;
+                    $(
+                        for byte in $nm.to_le_bytes() {
+                            unsafe { _buffer.write(byte) };
+                        }
+                    )*
                 }
 
                 fn encode_len(self) -> usize {
@@ -43,26 +43,26 @@ macro_rules! define_items {
 }
 
 define_items! {
-    OpsRR   (OpR, OpR          ),
-    OpsRRR  (OpR, OpR, OpR     ),
-    OpsRRRR (OpR, OpR, OpR, OpR),
-    OpsRRB  (OpR, OpR, OpB     ),
-    OpsRRH  (OpR, OpR, OpH     ),
-    OpsRRW  (OpR, OpR, OpW     ),
-    OpsRRD  (OpR, OpR, OpD     ),
-    OpsRB   (OpR, OpB          ),
-    OpsRH   (OpR, OpH          ),
-    OpsRW   (OpR, OpW          ),
-    OpsRD   (OpR, OpD          ),
-    OpsRRA  (OpR, OpR, OpA     ),
-    OpsRRAH (OpR, OpR, OpA, OpH),
-    OpsRROH (OpR, OpR, OpO, OpH),
-    OpsRRPH (OpR, OpR, OpP, OpH),
-    OpsRRO  (OpR, OpR, OpO     ),
-    OpsRRP  (OpR, OpR, OpP     ),
-    OpsO    (OpO,              ),
-    OpsP    (OpP,              ),
-    OpsN    (                  ),
+    OpsRR   (a: OpR, b: OpR                ),
+    OpsRRR  (a: OpR, b: OpR, c: OpR        ),
+    OpsRRRR (a: OpR, b: OpR, c: OpR, d: OpR),
+    OpsRRB  (a: OpR, b: OpR, c: OpB        ),
+    OpsRRH  (a: OpR, b: OpR, c: OpH        ),
+    OpsRRW  (a: OpR, b: OpR, c: OpW        ),
+    OpsRRD  (a: OpR, b: OpR, c: OpD        ),
+    OpsRB   (a: OpR, b: OpB                ),
+    OpsRH   (a: OpR, b: OpH                ),
+    OpsRW   (a: OpR, b: OpW                ),
+    OpsRD   (a: OpR, b: OpD                ),
+    OpsRRA  (a: OpR, b: OpR, c: OpA        ),
+    OpsRRAH (a: OpR, b: OpR, c: OpA, d: OpH),
+    OpsRROH (a: OpR, b: OpR, c: OpO, d: OpH),
+    OpsRRPH (a: OpR, b: OpR, c: OpP, d: OpH),
+    OpsRRO  (a: OpR, b: OpR, c: OpO        ),
+    OpsRRP  (a: OpR, b: OpR, c: OpP        ),
+    OpsO    (a: OpO,                       ),
+    OpsP    (a: OpP,                       ),
+    OpsN    (                              ),
 }
 
 unsafe impl BytecodeItem for u8 {}
diff --git a/hblang/src/codegen.rs b/hblang/src/codegen.rs
index 42e5b79..df70544 100644
--- a/hblang/src/codegen.rs
+++ b/hblang/src/codegen.rs
@@ -1,40 +1,403 @@
-use crate::parser::Type;
+use std::{iter::Cycle, ops::Range};
+
+use crate::{
+    lexer::Ty,
+    parser::{Exp, Function, Item, Literal, Struct, Type},
+    typechk::Type,
+};
+
+//| Register   | Description         | Saver  |
+//|:-----------|:--------------------|:-------|
+//| r0         | Hard-wired zero     | N/A    |
+//| r1 - r2    | Return values       | Caller |
+//| r2 - r11   | Function parameters | Caller |
+//| r12 - r30  | General purpose     | Caller |
+//| r31        | Return address      | Caller |
+//| r32 - r253 | General purpose     | Callee |
+//| r254       | Stack pointer       | Callee |
+//| r255       | Thread pointer      | N/A    |
 
 struct RegAlloc {
-    pub regs: Box<[Option<usize>; 256]>,
+    pub regs:        Box<[Option<usize>; 256]>,
+    pub used:        Box<[bool; 256]>,
+    pub spill_cycle: Cycle<Range<usize>>,
+}
+
+impl RegAlloc {
+    fn alloc_regurn(&mut self, slot: SlotId) -> Option<Reg> {
+        self.regs[1..2]
+            .iter_mut()
+            .position(|reg| {
+                if reg.is_none() {
+                    *reg = Some(slot);
+                    true
+                } else {
+                    false
+                }
+            })
+            .map(|reg| reg as Reg + 1)
+    }
+
+    fn alloc_general(&mut self, slot: SlotId) -> Option<Reg> {
+        self.regs[32..254]
+            .iter_mut()
+            .zip(&mut self.used[32..254])
+            .position(|(reg, used)| {
+                if reg.is_none() {
+                    *reg = Some(slot);
+                    *used = true;
+                    true
+                } else {
+                    false
+                }
+            })
+            .map(|reg| reg as Reg + 32)
+    }
+
+    fn free(&mut self, reg: Reg) {
+        assert!(self.regs[reg as usize].take().is_some());
+    }
+
+    fn spill(&mut self, for_slot: SlotId) -> (Reg, SlotId) {
+        let to_spill = self.spill_cycle.next().unwrap();
+        let slot = self.regs[to_spill].replace(for_slot).unwrap();
+        (to_spill as Reg + 32, slot)
+    }
+
+    fn restore(&mut self, reg: Reg, slot: SlotId) -> SlotId {
+        self.regs[reg as usize].replace(slot).unwrap()
+    }
+}
+
+pub struct ParamAlloc {
+    reg_range: Range<Reg>,
+    stack:     Offset,
+}
+
+impl ParamAlloc {
+    fn new(reg_range: Range<Reg>) -> Self {
+        Self {
+            stack: 16,
+            reg_range,
+        }
+    }
+
+    fn alloc(&mut self, mut size: usize) -> Value {
+        match self.try_alloc_regs(size) {
+            Some(reg) => reg,
+            None => panic!("Too many arguments o7"),
+        }
+    }
+
+    fn try_alloc_regs(&mut self, size: usize) -> Option<Value> {
+        let mut needed = size.div_ceil(8);
+        if needed > 2 {
+            needed = 1; // passed by ref
+        }
+
+        if self.reg_range.len() < needed {
+            return None;
+        }
+
+        match needed {
+            1 => {
+                let reg = self.reg_range.start;
+                self.reg_range.start += 1;
+                Some(Value::Reg(reg))
+            }
+            2 => {
+                let reg = self.reg_range.start;
+                self.reg_range.start += 2;
+                Some(Value::Pair(reg, reg + 1))
+            }
+            _ => unreachable!(),
+        }
+    }
+}
+
+impl Default for RegAlloc {
+    fn default() -> Self {
+        Self {
+            regs:        Box::new([None; 256]),
+            used:        Box::new([false; 256]),
+            spill_cycle: (32..254).cycle(),
+        }
+    }
 }
 
 struct Variable {
     name:     String,
-    location: usize,
+    location: SlotId,
 }
 
-enum Symbol {
-    Type(String, Type),
-    Func(String, Vec<Type>, Type),
-}
+type SlotId = usize;
 
 struct Slot {
     ty:    Type,
     value: Value,
 }
 
+#[repr(transparent)]
+struct InstBuffer {
+    buffer: Vec<u8>,
+}
+
+impl InstBuffer {
+    fn new(vec: &mut Vec<u8>) -> &mut Self {
+        unsafe { &mut *(vec as *mut Vec<u8> as *mut Self) }
+    }
+}
+
+impl hbbytecode::Buffer for InstBuffer {
+    fn reserve(&mut self, bytes: usize) {
+        self.buffer.reserve(bytes);
+    }
+
+    unsafe fn write(&mut self, byte: u8) {
+        self.buffer.push(byte);
+    }
+}
+
+type Reg = u8;
+type Offset = i32;
+
 enum Value {
-    Reg(u8),
-    Stack(i32),
+    Pair(Reg, Reg),
+    Reg(Reg),
+    Stack(Offset),
     Imm(u64),
+    Spilled(Reg, SlotId),
+    DoubleSpilled(SlotId, Offset),
 }
 
 type Label = usize;
+type Data = usize;
 
-pub struct Generator {
-    regs:        RegAlloc,
-    symbols:     Vec<Symbol>,
-    variables:   Vec<Variable>,
-    slots:       Vec<Slot>,
-    relocations: Vec<(Label, usize)>,
+pub struct LabelReloc {
+    pub label:  Label,
+    pub offset: usize,
 }
 
-impl Generator {
-    pub fn gen();
+pub struct DataReloc {
+    pub data:   Data,
+    pub offset: usize,
+}
+
+#[must_use]
+pub struct Frame {
+    pub slot_count: usize,
+    pub var_count:  usize,
+}
+
+#[derive(Default)]
+pub struct Generator<'a> {
+    ast: &'a [Item],
+
+    func_labels: Vec<(String, Label)>,
+
+    regs:      RegAlloc,
+    variables: Vec<Variable>,
+    slots:     Vec<Slot>,
+
+    labels:       Vec<Option<usize>>,
+    label_relocs: Vec<LabelReloc>,
+
+    data:        Vec<Option<usize>>,
+    data_relocs: Vec<DataReloc>,
+
+    code_section: Vec<u8>,
+    data_section: Vec<u8>,
+}
+
+impl<'a> Generator<'a> {
+    fn generate(mut self) -> Vec<u8> {
+        for item in self.ast {
+            let Item::Function(f) = item else { continue };
+            self.generate_function(f);
+        }
+
+        self.link()
+    }
+
+    fn generate_function(&mut self, f: &Function) {
+        let frame = self.push_frame();
+
+        let mut param_alloc = ParamAlloc::new(2..12);
+
+        for param in f.args.iter() {
+            let param_size = self.size_of(&param.ty);
+            let slot = self.add_slot(param.ty.clone(), param_alloc.alloc(param_size));
+            self.add_variable(param.name.clone(), slot);
+        }
+
+        for stmt in f.body.iter() {
+            assert!(self
+                .generate_expr(Some(Type::Builtin(Ty::Void)), stmt)
+                .is_none());
+        }
+
+        self.pop_frame(frame);
+    }
+
+    fn generate_expr(&mut self, expected: Option<Type>, expr: &Exp) -> Option<SlotId> {
+        let value = match expr {
+            Exp::Literal(lit) => match lit {
+                Literal::Int(i) => self.add_slot(expected.unwrap(), Value::Imm(*i)),
+                Literal::Bool(b) => self.add_slot(Type::Builtin(Ty::Bool), Value::Imm(*b as u64)),
+            },
+            Exp::Variable(ident) => self.lookup_variable(ident).unwrap().location,
+            Exp::Call { name, args } => todo!(),
+            Exp::Ctor { name, fields } => todo!(),
+            Exp::Index { base, index } => todo!(),
+            Exp::Field { base, field } => todo!(),
+            Exp::Unary { op, exp } => todo!(),
+            Exp::Binary { op, left, right } => todo!(),
+            Exp::If { cond, then, else_ } => todo!(),
+            Exp::Let { name, ty, value } => todo!(),
+            Exp::For {
+                init,
+                cond,
+                step,
+                block,
+            } => todo!(),
+            Exp::Block(_) => todo!(),
+            Exp::Return(_) => todo!(),
+            Exp::Break => todo!(),
+            Exp::Continue => todo!(),
+        };
+
+        if let Some(expected) = expected {
+            let actual = self.slots[value].ty.clone();
+            assert_eq!(expected, actual);
+        }
+
+        Some(value)
+    }
+
+    fn size_of(&self, ty: &Type) -> usize {
+        match ty {
+            Type::Builtin(ty) => match ty {
+                Ty::U8 | Ty::I8 | Ty::Bool => 1,
+                Ty::U16 | Ty::I16 => 2,
+                Ty::U32 | Ty::I32 => 4,
+                Ty::U64 | Ty::I64 => 8,
+                Ty::Void => 0,
+            },
+            Type::Struct(name) => self
+                .lookup_struct(name)
+                .fields
+                .iter()
+                .map(|field| self.size_of(&field.ty))
+                .sum(),
+            Type::Pinter(_) => 8,
+        }
+    }
+
+    fn add_variable(&mut self, name: String, location: SlotId) {
+        self.variables.push(Variable { name, location });
+    }
+
+    fn add_slot(&mut self, ty: Type, value: Value) -> SlotId {
+        let slot = self.slots.len();
+        self.slots.push(Slot { ty, value });
+        slot
+    }
+
+    fn link(mut self) -> Vec<u8> {
+        for reloc in self.label_relocs {
+            let label = self.labels[reloc.label].unwrap();
+            let offset = reloc.offset;
+            let target = label - offset;
+            let target_bytes = u64::to_le_bytes(target as u64);
+            self.code_section[offset..offset + 8].copy_from_slice(&target_bytes);
+        }
+
+        for reloc in self.data_relocs {
+            let data = self.data[reloc.data].unwrap();
+            let offset = reloc.offset;
+            let target = data;
+            let target_bytes = u64::to_le_bytes((target + self.code_section.len()) as u64);
+            self.data_section[offset..offset + 8].copy_from_slice(&target_bytes);
+        }
+
+        self.code_section.extend_from_slice(&self.data_section);
+        self.code_section
+    }
+
+    fn lookup_func_label(&mut self, name: &str) -> Label {
+        if let Some(label) = self.func_labels.iter().find(|(n, _)| n == name) {
+            return label.1;
+        }
+
+        panic!("Function not found: {}", name);
+    }
+
+    fn declare_label(&mut self) -> Label {
+        self.labels.push(None);
+        self.labels.len() - 1
+    }
+
+    fn define_label(&mut self, label: Label) {
+        self.labels[label] = Some(self.code_section.len());
+    }
+
+    fn declare_data(&mut self) -> Data {
+        self.data.push(None);
+        self.data.len() - 1
+    }
+
+    fn define_data(&mut self, data: Data, bytes: &[u8]) {
+        self.data[data] = Some(self.data.len());
+        self.data_section.extend_from_slice(bytes);
+    }
+
+    fn lookup_struct(&self, name: &str) -> &Struct {
+        self.lookup_item(name)
+            .and_then(|item| match item {
+                Item::Struct(s) => Some(s),
+                _ => panic!("Not a struct: {}", name),
+            })
+            .expect("Struct not found")
+    }
+
+    fn lookup_function(&self, name: &str) -> &Function {
+        self.lookup_item(name)
+            .and_then(|item| match item {
+                Item::Function(f) => Some(f),
+                _ => panic!("Not a function: {}", name),
+            })
+            .expect("Function not found")
+    }
+
+    fn lookup_item(&self, name: &str) -> Option<&Item> {
+        self.ast.iter().find(|item| match item {
+            Item::Import(_) => false,
+            Item::Struct(s) => s.name == name,
+            Item::Function(f) => f.name == name,
+        })
+    }
+
+    fn lookup_variable(&self, name: &str) -> Option<&Variable> {
+        self.variables.iter().find(|variable| variable.name == name)
+    }
+
+    fn push_frame(&mut self) -> Frame {
+        Frame {
+            slot_count: self.slots.len(),
+            var_count:  self.variables.len(),
+        }
+    }
+
+    fn pop_frame(&mut self, frame: Frame) {
+        self.slots.truncate(frame.slot_count);
+        self.variables.truncate(frame.var_count);
+    }
+}
+
+pub fn generate(ast: &[Item]) -> Vec<u8> {
+    Generator {
+        ast,
+        ..Default::default()
+    }
+    .generate()
 }
diff --git a/hblang/src/lexer.rs b/hblang/src/lexer.rs
index d04b97c..11ee266 100644
--- a/hblang/src/lexer.rs
+++ b/hblang/src/lexer.rs
@@ -144,6 +144,7 @@ gen_token! {
         },
         regexes: {
             Ident = "[a-zA-Z_][a-zA-Z0-9_]*",
+            String = r#""([^"\\]|\\.)*""#,
             Number = "[0-9]+",
         },
     }
diff --git a/hblang/src/lib.rs b/hblang/src/lib.rs
index 17e1be4..0477679 100644
--- a/hblang/src/lib.rs
+++ b/hblang/src/lib.rs
@@ -1,3 +1,5 @@
+#![allow(dead_code)]
+
 mod codegen;
 mod lexer;
 mod parser;
diff --git a/hblang/src/parser.rs b/hblang/src/parser.rs
index 799ef5b..4bb0282 100644
--- a/hblang/src/parser.rs
+++ b/hblang/src/parser.rs
@@ -13,7 +13,7 @@ pub enum Item {
     Function(Function),
 }
 
-#[derive(Clone, Debug)]
+#[derive(Clone, Debug, PartialEq, Eq)]
 pub enum Type {
     Builtin(Ty),
     Struct(String),
@@ -22,6 +22,7 @@ pub enum Type {
 
 #[derive(Clone, Debug)]
 pub struct Struct {
+    pub name:   String,
     pub fields: Vec<Field>,
 }
 
@@ -104,7 +105,7 @@ pub enum Exp {
 
 #[derive(Clone, Debug)]
 pub enum Literal {
-    Int(i64),
+    Int(u64),
     Bool(bool),
 }
 
@@ -197,6 +198,7 @@ impl<'a> Parser<'a> {
         match token.kind {
             TokenKind::Struct => Some(self.parse_struct()),
             TokenKind::Fn => Some(self.parse_function()),
+            TokenKind::Use => Some(Item::Import(self.expect(TokenKind::String).value)),
             tkn => {
                 let (line, col) = self.pos_to_line_col(token.span.start);
                 panic!("Unexpected {:?} at {}:{}", tkn, line, col)
@@ -301,7 +303,6 @@ impl<'a> Parser<'a> {
                 let value = token.value.parse().unwrap();
                 Exp::Literal(Literal::Int(value))
             }
-            TokenKind::Fn => todo!(),
             TokenKind::Let => {
                 let name = self.expect(TokenKind::Ident).value;
                 let ty = self.try_advance(TokenKind::Colon).then(|| self.type_());
@@ -332,7 +333,6 @@ impl<'a> Parser<'a> {
                     else_,
                 }
             }
-            TokenKind::Else => todo!(),
             TokenKind::For => {
                 let params =
                     self.sequence(TokenKind::Semicolon, TokenKind::LBrace, Self::parse_expr);
@@ -385,21 +385,10 @@ impl<'a> Parser<'a> {
                     .then(|| Box::new(self.parse_expr()));
                 Exp::Return(value)
             }
-            TokenKind::Break => todo!(),
-            TokenKind::Continue => todo!(),
-            TokenKind::Struct => todo!(),
-            TokenKind::RBrace => todo!(),
-            TokenKind::RParen => todo!(),
-            TokenKind::LBracket => todo!(),
-            TokenKind::RBracket => todo!(),
-            TokenKind::Colon => todo!(),
-            TokenKind::Semicolon => todo!(),
-            TokenKind::Comma => todo!(),
             TokenKind::Op(op) => Exp::Unary {
                 op,
                 exp: Box::new(self.parse_expr()),
             },
-            TokenKind::Ty(_) => todo!(),
             TokenKind::Dot => {
                 let token = self.expect_any();
                 match token.kind {
@@ -417,6 +406,25 @@ impl<'a> Parser<'a> {
                     }
                 }
             }
+
+            TokenKind::Ty(_)
+            | TokenKind::String
+            | TokenKind::Use
+            | TokenKind::Break
+            | TokenKind::Continue
+            | TokenKind::Struct
+            | TokenKind::RBrace
+            | TokenKind::RParen
+            | TokenKind::LBracket
+            | TokenKind::RBracket
+            | TokenKind::Colon
+            | TokenKind::Semicolon
+            | TokenKind::Comma
+            | TokenKind::Fn
+            | TokenKind::Else => {
+                let (line, col) = self.pos_to_line_col(token.span.start);
+                panic!("Unexpected {:?} at {}:{}", token.kind, line, col)
+            }
         };
 
         loop {