VM Tidy Up (#1610)

* - add trace to VSCode launch
- comment out pushUndefined and Return
- Move call frame to its own file
- heading for code blocks needed to be on its own line
- Show the difference between the VM starting up and a new Call frame being ran

* add back in return opCodes

* Update boa/src/vm/mod.rs

Co-authored-by: João Borges <rageknify@gmail.com>

.vscode/launch.json

@@ -28,7 +28,7 @@
           "vm"
         ]
       },
-      "args": ["${workspaceFolder}/tests/js/test.js"],
+      "args": ["-t", "${workspaceFolder}/tests/js/test.js"],
       "sourceLanguages": ["rust"]
     }
   ]

boa/src/bytecompiler.rs

@@ -868,6 +868,7 @@ impl ByteCompiler {
 
         compiler.code_block.params = paramaters.to_owned().into_boxed_slice();
 
+        // TODO These are redundant if a function returns so may need to check if a function returns and adding these if it doesn't
         compiler.emit(Opcode::PushUndefined, &[]);
         compiler.emit(Opcode::Return, &[]);
 

boa/src/vm/call_frame.rs

@@ -0,0 +1,17 @@
+//! CallFrame
+//! This module will provides everything needed to implement the CallFrame
+
+use super::CodeBlock;
+use crate::{environment::lexical_environment::Environment, JsValue};
+use gc::Gc;
+
+#[derive(Debug)]
+pub struct CallFrame {
+    pub(crate) prev: Option<Box<Self>>,
+    pub(crate) code: Gc<CodeBlock>,
+    pub(crate) pc: usize,
+    pub(crate) fp: usize,
+    pub(crate) exit_on_return: bool,
+    pub(crate) this: JsValue,
+    pub(crate) environment: Environment,
+}

boa/src/vm/code_block.rs

@@ -218,7 +218,7 @@ impl CodeBlock {
 
 impl std::fmt::Display for CodeBlock {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(
+        writeln!(
             f,
             "----------------- name '{}' (length: {}) ------------------",
             self.name, self.length

boa/src/vm/mod.rs

@@ -2,18 +2,18 @@
 //! This module will provide an instruction set for the AST to use, various traits,
 //! plus an interpreter to execute those instructions
 
-use crate::environment::lexical_environment::Environment;
 use crate::{
     builtins::Array, environment::lexical_environment::VariableScope, symbol::WellKnownSymbols,
     BoaProfiler, Context, JsResult, JsValue,
 };
 
+mod call_frame;
 mod code_block;
 mod opcode;
 
+pub use call_frame::CallFrame;
 pub use code_block::CodeBlock;
 pub use code_block::JsVmFunction;
-use gc::Gc;
 pub use opcode::Opcode;
 
 use std::{convert::TryInto, mem::size_of, time::Instant};
@@ -22,18 +22,6 @@ use self::code_block::Readable;
 
 #[cfg(test)]
 mod tests;
-
-#[derive(Debug)]
-pub struct CallFrame {
-    pub(crate) prev: Option<Box<Self>>,
-    pub(crate) code: Gc<CodeBlock>,
-    pub(crate) pc: usize,
-    pub(crate) fp: usize,
-    pub(crate) exit_on_return: bool,
-    pub(crate) this: JsValue,
-    pub(crate) environment: Environment,
-}
-
 /// Virtual Machine.
 #[derive(Debug)]
 pub struct Vm {
@@ -515,11 +503,17 @@ impl Context {
         const OPERAND_COLUMN_WIDTH: usize = COLUMN_WIDTH;
         const NUMBER_OF_COLUMNS: usize = 4;
 
+        let msg = if self.vm.frame().exit_on_return {
+            " VM Start"
+        } else {
+            " Call Frame "
+        };
+
         if self.vm.trace {
             println!("{}\n", self.vm.frame().code);
             println!(
                 "{:-^width$}",
-                " Vm Start ",
+                msg,
                 width = COLUMN_WIDTH * NUMBER_OF_COLUMNS - 10
             );
             println!(