Experiment with optimizations and benches

Cargo.lock

@@ -322,7 +322,6 @@ dependencies = [
  "rand",
  "serde",
  "serde_json",
- "slab",
  "smallvec",
  "smartstring",
 ]
@@ -727,15 +726,6 @@ dependencies = [
  "serde",
 ]
 
-[[package]]
-name = "slab"
-version = "0.4.9"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8f92a496fb766b417c996b9c5e57daf2f7ad3b0bebe1ccfca4856390e3d3bb67"
-dependencies = [
- "autocfg",
-]
-
 [[package]]
 name = "smallvec"
 version = "1.13.2"

dust-lang/Cargo.toml

@@ -23,7 +23,6 @@ smartstring = { version = "1.0.1", features = [
     "serde",
 ], default-features = false }
 bitflags = { version = "2.6.0", features = ["serde"] }
-slab = "0.4.9"
 
 [dev-dependencies]
 criterion = { version = "0.3.4", features = ["html_reports"] }
@@ -32,6 +31,10 @@ criterion = { version = "0.3.4", features = ["html_reports"] }
 name = "addictive_addition"
 harness = false
 
+[[bench]]
+name = "fibonacci"
+harness = false
+
 [[test]]
 name = "logic_and"
 path = "tests/logic/and.rs"

dust-lang/benches/addictive_addition.rs

@@ -3,7 +3,7 @@ use std::time::Duration;
 use criterion::{black_box, criterion_group, criterion_main, Criterion};
 use dust_lang::run;
 
-const SOURCE: &str = "
+const SOURCE: &str = r"
     let mut i = 0
 
     while i < 5_000_000 {

dust-lang/benches/fibonacci.rs

@@ -0,0 +1,32 @@
+use std::time::Duration;
+
+use criterion::{black_box, criterion_group, criterion_main, Criterion};
+use dust_lang::run;
+
+const SOURCE: &str = r"
+    fn fib (n: int) -> int {
+        if n <= 0 { return 0 }
+        if n == 1 { return 1 }
+
+        fib(n - 1) + fib(n - 2)
+    }
+
+    fib(25)
+";
+
+fn addictive_addition(source: &str) {
+    let _ = run(source).unwrap();
+}
+
+fn criterion_benchmark(c: &mut Criterion) {
+    let mut group = c.benchmark_group("fibonacci");
+
+    group.measurement_time(Duration::from_secs(15));
+    group.bench_function("fibonacci", |b| {
+        b.iter(|| addictive_addition(black_box(SOURCE)))
+    });
+    group.finish();
+}
+
+criterion_group!(benches, criterion_benchmark);
+criterion_main!(benches);

dust-lang/src/chunk/disassembler.rs

@@ -407,10 +407,10 @@ impl<'a, W: Write> Disassembler<'a, W> {
 
         let info_line = format!(
             "{} instructions, {} constants, {} locals, returns {}",
-            self.chunk.len(),
+            self.chunk.instructions.len(),
-            self.chunk.constants().len(),
+            self.chunk.constants.len(),
-            self.chunk.locals().len(),
+            self.chunk.locals.len(),
-            self.chunk.r#type().return_type
+            self.chunk.r#type.return_type
         );
 
         self.write_centered_with_border_dim(&info_line)?;

dust-lang/src/chunk/mod.rs

@@ -30,22 +30,29 @@ pub struct Chunk {
     instructions: SmallVec<[(Instruction, Span); 32]>,
     constants: SmallVec<[ConcreteValue; 16]>,
     locals: SmallVec<[Local; 8]>,
+
+    stack_size: usize,
 }
 
 impl Chunk {
-    pub fn new(name: Option<DustString>) -> Self {
+    pub fn new(
+        name: Option<DustString>,
+        r#type: FunctionType,
+        instructions: SmallVec<[(Instruction, Span); 32]>,
+        constants: SmallVec<[ConcreteValue; 16]>,
+        locals: SmallVec<[Local; 8]>,
+        stack_size: usize,
+    ) -> Self {
         Self {
             name,
-            instructions: SmallVec::new(),
+            r#type,
-            constants: SmallVec::new(),
+            instructions,
-            locals: SmallVec::new(),
+            constants,
-            r#type: FunctionType {
+            locals,
-                type_parameters: None,
+            stack_size,
-                value_parameters: None,
-                return_type: Type::None,
-            },
         }
     }
+
     pub fn with_data(
         name: Option<DustString>,
         r#type: FunctionType,
@@ -59,6 +66,7 @@ impl Chunk {
             instructions: instructions.into(),
             constants: constants.into(),
             locals: locals.into(),
+            stack_size: 0,
         }
     }
 
@@ -70,10 +78,6 @@ impl Chunk {
         &self.r#type
     }
 
-    pub fn len(&self) -> usize {
-        self.instructions.len()
-    }
-
     pub fn is_empty(&self) -> bool {
         self.instructions.is_empty()
     }
@@ -91,21 +95,10 @@ impl Chunk {
     }
 
     pub fn stack_size(&self) -> usize {
-        self.instructions()
+        self.stack_size
-            .iter()
-            .rev()
-            .filter_map(|(instruction, _)| {
-                if instruction.yields_value() {
-                    Some(instruction.a as usize + 1)
-                } else {
-                    None
-                }
-            })
-            .max()
-            .unwrap_or(0)
     }
 
-    pub fn disassembler<'a, W: Write>(&'a self, writer: &'a mut W) -> Disassembler<W> {
+    pub fn disassembler<'a, W: Write>(&'a self, writer: &'a mut W) -> Disassembler<'a, W> {
         Disassembler::new(self, writer)
     }
 }

dust-lang/src/compiler/mod.rs

@@ -60,6 +60,7 @@ pub struct Compiler<'src> {
     instructions: SmallVec<[(Instruction, Type, Span); 32]>,
     constants: SmallVec<[ConcreteValue; 16]>,
     locals: SmallVec<[(Local, Type); 8]>,
+    stack_size: usize,
 
     lexer: Lexer<'src>,
 
@@ -89,6 +90,7 @@ impl<'src> Compiler<'src> {
             instructions: SmallVec::new(),
             constants: SmallVec::new(),
             locals: SmallVec::new(),
+            stack_size: 0,
             lexer,
             current_token,
             current_position,
@@ -124,7 +126,14 @@ impl<'src> Compiler<'src> {
             .map(|(local, _)| local)
             .collect::<SmallVec<[Local; 8]>>();
 
-        Chunk::with_data(self.self_name, r#type, instructions, self.constants, locals)
+        Chunk::new(
+            self.self_name,
+            r#type,
+            instructions,
+            self.constants,
+            locals,
+            self.stack_size,
+        )
     }
 
     pub fn compile(&mut self) -> Result<(), CompileError> {
@@ -151,7 +160,7 @@ impl<'src> Compiler<'src> {
             .rev()
             .find_map(|(instruction, _, _)| {
                 if instruction.yields_value() {
-                    Some(instruction.a + 1)
+                    Some(instruction.a_field() + 1)
                 } else {
                     None
                 }
@@ -381,6 +390,12 @@ impl<'src> Compiler<'src> {
             position.to_string()
         );
 
+        if instruction.yields_value() {
+            let destination = instruction.a_field() as usize;
+
+            self.stack_size = (destination + 1).max(self.stack_size);
+        }
+
         self.instructions.push((instruction, r#type, position));
     }
 
@@ -597,9 +612,9 @@ impl<'src> Compiler<'src> {
         instruction: &Instruction,
     ) -> Result<(Argument, bool), CompileError> {
         let (argument, push_back) = match instruction.operation() {
-            Operation::LoadConstant => (Argument::Constant(instruction.b), false),
+            Operation::LoadConstant => (Argument::Constant(instruction.b_field()), false),
             Operation::GetLocal => {
-                let local_index = instruction.b;
+                let local_index = instruction.b_field();
                 let (local, _) = self.get_local(local_index)?;
 
                 (Argument::Register(local.register_index), false)
@@ -617,12 +632,12 @@ impl<'src> Compiler<'src> {
             | Operation::LessEqual
             | Operation::Negate
             | Operation::Not
-            | Operation::Call => (Argument::Register(instruction.a), true),
+            | Operation::Call => (Argument::Register(instruction.a_field()), true),
             Operation::CallNative => {
-                let function = NativeFunction::from(instruction.b);
+                let function = NativeFunction::from(instruction.b_field());
 
                 if function.returns_value() {
-                    (Argument::Register(instruction.a), true)
+                    (Argument::Register(instruction.a_field()), true)
                 } else {
                     return Err(CompileError::ExpectedExpression {
                         found: self.previous_token.to_owned(),
@@ -882,9 +897,9 @@ impl<'src> Compiler<'src> {
                 .iter()
                 .rev()
                 .nth(2)
-                .map_or(0, |(instruction, _, _)| instruction.a);
+                .map_or(0, |(instruction, _, _)| instruction.a_field());
 
-            left_instruction.a = destination;
+            left_instruction.set_a_field(destination);
         }
 
         let jump_index = self.instructions.len().saturating_sub(1);
@@ -932,7 +947,7 @@ impl<'src> Compiler<'src> {
         self.parse_sub_expression(&rule.precedence)?;
 
         let (mut right_instruction, _, _) = self.instructions.last_mut().unwrap();
-        right_instruction.a = left_instruction.a;
+        right_instruction.set_a_field(left_instruction.a_field());
 
         if is_logic_chain {
             let expression_length = self.instructions.len() - jump_index - 1;
@@ -1005,11 +1020,11 @@ impl<'src> Compiler<'src> {
             if self
                 .instructions
                 .last()
-                .map_or(false, |(instruction, _, _)| instruction.is_math())
+                .is_some_and(|(instruction, _, _)| instruction.is_math())
             {
                 let (math_instruction, _, _) = self.instructions.last_mut().unwrap();
 
-                math_instruction.a = local_register_index;
+                math_instruction.set_a_field(local_register_index);
             } else {
                 let register = self.next_register() - 1;
                 let set_local = Instruction::from(SetLocal {
@@ -1194,7 +1209,7 @@ impl<'src> Compiler<'src> {
                 {
                     let (mut loader, _, _) = self.instructions.last_mut().unwrap();
 
-                    loader.c = true as u8;
+                    loader.set_c_field(true as u8);
                 } else {
                     if_block_distance += 1;
                     let jump = Instruction::from(Jump {

dust-lang/src/compiler/optimize.rs

@@ -40,8 +40,8 @@ pub fn optimize_test_with_explicit_booleans(compiler: &mut Compiler) {
 
         let first_loader = compiler.instructions.iter().nth_back(1).unwrap();
         let second_loader = compiler.instructions.last().unwrap();
-        let first_boolean = first_loader.0.b != 0;
+        let first_boolean = first_loader.0.b_field() != 0;
-        let second_boolean = second_loader.0.b != 0;
+        let second_boolean = second_loader.0.b_field() != 0;
 
         if first_boolean && !second_boolean {
             compiler.instructions.pop();
@@ -83,10 +83,10 @@ pub fn optimize_test_with_loader_arguments(compiler: &mut Compiler) {
 
     let first_loader = &mut compiler.instructions.iter_mut().nth_back(1).unwrap().0;
 
-    first_loader.c = true as u8;
+    first_loader.set_c_field(true as u8);
 
-    let first_loader_destination = first_loader.a;
+    let first_loader_destination = first_loader.a_field();
     let second_loader = &mut compiler.instructions.last_mut().unwrap().0;
 
-    second_loader.a = first_loader_destination;
+    second_loader.set_a_field(first_loader_destination);
 }

dust-lang/src/instruction/add.rs

@@ -8,7 +8,7 @@ pub struct Add {
 
 impl From<&Instruction> for Add {
     fn from(instruction: &Instruction) -> Self {
-        let destination = instruction.a;
+        let destination = instruction.a_field();
         let (left, right) = instruction.b_and_c_as_arguments();
 
         Add {
@@ -23,10 +23,9 @@ impl From<Add> for Instruction {
     fn from(add: Add) -> Self {
         let operation = Operation::Add;
         let a = add.destination;
-        let (b, b_options) = add.left.as_index_and_b_options();
+        let (b, b_is_constant) = add.left.as_index_and_constant_flag();
-        let (c, c_options) = add.right.as_index_and_c_options();
+        let (c, c_is_constant) = add.right.as_index_and_constant_flag();
-        let metadata = operation as u8 | b_options.bits() | c_options.bits();
 
-        Instruction { metadata, a, b, c }
+        Instruction::new(operation, a, b, c, b_is_constant, c_is_constant, false)
     }
 }

dust-lang/src/instruction/call.rs

@@ -8,9 +8,9 @@ pub struct Call {
 
 impl From<&Instruction> for Call {
     fn from(instruction: &Instruction) -> Self {
-        let destination = instruction.a;
+        let destination = instruction.a_field();
         let function = instruction.b_as_argument();
-        let argument_count = instruction.c;
+        let argument_count = instruction.c_field();
 
         Call {
             destination,
@@ -23,10 +23,9 @@ impl From<&Instruction> for Call {
 impl From<Call> for Instruction {
     fn from(call: Call) -> Self {
         let a = call.destination;
-        let (b, b_options) = call.function.as_index_and_b_options();
+        let (b, b_is_constant) = call.function.as_index_and_constant_flag();
         let c = call.argument_count;
-        let metadata = Operation::Call as u8 | b_options.bits();
 
-        Instruction { metadata, a, b, c }
+        Instruction::new(Operation::Call, a, b, c, b_is_constant, false, false)
     }
 }

dust-lang/src/instruction/call_native.rs

@@ -8,24 +8,24 @@ pub struct CallNative {
 
 impl From<&Instruction> for CallNative {
     fn from(instruction: &Instruction) -> Self {
-        let destination = instruction.a;
+        let destination = instruction.a_field();
-        let function = NativeFunction::from(instruction.b);
+        let function = NativeFunction::from(instruction.b_field());
 
         CallNative {
             destination,
             function,
-            argument_count: instruction.c,
+            argument_count: instruction.c_field(),
         }
     }
 }
 
 impl From<CallNative> for Instruction {
     fn from(call_native: CallNative) -> Self {
-        let metadata = Operation::CallNative as u8;
+        let operation = Operation::CallNative;
         let a = call_native.destination;
         let b = call_native.function as u8;
         let c = call_native.argument_count;
 
-        Instruction { metadata, a, b, c }
+        Instruction::new(operation, a, b, c, false, false, false)
     }
 }

dust-lang/src/instruction/close.rs

@@ -8,17 +8,17 @@ pub struct Close {
 impl From<&Instruction> for Close {
     fn from(instruction: &Instruction) -> Self {
         Close {
-            from: instruction.b,
+            from: instruction.b_field(),
-            to: instruction.c,
+            to: instruction.c_field(),
         }
     }
 }
 
 impl From<Close> for Instruction {
     fn from(close: Close) -> Self {
-        let metadata = Operation::Close as u8;
+        let operation = Operation::Close;
         let (a, b, c) = (0, close.from, close.to);
 
-        Instruction { metadata, a, b, c }
+        Instruction::new(operation, a, b, c, false, false, false)
     }
 }

dust-lang/src/instruction/divide.rs

@@ -8,7 +8,7 @@ pub struct Divide {
 
 impl From<&Instruction> for Divide {
     fn from(instruction: &Instruction) -> Self {
-        let destination = instruction.a;
+        let destination = instruction.a_field();
         let (left, right) = instruction.b_and_c_as_arguments();
 
         Divide {
@@ -21,11 +21,11 @@ impl From<&Instruction> for Divide {
 
 impl From<Divide> for Instruction {
     fn from(divide: Divide) -> Self {
+        let operation = Operation::Divide;
         let a = divide.destination;
-        let (b, b_options) = divide.left.as_index_and_b_options();
+        let (b, b_is_constant) = divide.left.as_index_and_constant_flag();
-        let (c, c_options) = divide.right.as_index_and_c_options();
+        let (c, c_is_constant) = divide.right.as_index_and_constant_flag();
-        let metadata = Operation::Divide as u8 | b_options.bits() | c_options.bits();
 
-        Instruction { metadata, a, b, c }
+        Instruction::new(operation, a, b, c, b_is_constant, c_is_constant, false)
     }
 }

dust-lang/src/instruction/equal.rs

@@ -1,7 +1,5 @@
 use crate::{Argument, Instruction, Operation};
 
-use super::InstructionOptions;
-
 pub struct Equal {
     pub destination: u8,
     pub value: bool,
@@ -11,8 +9,8 @@ pub struct Equal {
 
 impl From<&Instruction> for Equal {
     fn from(instruction: &Instruction) -> Self {
-        let destination = instruction.a;
+        let destination = instruction.a_field();
-        let value = instruction.d();
+        let value = instruction.d_field();
         let (left, right) = instruction.b_and_c_as_arguments();
 
         Equal {
@@ -26,17 +24,12 @@ impl From<&Instruction> for Equal {
 
 impl From<Equal> for Instruction {
     fn from(equal: Equal) -> Self {
+        let operation = Operation::Equal;
         let a = equal.destination;
-        let (b, b_options) = equal.left.as_index_and_b_options();
+        let (b, b_is_constant) = equal.left.as_index_and_constant_flag();
-        let (c, c_options) = equal.right.as_index_and_c_options();
+        let (c, c_is_constant) = equal.right.as_index_and_constant_flag();
-        let d_options = if equal.value {
+        let d = equal.value;
-            InstructionOptions::D_IS_TRUE
-        } else {
-            InstructionOptions::empty()
-        };
-        let metadata =
-            Operation::Equal as u8 | b_options.bits() | c_options.bits() | d_options.bits();
 
-        Instruction { metadata, a, b, c }
+        Instruction::new(operation, a, b, c, b_is_constant, c_is_constant, d)
     }
 }

dust-lang/src/instruction/get_local.rs

@@ -7,8 +7,8 @@ pub struct GetLocal {
 
 impl From<&Instruction> for GetLocal {
     fn from(instruction: &Instruction) -> Self {
-        let destination = instruction.a;
+        let destination = instruction.a_field();
-        let local_index = instruction.b;
+        let local_index = instruction.b_field();
 
         GetLocal {
             destination,
@@ -19,11 +19,10 @@ impl From<&Instruction> for GetLocal {
 
 impl From<GetLocal> for Instruction {
     fn from(get_local: GetLocal) -> Self {
+        let operation = Operation::GetLocal;
         let a = get_local.destination;
         let b = get_local.local_index;
-        let c = 0;
-        let metadata = Operation::GetLocal as u8;
 
-        Instruction { metadata, a, b, c }
+        Instruction::new(operation, a, b, 0, false, false, false)
     }
 }

dust-lang/src/instruction/jump.rs

@@ -8,19 +8,18 @@ pub struct Jump {
 impl From<&Instruction> for Jump {
     fn from(instruction: &Instruction) -> Self {
         Jump {
-            offset: instruction.b,
+            offset: instruction.b_field(),
-            is_positive: instruction.c != 0,
+            is_positive: instruction.c_field() != 0,
         }
     }
 }
 
 impl From<Jump> for Instruction {
     fn from(jump: Jump) -> Self {
-        let metadata = Operation::Jump as u8;
+        let operation = Operation::Jump;
-        let a = 0;
         let b = jump.offset;
         let c = jump.is_positive as u8;
 
-        Instruction { metadata, a, b, c }
+        Instruction::new(operation, 0, b, c, false, false, false)
     }
 }

dust-lang/src/instruction/less.rs

@@ -1,7 +1,5 @@
 use crate::{Argument, Instruction, Operation};
 
-use super::InstructionOptions;
-
 pub struct Less {
     pub destination: u8,
     pub value: bool,
@@ -11,8 +9,8 @@ pub struct Less {
 
 impl From<&Instruction> for Less {
     fn from(instruction: &Instruction) -> Self {
-        let destination = instruction.a;
+        let destination = instruction.a_field();
-        let value = instruction.d();
+        let value = instruction.d_field();
         let (left, right) = instruction.b_and_c_as_arguments();
 
         Less {
@@ -26,17 +24,12 @@ impl From<&Instruction> for Less {
 
 impl From<Less> for Instruction {
     fn from(less: Less) -> Self {
+        let operation = Operation::Less;
         let a = less.destination;
-        let (b, b_options) = less.left.as_index_and_b_options();
+        let (b, b_is_constant) = less.left.as_index_and_constant_flag();
-        let (c, c_options) = less.right.as_index_and_c_options();
+        let (c, c_is_constant) = less.right.as_index_and_constant_flag();
-        let d_options = if less.value {
+        let d = less.value;
-            InstructionOptions::D_IS_TRUE
-        } else {
-            InstructionOptions::empty()
-        };
-        let metadata =
-            Operation::Less as u8 | b_options.bits() | c_options.bits() | d_options.bits();
 
-        Instruction { metadata, a, b, c }
+        Instruction::new(operation, a, b, c, b_is_constant, c_is_constant, d)
     }
 }

dust-lang/src/instruction/less_equal.rs

@@ -1,7 +1,5 @@
 use crate::{Argument, Instruction, Operation};
 
-use super::InstructionOptions;
-
 pub struct LessEqual {
     pub destination: u8,
     pub value: bool,
@@ -11,8 +9,8 @@ pub struct LessEqual {
 
 impl From<&Instruction> for LessEqual {
     fn from(instruction: &Instruction) -> Self {
-        let destination = instruction.a;
+        let destination = instruction.a_field();
-        let value = instruction.d();
+        let value = instruction.d_field();
         let (left, right) = instruction.b_and_c_as_arguments();
 
         LessEqual {
@@ -26,17 +24,12 @@ impl From<&Instruction> for LessEqual {
 
 impl From<LessEqual> for Instruction {
     fn from(less_equal: LessEqual) -> Self {
+        let operation = Operation::LessEqual;
         let a = less_equal.destination;
-        let (b, b_options) = less_equal.left.as_index_and_b_options();
+        let (b, b_options) = less_equal.left.as_index_and_constant_flag();
-        let (c, c_options) = less_equal.right.as_index_and_c_options();
+        let (c, c_options) = less_equal.right.as_index_and_constant_flag();
-        let d_options = if less_equal.value {
+        let d = less_equal.value;
-            InstructionOptions::D_IS_TRUE
-        } else {
-            InstructionOptions::empty()
-        };
-        let metadata =
-            Operation::LessEqual as u8 | b_options.bits() | c_options.bits() | d_options.bits();
 
-        Instruction { metadata, a, b, c }
+        Instruction::new(operation, a, b, c, b_options, c_options, d)
     }
 }

dust-lang/src/instruction/load_boolean.rs

@@ -8,9 +8,9 @@ pub struct LoadBoolean {
 
 impl From<&Instruction> for LoadBoolean {
     fn from(instruction: &Instruction) -> Self {
-        let destination = instruction.a;
+        let destination = instruction.a_field();
-        let value = instruction.b != 0;
+        let value = instruction.b_field() != 0;
-        let jump_next = instruction.c != 0;
+        let jump_next = instruction.c_field() != 0;
 
         LoadBoolean {
             destination,
@@ -22,11 +22,11 @@ impl From<&Instruction> for LoadBoolean {
 
 impl From<LoadBoolean> for Instruction {
     fn from(load_boolean: LoadBoolean) -> Self {
-        let metadata = Operation::LoadBoolean as u8;
+        let operation = Operation::LoadBoolean;
         let a = load_boolean.destination;
         let b = load_boolean.value as u8;
         let c = load_boolean.jump_next as u8;
 
-        Instruction { metadata, a, b, c }
+        Instruction::new(operation, a, b, c, false, false, false)
     }
 }

dust-lang/src/instruction/load_constant.rs

@@ -8,9 +8,9 @@ pub struct LoadConstant {
 
 impl From<&Instruction> for LoadConstant {
     fn from(instruction: &Instruction) -> Self {
-        let destination = instruction.a;
+        let destination = instruction.a_field();
-        let constant_index = instruction.b;
+        let constant_index = instruction.b_field();
-        let jump_next = instruction.c != 0;
+        let jump_next = instruction.c_field() != 0;
 
         LoadConstant {
             destination,
@@ -22,11 +22,11 @@ impl From<&Instruction> for LoadConstant {
 
 impl From<LoadConstant> for Instruction {
     fn from(load_constant: LoadConstant) -> Self {
-        let metadata = Operation::LoadConstant as u8;
+        let operation = Operation::LoadConstant;
         let a = load_constant.destination;
         let b = load_constant.constant_index;
         let c = load_constant.jump_next as u8;
 
-        Instruction { metadata, a, b, c }
+        Instruction::new(operation, a, b, c, false, false, false)
     }
 }

dust-lang/src/instruction/load_list.rs

@@ -7,8 +7,8 @@ pub struct LoadList {
 
 impl From<&Instruction> for LoadList {
     fn from(instruction: &Instruction) -> Self {
-        let destination = instruction.a;
+        let destination = instruction.a_field();
-        let start_register = instruction.b;
+        let start_register = instruction.b_field();
 
         LoadList {
             destination,
@@ -19,11 +19,10 @@ impl From<&Instruction> for LoadList {
 
 impl From<LoadList> for Instruction {
     fn from(load_list: LoadList) -> Self {
-        let metadata = Operation::LoadList as u8;
+        let operation = Operation::LoadList;
         let a = load_list.destination;
         let b = load_list.start_register;
-        let c = 0;
 
-        Instruction { metadata, a, b, c }
+        Instruction::new(operation, a, b, 0, false, false, false)
     }
 }

dust-lang/src/instruction/load_self.rs

@@ -6,7 +6,7 @@ pub struct LoadSelf {
 
 impl From<&Instruction> for LoadSelf {
     fn from(instruction: &Instruction) -> Self {
-        let destination = instruction.a;
+        let destination = instruction.a_field();
 
         LoadSelf { destination }
     }
@@ -14,11 +14,9 @@ impl From<&Instruction> for LoadSelf {
 
 impl From<LoadSelf> for Instruction {
     fn from(load_self: LoadSelf) -> Self {
-        let metadata = Operation::LoadSelf as u8;
+        let operation = Operation::LoadSelf;
         let a = load_self.destination;
-        let b = 0;
-        let c = 0;
 
-        Instruction { metadata, a, b, c }
+        Instruction::new(operation, a, 0, 0, false, false, false)
     }
 }

dust-lang/src/instruction/mod.rs

@@ -109,7 +109,6 @@ mod multiply;
 mod negate;
 mod not;
 mod operation;
-mod options;
 mod r#return;
 mod set_local;
 mod subtract;
@@ -135,7 +134,6 @@ pub use multiply::Multiply;
 pub use negate::Negate;
 pub use not::Not;
 pub use operation::Operation;
-pub use options::InstructionOptions;
 pub use r#move::Move;
 pub use r#return::Return;
 pub use set_local::SetLocal;
@@ -152,22 +150,92 @@ use crate::NativeFunction;
 ///
 /// See the [module-level documentation](index.html) for more information.
 #[derive(Clone, Copy, Eq, PartialEq, PartialOrd, Ord, Serialize, Deserialize)]
-pub struct Instruction {
+pub struct Instruction(u32);
-    pub metadata: u8,
+
+#[derive(Clone, Copy, Eq, PartialEq, PartialOrd, Ord, Serialize, Deserialize)]
+pub struct InstructionData {
+    pub operation: Operation,
     pub a: u8,
     pub b: u8,
     pub c: u8,
+    pub b_is_constant: bool,
+    pub c_is_constant: bool,
+    pub d: bool,
 }
 
 impl Instruction {
-    pub fn operation(&self) -> Operation {
+    pub fn new(
-        let operation_bits = self.metadata & 0b0001_1111;
+        operation: Operation,
+        a: u8,
+        b: u8,
+        c: u8,
+        b_is_constant: bool,
+        c_is_constant: bool,
+        d: bool,
+    ) -> Instruction {
+        let bits = operation as u32
+            | ((b_is_constant as u32) << 5)
+            | ((c_is_constant as u32) << 6)
+            | ((d as u32) << 7)
+            | ((a as u32) << 8)
+            | ((b as u32) << 16)
+            | ((c as u32) << 24);
 
-        Operation::from(operation_bits)
+        Instruction(bits)
     }
 
-    pub fn d(&self) -> bool {
+    pub fn operation(&self) -> Operation {
-        self.metadata & 0b1000_0000 != 0
+        let operation_bits = self.0 & 0b0001_1111;
+
+        Operation::from(operation_bits as u8)
+    }
+
+    pub fn b_is_constant(&self) -> bool {
+        (self.0 >> 5) & 1 == 1
+    }
+
+    pub fn c_is_constant(&self) -> bool {
+        (self.0 >> 6) & 1 == 1
+    }
+
+    pub fn d_field(&self) -> bool {
+        (self.0 >> 7) & 1 == 1
+    }
+
+    pub fn a_field(&self) -> u8 {
+        (self.0 >> 8) as u8
+    }
+
+    pub fn b_field(&self) -> u8 {
+        (self.0 >> 16) as u8
+    }
+
+    pub fn c_field(&self) -> u8 {
+        (self.0 >> 24) as u8
+    }
+
+    pub fn set_a_field(&mut self, bits: u8) {
+        self.0 = (self.0 & 0xFFFF00FF) | ((bits as u32) << 8);
+    }
+
+    pub fn set_b_field(&mut self, bits: u8) {
+        self.0 = (self.0 & 0xFFFF00FF) | ((bits as u32) << 16);
+    }
+
+    pub fn set_c_field(&mut self, bits: u8) {
+        self.0 = (self.0 & 0xFF00FFFF) | ((bits as u32) << 24);
+    }
+
+    pub fn decode(self) -> InstructionData {
+        InstructionData {
+            operation: self.operation(),
+            a: self.a_field(),
+            b: self.b_field(),
+            c: self.c_field(),
+            b_is_constant: self.b_is_constant(),
+            c_is_constant: self.c_is_constant(),
+            d: self.d_field(),
+        }
     }
 
     pub fn r#move(from: u8, to: u8) -> Instruction {
@@ -373,7 +441,7 @@ impl Instruction {
 
     pub fn as_argument(&self) -> Option<Argument> {
         match self.operation() {
-            Operation::LoadConstant => Some(Argument::Constant(self.b)),
+            Operation::LoadConstant => Some(Argument::Constant(self.b_field())),
             Operation::LoadBoolean
             | Operation::LoadList
             | Operation::LoadSelf
@@ -388,12 +456,12 @@ impl Instruction {
             | Operation::LessEqual
             | Operation::Negate
             | Operation::Not
-            | Operation::Call => Some(Argument::Register(self.a)),
+            | Operation::Call => Some(Argument::Register(self.a_field())),
             Operation::CallNative => {
-                let function = NativeFunction::from(self.b);
+                let function = NativeFunction::from(self.b_field());
 
                 if function.returns_value() {
-                    Some(Argument::Register(self.a))
+                    Some(Argument::Register(self.a_field()))
                 } else {
                     None
                 }
@@ -403,28 +471,23 @@ impl Instruction {
     }
 
     pub fn b_as_argument(&self) -> Argument {
-        let b_is_constant = self.metadata & 0b0010_0000 != 0;
+        if self.b_is_constant() {
-
+            Argument::Constant(self.b_field())
-        if b_is_constant {
-            Argument::Constant(self.b)
         } else {
-            Argument::Register(self.b)
+            Argument::Register(self.b_field())
         }
     }
 
     pub fn b_and_c_as_arguments(&self) -> (Argument, Argument) {
-        let b_is_constant = self.metadata & 0b0010_0000 != 0;
+        let left = if self.b_is_constant() {
-        let c_is_constant = self.metadata & 0b0100_0000 != 0;
+            Argument::Constant(self.b_field())
-
-        let left = if b_is_constant {
-            Argument::Constant(self.b)
         } else {
-            Argument::Register(self.b)
+            Argument::Register(self.b_field())
         };
-        let right = if c_is_constant {
+        let right = if self.c_is_constant() {
-            Argument::Constant(self.c)
+            Argument::Constant(self.c_field())
         } else {
-            Argument::Register(self.c)
+            Argument::Register(self.c_field())
         };
 
         (left, right)
@@ -451,7 +514,7 @@ impl Instruction {
             | Operation::LessEqual
             | Operation::Call => true,
             Operation::CallNative => {
-                let function = NativeFunction::from(self.b);
+                let function = NativeFunction::from(self.b_field());
 
                 function.returns_value()
             }
@@ -655,7 +718,7 @@ impl Instruction {
                 if is_positive {
                     format!("JUMP +{offset}")
                 } else {
-                    format!("JUMP -{}", offset - 1)
+                    format!("JUMP -{offset}")
                 }
             }
             Operation::Call => {
@@ -751,17 +814,10 @@ impl Argument {
         matches!(self, Argument::Register(_))
     }
 
-    pub fn as_index_and_b_options(&self) -> (u8, InstructionOptions) {
+    pub fn as_index_and_constant_flag(&self) -> (u8, bool) {
         match self {
-            Argument::Constant(index) => (*index, InstructionOptions::B_IS_CONSTANT),
+            Argument::Constant(index) => (*index, true),
-            Argument::Register(index) => (*index, InstructionOptions::empty()),
+            Argument::Register(index) => (*index, false),
-        }
-    }
-
-    pub fn as_index_and_c_options(&self) -> (u8, InstructionOptions) {
-        match self {
-            Argument::Constant(index) => (*index, InstructionOptions::C_IS_CONSTANT),
-            Argument::Register(index) => (*index, InstructionOptions::empty()),
         }
     }
 }
@@ -774,23 +830,3 @@ impl Display for Argument {
         }
     }
 }
-
-#[cfg(test)]
-mod tests {
-    use std::mem::offset_of;
-
-    use super::*;
-
-    #[test]
-    fn instruction_is_4_bytes() {
-        assert_eq!(size_of::<Instruction>(), 4);
-    }
-
-    #[test]
-    fn instruction_layout() {
-        assert_eq!(offset_of!(Instruction, metadata), 0);
-        assert_eq!(offset_of!(Instruction, a), 1);
-        assert_eq!(offset_of!(Instruction, b), 2);
-        assert_eq!(offset_of!(Instruction, c), 3);
-    }
-}

dust-lang/src/instruction/modulo.rs

@@ -8,7 +8,7 @@ pub struct Modulo {
 
 impl From<&Instruction> for Modulo {
     fn from(instruction: &Instruction) -> Self {
-        let destination = instruction.a;
+        let destination = instruction.a_field();
         let (left, right) = instruction.b_and_c_as_arguments();
 
         Modulo {
@@ -21,11 +21,11 @@ impl From<&Instruction> for Modulo {
 
 impl From<Modulo> for Instruction {
     fn from(modulo: Modulo) -> Self {
+        let operation = Operation::Modulo;
         let a = modulo.destination;
-        let (b, b_options) = modulo.left.as_index_and_b_options();
+        let (b, b_is_constant) = modulo.left.as_index_and_constant_flag();
-        let (c, c_options) = modulo.right.as_index_and_c_options();
+        let (c, c_is_constant) = modulo.right.as_index_and_constant_flag();
-        let metadata = Operation::Modulo as u8 | b_options.bits() | c_options.bits();
 
-        Instruction { metadata, a, b, c }
+        Instruction::new(operation, a, b, c, b_is_constant, c_is_constant, false)
     }
 }

dust-lang/src/instruction/move.rs

@@ -8,19 +8,18 @@ pub struct Move {
 impl From<&Instruction> for Move {
     fn from(instruction: &Instruction) -> Self {
         Move {
-            from: instruction.b,
+            from: instruction.b_field(),
-            to: instruction.c,
+            to: instruction.c_field(),
         }
     }
 }
 
 impl From<Move> for Instruction {
     fn from(r#move: Move) -> Self {
-        let metadata = Operation::Move as u8;
+        let operation = Operation::Move;
-        let a = 0;
         let b = r#move.from;
         let c = r#move.to;
 
-        Instruction { metadata, a, b, c }
+        Instruction::new(operation, 0, b, c, false, false, false)
     }
 }

dust-lang/src/instruction/multiply.rs

@@ -8,7 +8,7 @@ pub struct Multiply {
 
 impl From<&Instruction> for Multiply {
     fn from(instruction: &Instruction) -> Self {
-        let destination = instruction.a;
+        let destination = instruction.a_field();
         let (left, right) = instruction.b_and_c_as_arguments();
 
         Multiply {
@@ -21,11 +21,11 @@ impl From<&Instruction> for Multiply {
 
 impl From<Multiply> for Instruction {
     fn from(multiply: Multiply) -> Self {
+        let operation = Operation::Multiply;
         let a = multiply.destination;
-        let (b, b_options) = multiply.left.as_index_and_b_options();
+        let (b, b_options) = multiply.left.as_index_and_constant_flag();
-        let (c, c_options) = multiply.right.as_index_and_c_options();
+        let (c, c_options) = multiply.right.as_index_and_constant_flag();
-        let metadata = Operation::Multiply as u8 | b_options.bits() | c_options.bits();
 
-        Instruction { metadata, a, b, c }
+        Instruction::new(operation, a, b, c, b_options, c_options, false)
     }
 }

dust-lang/src/instruction/negate.rs

@@ -7,7 +7,7 @@ pub struct Negate {
 
 impl From<&Instruction> for Negate {
     fn from(instruction: &Instruction) -> Self {
-        let destination = instruction.a;
+        let destination = instruction.a_field();
         let argument = instruction.b_as_argument();
 
         Negate {
@@ -19,11 +19,11 @@ impl From<&Instruction> for Negate {
 
 impl From<Negate> for Instruction {
     fn from(negate: Negate) -> Self {
+        let operation = Operation::Negate;
         let a = negate.destination;
-        let (b, b_options) = negate.argument.as_index_and_b_options();
+        let (b, b_is_constant) = negate.argument.as_index_and_constant_flag();
         let c = 0;
-        let metadata = Operation::Negate as u8 | b_options.bits();
 
-        Instruction { metadata, a, b, c }
+        Instruction::new(operation, a, b, c, b_is_constant, false, false)
     }
 }

dust-lang/src/instruction/not.rs

@@ -7,7 +7,7 @@ pub struct Not {
 
 impl From<&Instruction> for Not {
     fn from(instruction: &Instruction) -> Self {
-        let destination = instruction.a;
+        let destination = instruction.a_field();
         let argument = instruction.b_as_argument();
 
         Not {
@@ -19,11 +19,10 @@ impl From<&Instruction> for Not {
 
 impl From<Not> for Instruction {
     fn from(not: Not) -> Self {
+        let operation = Operation::Not;
         let a = not.destination;
-        let (b, b_options) = not.argument.as_index_and_b_options();
+        let (b, b_is_constant) = not.argument.as_index_and_constant_flag();
-        let c = 0;
-        let metadata = Operation::Not as u8 | b_options.bits();
 
-        Instruction { metadata, a, b, c }
+        Instruction::new(operation, a, b, 0, b_is_constant, false, false)
     }
 }

dust-lang/src/instruction/options.rs

@@ -1,34 +0,0 @@
-//! Byte that uses its bits as boolean flags to represent information about an instruction's
-//! arguments. Additionally, one bit is used as the instruction's `D` field.
-//!
-//! See the [instruction documentation](crate::instruction) for more information.
-use bitflags::bitflags;
-use serde::{Deserialize, Serialize};
-
-bitflags! {
-    /// Byte that uses its bits as boolean flags to represent an instruction's options and D field.
-    ///
-    /// See the [instruction documentation](crate::instruction) for more information.
-    #[derive(Clone, Copy, Eq, PartialEq, PartialOrd, Ord, Serialize, Deserialize)]
-    pub struct InstructionOptions: u8 {
-        const B_IS_CONSTANT = 0b0010_0000;
-
-        const C_IS_CONSTANT = 0b0100_0000;
-
-        const D_IS_TRUE = 0b1000_0000;
-    }
-}
-
-impl InstructionOptions {
-    pub fn b_is_constant(self) -> bool {
-        self.contains(Self::B_IS_CONSTANT)
-    }
-
-    pub fn c_is_constant(self) -> bool {
-        self.contains(Self::C_IS_CONSTANT)
-    }
-
-    pub fn d(self) -> bool {
-        self.contains(Self::D_IS_TRUE)
-    }
-}

dust-lang/src/instruction/return.rs

@@ -6,7 +6,7 @@ pub struct Return {
 
 impl From<&Instruction> for Return {
     fn from(instruction: &Instruction) -> Self {
-        let should_return_value = instruction.b != 0;
+        let should_return_value = instruction.b_field() != 0;
 
         Return {
             should_return_value,
@@ -16,11 +16,9 @@ impl From<&Instruction> for Return {
 
 impl From<Return> for Instruction {
     fn from(r#return: Return) -> Self {
-        let metadata = Operation::Return as u8;
+        let operation = Operation::Return;
-        let a = 0;
         let b = r#return.should_return_value as u8;
-        let c = 0;
 
-        Instruction { metadata, a, b, c }
+        Instruction::new(operation, 0, b, 0, false, false, false)
     }
 }

dust-lang/src/instruction/set_local.rs

@@ -7,8 +7,8 @@ pub struct SetLocal {
 
 impl From<&Instruction> for SetLocal {
     fn from(instruction: &Instruction) -> Self {
-        let register_index = instruction.b;
+        let register_index = instruction.b_field();
-        let local_index = instruction.c;
+        let local_index = instruction.c_field();
 
         SetLocal {
             register_index,
@@ -19,11 +19,10 @@ impl From<&Instruction> for SetLocal {
 
 impl From<SetLocal> for Instruction {
     fn from(set_local: SetLocal) -> Self {
-        let metadata = Operation::SetLocal as u8;
+        let operation = Operation::SetLocal;
-        let a = 0;
         let b = set_local.register_index;
         let c = set_local.local_index;
 
-        Instruction { metadata, a, b, c }
+        Instruction::new(operation, 0, b, c, false, false, false)
     }
 }

dust-lang/src/instruction/subtract.rs

@@ -8,7 +8,7 @@ pub struct Subtract {
 
 impl From<&Instruction> for Subtract {
     fn from(instruction: &Instruction) -> Self {
-        let destination = instruction.a;
+        let destination = instruction.a_field();
         let (left, right) = instruction.b_and_c_as_arguments();
 
         Subtract {
@@ -21,11 +21,11 @@ impl From<&Instruction> for Subtract {
 
 impl From<Subtract> for Instruction {
     fn from(subtract: Subtract) -> Self {
+        let operation = Operation::Subtract;
         let a = subtract.destination;
-        let (b, b_options) = subtract.left.as_index_and_b_options();
+        let (b, b_is_constant) = subtract.left.as_index_and_constant_flag();
-        let (c, c_options) = subtract.right.as_index_and_c_options();
+        let (c, c_is_constant) = subtract.right.as_index_and_constant_flag();
-        let metadata = Operation::Subtract as u8 | b_options.bits() | c_options.bits();
 
-        Instruction { metadata, a, b, c }
+        Instruction::new(operation, a, b, c, b_is_constant, c_is_constant, false)
     }
 }

dust-lang/src/instruction/test.rs

@@ -8,7 +8,7 @@ pub struct Test {
 impl From<&Instruction> for Test {
     fn from(instruction: &Instruction) -> Self {
         let argument = instruction.b_as_argument();
-        let test_value = instruction.c != 0;
+        let test_value = instruction.c_field() != 0;
 
         Test {
             argument,
@@ -19,11 +19,10 @@ impl From<&Instruction> for Test {
 
 impl From<Test> for Instruction {
     fn from(test: Test) -> Self {
-        let a = 0;
+        let operation = Operation::Test;
-        let (b, options) = test.argument.as_index_and_b_options();
+        let (b, b_is_constant) = test.argument.as_index_and_constant_flag();
         let c = test.test_value as u8;
-        let metadata = Operation::Test as u8 | options.bits();
 
-        Instruction { metadata, a, b, c }
+        Instruction::new(operation, 0, b, c, b_is_constant, false, false)
     }
 }

dust-lang/src/instruction/test_set.rs

@@ -8,9 +8,9 @@ pub struct TestSet {
 
 impl From<&Instruction> for TestSet {
     fn from(instruction: &Instruction) -> Self {
-        let destination = instruction.a;
+        let destination = instruction.a_field();
         let argument = instruction.b_as_argument();
-        let test_value = instruction.c != 0;
+        let test_value = instruction.c_field() != 0;
 
         TestSet {
             destination,
@@ -22,11 +22,11 @@ impl From<&Instruction> for TestSet {
 
 impl From<TestSet> for Instruction {
     fn from(test_set: TestSet) -> Self {
+        let operation = Operation::Test;
         let a = test_set.destination;
-        let (b, b_options) = test_set.argument.as_index_and_b_options();
+        let (b, b_is_constant) = test_set.argument.as_index_and_constant_flag();
         let c = test_set.test_value as u8;
-        let metadata = Operation::TestSet as u8 | b_options.bits();
 
-        Instruction { metadata, a, b, c }
+        Instruction::new(operation, a, b, c, b_is_constant, false, false)
     }
 }

dust-lang/src/lexer.rs

@@ -619,7 +619,7 @@ pub struct LexRule<'src> {
     lexer: LexerFn<'src>,
 }
 
-impl<'src> From<&char> for LexRule<'src> {
+impl From<&char> for LexRule<'_> {
     fn from(char: &char) -> Self {
         match char {
             '0'..='9' => LexRule {

dust-lang/src/lib.rs

@@ -42,7 +42,7 @@ pub mod vm;
 pub use crate::chunk::{Chunk, Disassembler, Local, Scope};
 pub use crate::compiler::{compile, CompileError, Compiler};
 pub use crate::dust_error::{AnnotatedError, DustError};
-pub use crate::instruction::{Argument, Instruction, Operation};
+pub use crate::instruction::{Argument, Instruction, InstructionData, Operation};
 pub use crate::lexer::{lex, LexError, Lexer};
 pub use crate::native_function::{NativeFunction, NativeFunctionError};
 pub use crate::r#type::{EnumType, FunctionType, StructType, Type, TypeConflict};

dust-lang/src/token.rs

@@ -93,7 +93,7 @@ define_tokens! {
     StarEqual,
 }
 
-impl<'src> Token<'src> {
+impl Token<'_> {
     #[allow(clippy::len_without_is_empty)]
     pub fn len(&self) -> usize {
         match self {
@@ -382,7 +382,7 @@ impl<'src> Token<'src> {
     }
 }
 
-impl<'src> Display for Token<'src> {
+impl Display for Token<'_> {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         match self {
             Token::ArrowThin => write!(f, "->"),

dust-lang/src/vm.rs

@@ -4,12 +4,11 @@ use std::{
     io,
 };
 
-use slab::Slab;
 use smallvec::SmallVec;
 
 use crate::{
-    compile, instruction::*, AbstractValue, AnnotatedError, Argument, Chunk, ConcreteValue,
+    compile, instruction::*, AbstractValue, AnnotatedError, Chunk, ConcreteValue, DustError,
-    DustError, Instruction, NativeFunctionError, Operation, Span, Value, ValueError, ValueRef,
+    Instruction, NativeFunctionError, Operation, Span, Value, ValueError, ValueRef,
 };
 
 pub fn run(source: &str) -> Result<Option<ConcreteValue>, DustError> {
@@ -24,7 +23,7 @@ pub fn run(source: &str) -> Result<Option<ConcreteValue>, DustError> {
 /// See the [module-level documentation](index.html) for more information.
 #[derive(Debug)]
 pub struct Vm<'a> {
-    stack: Slab<Register>,
+    stack: Vec<Register>,
 
     chunk: &'a Chunk,
     parent: Option<&'a Vm<'a>>,
@@ -36,11 +35,7 @@ pub struct Vm<'a> {
 
 impl<'a> Vm<'a> {
     pub fn new(source: &'a str, chunk: &'a Chunk, parent: Option<&'a Vm<'a>>) -> Self {
-        let mut stack = Slab::with_capacity(chunk.stack_size());
+        let stack = vec![Register::Empty; chunk.stack_size()];
-
-        for _ in 0..chunk.stack_size() {
-            stack.insert(Register::Empty);
-        }
 
         Self {
             chunk,
@@ -70,6 +65,15 @@ impl<'a> Vm<'a> {
     pub fn run(&mut self) -> Result<Option<ConcreteValue>, VmError> {
         loop {
             let instruction = self.read();
+            let InstructionData {
+                operation,
+                a,
+                b,
+                c,
+                b_is_constant,
+                c_is_constant,
+                d,
+            } = instruction.decode();
 
             log::info!(
                 "{} | {} | {} | {}",
@@ -79,7 +83,7 @@ impl<'a> Vm<'a> {
                 instruction.disassembly_info()
             );
 
-            match instruction.operation() {
+            match operation {
                 Operation::Move => {
                     let Move { from, to } = Move::from(&instruction);
                     let from_register_has_value = self
@@ -121,16 +125,11 @@ impl<'a> Vm<'a> {
                     }
                 }
                 Operation::LoadConstant => {
-                    let LoadConstant {
+                    let register = Register::Pointer(Pointer::Constant(b));
-                        destination,
-                        constant_index,
-                        jump_next,
-                    } = LoadConstant::from(&instruction);
-                    let register = Register::Pointer(Pointer::Constant(constant_index));
 
-                    self.set_register(destination, register)?;
+                    self.set_register(a, register)?;
 
-                    if jump_next {
+                    if c != 0 {
                         self.jump(1, true);
                     }
                 }
@@ -187,13 +186,16 @@ impl<'a> Vm<'a> {
                     self.set_register(local_register_index, register)?;
                 }
                 Operation::Add => {
-                    let Add {
+                    let left = if b_is_constant {
-                        destination,
+                        self.get_constant(b).to_value_ref()
-                        left,
+                    } else {
-                        right,
+                        self.open_register(b)?
-                    } = Add::from(&instruction);
+                    };
-                    let left = self.get_argument(left)?;
+                    let right = if c_is_constant {
-                    let right = self.get_argument(right)?;
+                        self.get_constant(c).to_value_ref()
+                    } else {
+                        self.open_register(c)?
+                    };
                     let sum_result = left.add(right);
                     let sum = match sum_result {
                         Ok(sum) => sum,
@@ -205,16 +207,11 @@ impl<'a> Vm<'a> {
                         }
                     };
 
-                    self.set_register(destination, Register::Value(sum))?;
+                    self.set_register(a, Register::Value(sum))?;
                 }
                 Operation::Subtract => {
-                    let Subtract {
+                    let left = self.get_argument(b, b_is_constant)?;
-                        destination,
+                    let right = self.get_argument(c, c_is_constant)?;
-                        left,
-                        right,
-                    } = Subtract::from(&instruction);
-                    let left = self.get_argument(left)?;
-                    let right = self.get_argument(right)?;
                     let subtraction_result = left.subtract(right);
                     let difference = match subtraction_result {
                         Ok(difference) => difference,
@@ -226,16 +223,11 @@ impl<'a> Vm<'a> {
                         }
                     };
 
-                    self.set_register(destination, Register::Value(difference))?;
+                    self.set_register(a, Register::Value(difference))?;
                 }
                 Operation::Multiply => {
-                    let Multiply {
+                    let left = self.get_argument(b, b_is_constant)?;
-                        destination,
+                    let right = self.get_argument(c, c_is_constant)?;
-                        left,
-                        right,
-                    } = Multiply::from(&instruction);
-                    let left = self.get_argument(left)?;
-                    let right = self.get_argument(right)?;
                     let multiplication_result = left.multiply(right);
                     let product = match multiplication_result {
                         Ok(product) => product,
@@ -247,7 +239,7 @@ impl<'a> Vm<'a> {
                         }
                     };
 
-                    self.set_register(destination, Register::Value(product))?;
+                    self.set_register(a, Register::Value(product))?;
                 }
                 Operation::Divide => {
                     let Divide {
@@ -255,8 +247,8 @@ impl<'a> Vm<'a> {
                         left,
                         right,
                     } = Divide::from(&instruction);
-                    let left = self.get_argument(left)?;
+                    let left = self.get_argument(b, b_is_constant)?;
-                    let right = self.get_argument(right)?;
+                    let right = self.get_argument(c, c_is_constant)?;
                     let division_result = left.divide(right);
                     let quotient = match division_result {
                         Ok(quotient) => quotient,
@@ -276,8 +268,8 @@ impl<'a> Vm<'a> {
                         left,
                         right,
                     } = Modulo::from(&instruction);
-                    let left = self.get_argument(left)?;
+                    let left = self.get_argument(b, b_is_constant)?;
-                    let right = self.get_argument(right)?;
+                    let right = self.get_argument(c, c_is_constant)?;
                     let modulo_result = left.modulo(right);
                     let remainder = match modulo_result {
                         Ok(remainder) => remainder,
@@ -292,11 +284,11 @@ impl<'a> Vm<'a> {
                     self.set_register(destination, Register::Value(remainder))?;
                 }
                 Operation::Test => {
-                    let Test {
+                    let value = if b_is_constant {
-                        argument,
+                        self.get_constant(b).to_value_ref()
-                        test_value,
+                    } else {
-                    } = Test::from(&instruction);
+                        self.open_register(b)?
-                    let value = self.get_argument(argument)?;
+                    };
                     let boolean = if let ValueRef::Concrete(ConcreteValue::Boolean(boolean)) = value
                     {
                         *boolean
@@ -307,17 +299,12 @@ impl<'a> Vm<'a> {
                         });
                     };
 
-                    if boolean == test_value {
+                    if boolean == (c != 0) {
                         self.jump(1, true);
                     }
                 }
                 Operation::TestSet => {
-                    let TestSet {
+                    let value = self.get_argument(b, b_is_constant)?;
-                        destination,
-                        argument,
-                        test_value,
-                    } = TestSet::from(&instruction);
-                    let value = self.get_argument(argument)?;
                     let boolean = if let ValueRef::Concrete(ConcreteValue::Boolean(boolean)) = value
                     {
                         *boolean
@@ -327,28 +314,24 @@ impl<'a> Vm<'a> {
                             position: self.current_position(),
                         });
                     };
+                    let test_value = c != 0;
 
                     if boolean == test_value {
                         self.jump(1, true);
                     } else {
-                        let pointer = match argument {
+                        let pointer = if b_is_constant {
-                            Argument::Constant(constant_index) => Pointer::Constant(constant_index),
+                            Pointer::Constant(b)
-                            Argument::Register(register_index) => Pointer::Stack(register_index),
+                        } else {
+                            Pointer::Stack(b)
                         };
                         let register = Register::Pointer(pointer);
 
-                        self.set_register(destination, register)?;
+                        self.set_register(a, register)?;
                     }
                 }
                 Operation::Equal => {
-                    let Equal {
+                    let left = self.get_argument(b, b_is_constant)?;
-                        destination,
+                    let right = self.get_argument(c, c_is_constant)?;
-                        value,
-                        left,
-                        right,
-                    } = Equal::from(&instruction);
-                    let left = self.get_argument(left)?;
-                    let right = self.get_argument(right)?;
                     let equal_result = left.equal(right).map_err(|error| VmError::Value {
                         error,
                         position: self.current_position(),
@@ -362,21 +345,23 @@ impl<'a> Vm<'a> {
                                 position: self.current_position(),
                             });
                         };
-                    let comparison = is_equal == value;
+                    let comparison = is_equal == d;
                     let register =
                         Register::Value(Value::Concrete(ConcreteValue::Boolean(comparison)));
 
-                    self.set_register(destination, register)?;
+                    self.set_register(a, register)?;
                 }
                 Operation::Less => {
-                    let Less {
+                    let left = if b_is_constant {
-                        destination,
+                        self.get_constant(b).to_value_ref()
-                        value,
+                    } else {
-                        left,
+                        self.open_register(b)?
-                        right,
+                    };
-                    } = Less::from(&instruction);
+                    let right = if c_is_constant {
-                    let left = self.get_argument(left)?;
+                        self.get_constant(c).to_value_ref()
-                    let right = self.get_argument(right)?;
+                    } else {
+                        self.open_register(c)?
+                    };
                     let less_result = left.less_than(right);
                     let less_than_value = match less_result {
                         Ok(value) => value,
@@ -396,21 +381,23 @@ impl<'a> Vm<'a> {
                             });
                         }
                     };
-                    let comparison = is_less_than == value;
+                    let comparison = is_less_than == d;
                     let register =
                         Register::Value(Value::Concrete(ConcreteValue::Boolean(comparison)));
 
-                    self.set_register(destination, register)?;
+                    self.set_register(a, register)?;
                 }
                 Operation::LessEqual => {
-                    let LessEqual {
+                    let left = if b_is_constant {
-                        destination,
+                        self.get_constant(b).to_value_ref()
-                        value,
+                    } else {
-                        left,
+                        self.open_register(b)?
-                        right,
+                    };
-                    } = LessEqual::from(&instruction);
+                    let right = if c_is_constant {
-                    let left = self.get_argument(left)?;
+                        self.get_constant(c).to_value_ref()
-                    let right = self.get_argument(right)?;
+                    } else {
+                        self.open_register(c)?
+                    };
                     let less_or_equal_result = left.less_than_or_equal(right);
                     let less_or_equal_value = match less_or_equal_result {
                         Ok(value) => value,
@@ -430,55 +417,37 @@ impl<'a> Vm<'a> {
                             });
                         }
                     };
-                    let comparison = is_less_than_or_equal == value;
+                    let comparison = is_less_than_or_equal == d;
                     let register =
                         Register::Value(Value::Concrete(ConcreteValue::Boolean(comparison)));
 
-                    self.set_register(destination, register)?;
+                    self.set_register(a, register)?;
                 }
                 Operation::Negate => {
-                    let Negate {
+                    let value = self.get_argument(b, b_is_constant)?;
-                        destination,
-                        argument,
-                    } = Negate::from(&instruction);
-                    let value = self.get_argument(argument)?;
                     let negated = value.negate().map_err(|error| VmError::Value {
                         error,
                         position: self.current_position(),
                     })?;
                     let register = Register::Value(negated);
 
-                    self.set_register(destination, register)?;
+                    self.set_register(a, register)?;
                 }
                 Operation::Not => {
-                    let Not {
+                    let value = self.get_argument(b, b_is_constant)?;
-                        destination,
-                        argument,
-                    } = Not::from(&instruction);
-                    let value = self.get_argument(argument)?;
                     let not = value.not().map_err(|error| VmError::Value {
                         error,
                         position: self.current_position(),
                     })?;
                     let register = Register::Value(not);
 
-                    self.set_register(destination, register)?;
+                    self.set_register(a, register)?;
                 }
                 Operation::Jump => {
-                    let Jump {
+                    self.jump(b as usize, c != 0);
-                        offset,
-                        is_positive,
-                    } = Jump::from(&instruction);
-
-                    self.jump(offset as usize, is_positive);
                 }
                 Operation::Call => {
-                    let Call {
+                    let function = self.get_argument(b, b_is_constant)?;
-                        destination,
-                        function,
-                        argument_count,
-                    } = Call::from(&instruction);
-                    let function = self.get_argument(function)?;
                     let chunk = if let ValueRef::Concrete(ConcreteValue::Function(chunk)) = function
                     {
                         chunk
@@ -491,15 +460,25 @@ impl<'a> Vm<'a> {
                         });
                     };
                     let mut function_vm = Vm::new(self.source, chunk, Some(self));
-                    let first_argument_index = destination - argument_count;
+                    let first_argument_index = a - c;
+                    let mut argument_index = 0;
+
+                    for argument_register_index in first_argument_index..a {
+                        let target_register_is_empty = matches!(
+                            self.stack[argument_register_index as usize],
+                            Register::Empty
+                        );
+
+                        if target_register_is_empty {
+                            continue;
+                        }
 
-                    for (argument_index, argument_register_index) in
-                        (first_argument_index..destination).enumerate()
-                    {
                         function_vm.set_register(
                             argument_index as u8,
                             Register::Pointer(Pointer::ParentStack(argument_register_index)),
                         )?;
+
+                        argument_index += 1;
                     }
 
                     let return_value = function_vm.run()?;
@@ -507,7 +486,7 @@ impl<'a> Vm<'a> {
                     if let Some(concrete_value) = return_value {
                         let register = Register::Value(concrete_value.to_value());
 
-                        self.set_register(destination, register)?;
+                        self.set_register(a, register)?;
                     }
                 }
                 Operation::CallNative => {
@@ -645,17 +624,15 @@ impl<'a> Vm<'a> {
 
     fn open_register(&self, register_index: u8) -> Result<ValueRef, VmError> {
         let register_index = register_index as usize;
+        let stack = self.stack.as_slice();
 
-        if register_index < self.stack.len() {
+        if register_index < stack.len() {
-            let register = &self.stack[register_index];
+            let register = &stack[register_index];
 
             return match register {
                 Register::Value(value) => Ok(value.to_ref()),
                 Register::Pointer(pointer) => self.follow_pointer(*pointer),
-                Register::Empty => Err(VmError::EmptyRegister {
+                Register::Empty => panic!("VM Error: Register {register_index} is empty"),
-                    index: register_index,
-                    position: self.current_position(),
-                }),
             };
         }
 
@@ -700,23 +677,21 @@ impl<'a> Vm<'a> {
     }
 
     /// DRY helper to get a value from an Argument
-    fn get_argument(&self, argument: Argument) -> Result<ValueRef, VmError> {
+    fn get_argument(&self, index: u8, is_constant: bool) -> Result<ValueRef, VmError> {
-        let value_ref = match argument {
+        if is_constant {
-            Argument::Constant(constant_index) => {
+            Ok(self.get_constant(index).to_value_ref())
-                ValueRef::Concrete(self.get_constant(constant_index))
+        } else {
-            }
+            Ok(self.open_register(index)?)
-            Argument::Register(register_index) => self.open_register(register_index)?,
+        }
-        };
-
-        Ok(value_ref)
     }
 
     fn set_register(&mut self, to_register: u8, register: Register) -> Result<(), VmError> {
         self.last_assigned_register = Some(to_register);
         let to_register = to_register as usize;
+        let stack = self.stack.as_mut_slice();
 
-        if to_register < self.stack.len() {
+        if to_register < stack.len() {
-            self.stack[to_register] = register;
+            stack[to_register] = register;
 
             return Ok(());
         }
@@ -899,7 +874,27 @@ impl AnnotatedError for VmError {
     }
 
     fn detail_snippets(&self) -> SmallVec<[(String, Span); 2]> {
-        todo!()
+        match self {
+            VmError::StackOverflow { position } => todo!(),
+            VmError::StackUnderflow { position } => todo!(),
+            VmError::EmptyRegister { index, position } => todo!(),
+            VmError::ExpectedConcreteValue { found, position } => todo!(),
+            VmError::ExpectedValue { found, position } => todo!(),
+            VmError::RegisterIndexOutOfBounds { index, position } => todo!(),
+            VmError::UndefinedLocal {
+                local_index,
+                position,
+            } => todo!(),
+            VmError::ExpectedBoolean { found, position } => todo!(),
+            VmError::ExpectedFunction { found, position } => todo!(),
+            VmError::ExpectedParent { position } => todo!(),
+            VmError::ValueDisplay { error, position } => todo!(),
+            VmError::ConstantIndexOutOfBounds { index, position } => todo!(),
+            VmError::InstructionIndexOutOfBounds { index, position } => todo!(),
+            VmError::LocalIndexOutOfBounds { index, position } => todo!(),
+            VmError::NativeFunction(native_function_error) => todo!(),
+            VmError::Value { error, position } => todo!(),
+        }
     }
 
     fn help_snippets(&self) -> SmallVec<[(String, Span); 2]> {