diff --git a/bootstrap/main.cpp b/bootstrap/main.cpp
index b92362a..bddb533 100644
--- a/bootstrap/main.cpp
+++ b/bootstrap/main.cpp
@@ -1146,68 +1146,6 @@ enum class Side : u8
     right,
 };
 
-struct NodeDataType
-{
-    enum class Id : u8
-    {
-        VOID,
-        INTEGER,
-        TUPLE,
-        CONTROL,
-        MEMORY,
-        POINTER,
-    };
-    Id id;
-    u8 bit_count:5;
-};
-
-union AbiInfoPayload
-{
-    NodeDataType direct;
-    NodeDataType direct_pair[2];
-    NodeDataType direct_coerce;
-    struct
-    {
-        NodeDataType type;
-        u32 alignment;
-    } indirect;
-};
-typedef union AbiInfoPayload AbiInfoPayload;
-
-struct AbiInfoAttributes
-{
-    u8 by_reg: 1;
-    u8 zero_extend: 1;
-    u8 sign_extend: 1;
-    u8 realign: 1;
-    u8 by_value: 1;
-};
-typedef struct AbiInfoAttributes AbiInfoAttributes;
-
-struct AbiInfo
-{
-    AbiInfoPayload payload;
-    u16 indices[2];
-    AbiInfoAttributes attributes;
-    AbiInfoKind kind;
-};
-
-struct FunctionPrototype
-{
-    AbiInfo* argument_type_abis; // The count for this array is "original_argument_count", not "abi_argument_count"
-    SemaType** original_argument_types;
-    // TODO: are these needed?
-    // Node::DataType* abi_argument_types;
-    // u32 abi_argument_count;
-    SemaType* original_return_type;
-    AbiInfo return_type_abi;
-    u32 original_argument_count;
-    // TODO: is this needed?
-    // Node::DataType abi_return_type;
-    u8 varags:1;
-};
-
-struct Function;
 
 global auto constexpr void_type_index = 0;
 global auto constexpr noreturn_type_index = 1;
@@ -1218,6 +1156,7 @@ global auto constexpr integer_type_offset = 5;
 global auto constexpr integer_type_count = 64 * 2;
 global auto constexpr builtin_type_count = integer_type_count + integer_type_offset + 1;
 
+struct Function;
 struct Thread
 {
     Arena* arena;
@@ -1242,30 +1181,123 @@ struct Unit
     }
 };
 
-
 struct Node;
+struct FunctionPrototype;
+
+struct NodeType
+{
+    enum class Id: u8
+    {
+        INVALID,
+        BOTTOM,
+        TOP,
+        VOID,
+        INTEGER,
+        TUPLE,
+        CONTROL,
+        MEMORY,
+        POINTER,
+    };
+    Id id;
+    union
+    {
+        struct
+        {
+            u64 constant;
+            u8 bit_count;
+            u8 is_constant;
+        } integer;
+    };
+    u8 equal(NodeType other)
+    {
+        if (id != other.id)
+        {
+            return 0;
+        }
+
+        switch (id)
+        {
+            default: trap();
+        }
+    }
+
+    u8 is_constant()
+    {
+        switch (id)
+        {
+            case Id::VOID:
+            case Id::INTEGER:
+                return 1;
+            default:
+                trap();
+        }
+    }
+};
+
+union AbiInfoPayload
+{
+    NodeType direct;
+    NodeType direct_pair[2];
+    NodeType direct_coerce;
+    struct
+    {
+        NodeType type;
+        u32 alignment;
+    } indirect;
+};
+typedef union AbiInfoPayload AbiInfoPayload;
+
+struct AbiInfoAttributes
+{
+    u8 by_reg: 1;
+    u8 zero_extend: 1;
+    u8 sign_extend: 1;
+    u8 realign: 1;
+    u8 by_value: 1;
+};
+typedef struct AbiInfoAttributes AbiInfoAttributes;
+
+struct AbiInfo
+{
+    AbiInfoPayload payload;
+    u16 indices[2];
+    AbiInfoAttributes attributes;
+    AbiInfoKind kind;
+};
 
 struct Function
 {
+    struct Prototype
+    {
+        AbiInfo* argument_type_abis; // The count for this array is "original_argument_count", not "abi_argument_count"
+        SemaType** original_argument_types;
+        // TODO: are these needed?
+        // Node::DataType* abi_argument_types;
+        // u32 abi_argument_count;
+        SemaType* original_return_type;
+        AbiInfo return_type_abi;
+        u32 original_argument_count;
+        // TODO: is this needed?
+        // Node::DataType abi_return_type;
+        u8 varags:1;
+    };
     Symbol symbol;
     Node* root_node;
     Node** parameters;
-    FunctionPrototype prototype;
+    Function::Prototype prototype;
     u32 node_count;
     u16 parameter_count;
 };
 
-struct ProjectionData
+struct ConstantIntData
 {
-    NodeDataType type;
-    u16 index;
+    u64 value;
+    Node* input;
+    u32 gvn;
+    u8 bit_count;
 };
 
-struct Output
-{
-    Node* node;
-    u16 slot;
-};
+[[nodiscard]] fn Node* add_constant_integer(Arena* arena, ConstantIntData data);
 
 // This is a node in the "sea of nodes" sense:
 // https://en.wikipedia.org/wiki/Sea_of_nodes
@@ -1277,18 +1309,27 @@ struct Node
         PROJECTION,
         RETURN,
         CONSTANT_INT,
+        INT_ADD,
+        INT_SUB,
     };
 
-    static_assert(sizeof(NodeDataType) <= 2);
+    using Type = NodeType;
+
+
+    struct Output
+    {
+        Node* node;
+        u16 slot;
+    };
 
     Node** inputs;
     Output* outputs;
     u32 gvn;
+    Type type;
     u16 input_count;
     u16 input_capacity;
     u16 output_count;
     u16 output_capacity;
-    NodeDataType data_type;
     Id id;
 
     union
@@ -1297,7 +1338,6 @@ struct Node
         {
             u32 index;
         } projection;
-        u64 constant_int;
     };
 
     forceinline Slice<Node*> get_inputs()
@@ -1318,7 +1358,7 @@ struct Node
 
     struct NodeData
     {
-        NodeDataType type;
+        Type type;
         u16 input_count;
         Id id;
     };
@@ -1339,11 +1379,11 @@ struct Node
             .inputs = arena->allocate_many<Node*>(data.input_capacity),
             .outputs = arena->allocate_many<Output>(output_capacity),
             .gvn = data.gvn,
+            .type = data.s.type,
             .input_count = data.s.input_count,
             .input_capacity = data.input_capacity,
             .output_count = output_count,
             .output_capacity = output_capacity,
-            .data_type = data.s.type,
             .id = data.s.id,
         };
 
@@ -1370,41 +1410,53 @@ struct Node
     {
         return add_from_function_dynamic(arena, function, data, data.input_count);
     }
+
+    struct ProjectionData
+    {
+        Node::Type type;
+        u16 index;
+    };
     
     [[nodiscard]] Node* project(Arena* arena, Function* function, ProjectionData data)
     {
-        assert(data_type.id == NodeDataType::Id::TUPLE);
+        assert(type.id == Type::Id::TUPLE);
 
         Node* projection = Node::add_from_function(arena, function, {
             .input_count = 1,
         });
         assert(projection != this);
         projection->id = Node::Id::PROJECTION;
-        projection->data_type = data.type;
+        projection->type = data.type;
         // projection->reallocate_edges(unit, 4);
         projection->input_count = 1;
-        projection->set_input(this, 0);
+        projection->set_input(arena, this, 0);
         projection->projection.index = data.index;
 
         return projection;
     }
 
-    void set_input(Node* input, u16 slot)
+    void set_input(Arena* arena, Node* input, u16 slot)
     {
         assert(slot < input_count);
         remove_output(slot);
         inputs[slot] = input;
         if (input)
         {
-            add_output(input, slot);
+            add_output(arena, input, slot);
         }
     }
 
-    void add_output(Node* input, u16 slot)
+    void add_output(Arena* arena, Node* input, u16 slot)
     {
         if (input->output_count >= input->output_capacity)
         {
-            trap();
+            auto new_capacity = max<u32>(input->output_count, (u32)input->output_capacity * 2);
+            assert(new_capacity <= 0xffff);
+            auto* new_array = arena->allocate_many<Output>(new_capacity);
+            memcpy(new_array, input->outputs, sizeof(Output) * input->output_count);
+            memset(new_array + input->output_count, 0, sizeof(Output) * (new_capacity - input->output_count));
+            input->outputs = new_array;
+            input->output_capacity = new_capacity;
         }
 
         auto index = input->output_count;
@@ -1439,6 +1491,9 @@ struct Node
         case Id::PROJECTION:
         case Id::CONSTANT_INT:
             break;
+        case Id::INT_ADD:
+        case Id::INT_SUB:
+            trap();
         }
 
         return is_good_id | is_projection() | cfg_is_control_projection();
@@ -1457,16 +1512,16 @@ struct Node
 
     u8 cfg_is_control_projection()
     {
-        return is_projection() & (data_type.id == NodeDataType::Id::CONTROL);
+        return is_projection() & (type.id == Node::Type::Id::CONTROL);
     }
 
     u8 is_cfg_control()
     {
-        switch (data_type.id)
+        switch (type.id)
         {
-        case NodeDataType::Id::CONTROL:
+            case Node::Type::Id::CONTROL:
             return 1;
-        case NodeDataType::Id::TUPLE:
+        case Node::Type::Id::TUPLE:
             for (Output& output : get_outputs())
             {
                 if (output.node->cfg_is_control_projection())
@@ -1478,8 +1533,164 @@ struct Node
             return 0;
         }
     }
+
+    Node* idealize()
+    {
+        switch (id)
+        {
+        case Id::ROOT:
+        case Id::PROJECTION:
+        case Id::RETURN:
+        case Id::CONSTANT_INT:
+        case Id::INT_ADD:
+        case Id::INT_SUB:
+            return 0;
+        }
+    }
+
+    u8 is_unused()
+    {
+        return output_count == 0;
+    }
+
+    u8 is_dead()
+    {
+        return is_unused() & (input_count == 0) & (type.id == Node::Type::Id::INVALID);
+    }
+
+    void kill(Arena* arena)
+    {
+        assert(is_unused());
+
+        for (u16 i = 0; i < input_count; i += 1)
+        {
+            set_input(arena, 0, i);
+        }
+        input_count = 0;
+        type = {};
+
+        assert(is_dead());
+    }
+
+    static auto constexpr enable_peephole = 1;
+    Node* peephole(Arena* arena, Function* function)
+    {
+        Node::Type type = this->type = compute();
+
+        if (!enable_peephole)
+        {
+            return this;
+        }
+
+        if ((!is_constant()) & type.is_constant())
+        {
+            this->kill(arena);
+            auto gvn = function->node_count;
+            function->node_count += 1;
+            auto* constant_int = Node::add(arena, {
+                .s =
+                {
+                    .type = type,
+                    .input_count = 1,
+                    .id = Node::Id::CONSTANT_INT,
+                },
+                .gvn = gvn,
+                .input_capacity = 1,
+            });
+            constant_int->set_input(arena, function->root_node, 0);
+            auto* result = constant_int->peephole(arena, function);
+            return result;
+        }
+
+        Node* n = idealize();
+        return n ? n : this;
+    }
+
+    u8 is_constant()
+    {
+        switch (id)
+        {
+            default:
+                return 0;
+            case Id::CONSTANT_INT:
+                return 1;
+        }
+    }
+
+    Node::Type compute()
+    {
+        switch (id)
+        {
+            case Node::Id::INT_ADD:
+            case Node::Id::INT_SUB:
+                {
+                    auto left_type = inputs[1]->type;
+                    auto right_type = inputs[2]->type;
+                    if ((left_type.id == Node::Type::Id::INTEGER) & (right_type.id == Node::Type::Id::INTEGER))
+                    {
+                        if (left_type.is_constant() & right_type.is_constant())
+                        {
+                            u64 result;
+                            switch (id)
+                            {
+                            case Id::ROOT:
+                            case Id::PROJECTION:
+                            case Id::RETURN:
+                            case Id::CONSTANT_INT:
+                                trap();
+                            case Id::INT_ADD:
+                                result = left_type.integer.constant + right_type.integer.constant;
+                                break;
+                            case Id::INT_SUB:
+                                result = left_type.integer.constant - right_type.integer.constant;
+                                break;
+                            }
+
+
+                            return Node::Type{
+                                .id = Node::Type::Id::INTEGER,
+                                .integer = {
+                                    .constant = result,
+                                    .bit_count = left_type.integer.bit_count,
+                                    .is_constant = 1,
+                                },
+                            };
+                        }
+                    }
+                    trap();
+                }
+            case Node::Id::CONSTANT_INT:
+                return type;
+            default:
+                trap();
+        }
+    }
 };
 
+[[nodiscard]] fn Node* add_constant_integer(Arena* arena, ConstantIntData data)
+{
+    auto* constant_int = Node::add(arena, {
+        .s = {
+            .type =
+            {
+                .id = Node::Type::Id::INTEGER,
+                .integer =
+                {
+                    .constant = data.value,
+                    .bit_count = data.bit_count,
+                    .is_constant = 1,
+                },
+            },
+            .input_count = 1,
+            .id = Node::Id::CONSTANT_INT,
+        },
+        .gvn = data.gvn,
+        .input_capacity = 1,
+    });
+    constant_int->set_input(arena, data.input, 0);
+    return constant_int;
+}
+
 struct WorkList
 {
     using BitsetBackingType = u32;
@@ -2254,34 +2465,25 @@ fn u64 parse_hex(String string)
     return value;
 }
 
-struct ConstantIntData
+fn u64 parse_decimal(String string)
 {
-    u64 value;
-    Node* input;
-    u32 gvn;
-    u8 bit_count;
-};
+    u64 value = 0;
+    for (u8 ch : string)
+    {
+        assert(((ch >= '0') & (ch <= '9')));
+        value = (value * 10) + (ch - '0');
+    }
 
-[[nodiscard]] fn Node* add_constant_integer(Arena* arena, ConstantIntData data)
-{
-    auto* constant_int = Node::add(arena, {
-        .s = {
-            .type = { .id = NodeDataType::Id::INTEGER, .bit_count = data.bit_count, },
-            .input_count = 1,
-            .id = Node::Id::CONSTANT_INT,
-        },
-        .gvn = data.gvn,
-        .input_capacity = 1,
-    });
-    constant_int->constant_int = data.value;
-    constant_int->set_input(data.input, 0);
-    return constant_int;
+    return value;
 }
 
+
+
 [[nodiscard]] fn Node* parse_constant_integer(Parser* parser, Arena* arena, String src, SemaType* type, u32 gvn, Node* input)
 {
     u64 value = 0;
-    auto starting_ch = src[parser->i];
+    auto starting_index = parser->i;
+    auto starting_ch = src[starting_index];
 
     if (starting_ch == '0')
     {
@@ -2336,7 +2538,13 @@ struct ConstantIntData
     }
     else
     {
-        trap();
+        while (is_decimal_digit(src[parser->i]))
+        {
+            parser->i += 1;
+        }
+
+        auto slice = src.slice(starting_index, parser->i);
+        value = parse_decimal(slice);
     }
 
     Node* result = add_constant_integer(arena, {
@@ -2345,6 +2553,7 @@ struct ConstantIntData
         .gvn = gvn,
         .bit_count = type->get_bit_count(),
     });
+
     return result;
 }
 
@@ -2439,6 +2648,10 @@ struct ConstantIntData
     enum class CurrentOperation
     {
         NONE,
+        ADD,
+        ADD_ASSIGN,
+        SUB,
+        SUB_ASSIGN,
     };
 
     u64 iterations = 0;
@@ -2472,8 +2685,42 @@ struct ConstantIntData
         case CurrentOperation::NONE:
             previous_node = current_node;
             break;
+        case CurrentOperation::ADD:
+        case CurrentOperation::SUB:
+            {
+                Node::Id id;
+                switch (current_operation)
+                {
+                case CurrentOperation::NONE:
+                    trap();
+                case CurrentOperation::ADD:
+                    id = Node::Id::INT_ADD;
+                    break;
+                case CurrentOperation::SUB:
+                    id = Node::Id::INT_SUB;
+                    break;
+                case CurrentOperation::ADD_ASSIGN:
+                case CurrentOperation::SUB_ASSIGN:
+                    trap();
+                }
+
+                auto* binary = Node::add_from_function(arena, analyzer->function, {
+                    .type = current_node->type,
+                    .input_count = 3,
+                    .id = id,
+                });
+                binary->set_input(arena, 0, 0);
+                binary->set_input(arena, previous_node, 1);
+                binary->set_input(arena, current_node, 2);
+
+                previous_node = binary;
+            } break;
+        default:
+            trap();
         }
 
+        previous_node = previous_node->peephole(arena, analyzer->function);
+
         auto original_index = parser->i;
         u8 original = src[original_index];
 
@@ -2484,10 +2731,40 @@ struct ConstantIntData
             case parenthesis_close:
             case bracket_close:
                 return previous_node;
+            case '+':
+                current_operation = CurrentOperation::ADD;
+                parser->i += 1;
+
+                switch (src[parser->i])
+                {
+                    case '=':
+                        current_operation = CurrentOperation::ADD_ASSIGN;
+                        parser->i += 1;
+                        break;
+                    default:
+                        break;
+                }
+                break;
+            case '-':
+                current_operation = CurrentOperation::SUB;
+                parser->i += 1;
+
+                switch (src[parser->i])
+                {
+                    case '=':
+                        current_operation = CurrentOperation::SUB_ASSIGN;
+                        parser->i += 1;
+                        break;
+                    default:
+                        break;
+                }
+                break;
             default:
                 trap();
         }
 
+        skip_space(parser, src);
+
         iterations += 1;
     }
 }
@@ -2520,12 +2797,12 @@ fn void analyze_local_block(Analyzer* analyzer, Parser* parser, Unit* unit, Aren
                 Function* function = analyzer->function;
 
                 Node* ret_node = Node::add_from_function(arena, function, {
-                    .type = { .id = NodeDataType::Id::CONTROL },
+                    .type = { .id = Node::Type::Id::CONTROL },
                     .input_count = 2,
                     .id = Node::Id::RETURN,
                 });
-                ret_node->set_input(function->root_node, 0);
-                ret_node->set_input(return_value, 1);
+                ret_node->set_input(arena, function->root_node, 0);
+                ret_node->set_input(arena, return_value, 1);
             }
             else
             {
@@ -3022,7 +3299,7 @@ fn void analyze_function(Parser* parser, Thread* thread, Unit* unit, String src)
             };
             
             function->root_node = Node::add_from_function_dynamic(thread->arena, function, {
-                .type = { .id = NodeDataType::Id::TUPLE },
+                .type = { .id = Node::Type::Id::TUPLE },
                 .input_count = 2,
                 .id = Node::Id::ROOT,
             }, 4);
@@ -3030,7 +3307,7 @@ fn void analyze_function(Parser* parser, Thread* thread, Unit* unit, String src)
             // TODO: revisit
 
             // auto* control_node = root_node->project(unit, function, {
-            //     .type = { .id = NodeDataType::Id::CONTROL },
+            //     .type = { .id = Node::Type::Id::CONTROL },
             // });
             // auto* memory_node = root_node->project(unit, function, {});
             // auto* pointer_node = root_node->project(unit, function, {});
@@ -3048,7 +3325,7 @@ fn void analyze_function(Parser* parser, Thread* thread, Unit* unit, String src)
             // TODO: revisit
             // Node* ret_node = Node::add_from_function(unit, function);
             // ret_node->id = Node::Id::RETURN;
-            // ret_node->data_type = { .id = NodeDataType::Id::CONTROL };
+            // ret_node->data_type = { .id = Node::Type::Id::CONTROL };
             // ret_node->reallocate_edges(unit, 4);
             // ret_node->input_count = 2;
             // ret_node->set_input(unit, function, root_node, 0);
@@ -3186,7 +3463,7 @@ global Instance instance;
 //                 continue;
 //             }
 //
-//             if (node->data_type.id == NodeDataType::Id::MEMORY)
+//             if (node->data_type.id == Node::Type::Id::MEMORY)
 //             {
 //                 trap();
 //             }
@@ -3219,6 +3496,7 @@ global Instance instance;
 
 String test_file_paths[] = {
     strlit("tests/first/main.nat"),
+    strlit("tests/constant_prop/main.nat"),
 };
 
 extern "C" void entry_point()
diff --git a/tests/constant_prop/main.nat b/tests/constant_prop/main.nat
new file mode 100644
index 0000000..f376aff
--- /dev/null
+++ b/tests/constant_prop/main.nat
@@ -0,0 +1,4 @@
+fn[cc(.c)] main [export] () s32
+{
+    return 2 + 4 - 1 - 5;
+}