Simplify/Refactor exception handling and last statement value (#3053)

Author: HalidOdat

boa_engine/src/bytecompiler/class.rs

@@ -74,6 +74,7 @@ impl ByteCompiler<'_, '_> {
             compiler.pop_compile_environment();
         }
 
+        compiler.emit_opcode(Opcode::SetReturnValue);
         compiler.emit_opcode(Opcode::Return);
 
         let code = Gc::new(compiler.finish());
@@ -269,6 +270,8 @@ impl ByteCompiler<'_, '_> {
                     }
                     field_compiler.pop_compile_environment();
                     field_compiler.pop_compile_environment();
+
+                    field_compiler.emit_opcode(Opcode::SetReturnValue);
                     field_compiler.emit_opcode(Opcode::Return);
 
                     field_compiler.code_block_flags |= CodeBlockFlags::IN_CLASS_FIELD_INITIALIZER;
@@ -301,6 +304,8 @@ impl ByteCompiler<'_, '_> {
                     }
                     field_compiler.pop_compile_environment();
                     field_compiler.pop_compile_environment();
+
+                    field_compiler.emit_opcode(Opcode::SetReturnValue);
                     field_compiler.emit_opcode(Opcode::Return);
 
                     field_compiler.code_block_flags |= CodeBlockFlags::IN_CLASS_FIELD_INITIALIZER;
@@ -343,6 +348,8 @@ impl ByteCompiler<'_, '_> {
                     }
                     field_compiler.pop_compile_environment();
                     field_compiler.pop_compile_environment();
+
+                    field_compiler.emit_opcode(Opcode::SetReturnValue);
                     field_compiler.emit_opcode(Opcode::Return);
 
                     field_compiler.code_block_flags |= CodeBlockFlags::IN_CLASS_FIELD_INITIALIZER;

boa_engine/src/bytecompiler/expression/mod.rs

@@ -98,7 +98,6 @@ impl ByteCompiler<'_, '_> {
             Expression::Conditional(op) => self.compile_conditional(op, use_expr),
             Expression::ArrayLiteral(array) => {
                 self.emit_opcode(Opcode::PushNewArray);
-                self.emit_opcode(Opcode::PopOnReturnAdd);
 
                 for element in array.as_ref() {
                     if let Some(element) = element {
@@ -114,7 +113,6 @@ impl ByteCompiler<'_, '_> {
                     }
                 }
 
-                self.emit_opcode(Opcode::PopOnReturnSub);
                 if !use_expr {
                     self.emit(Opcode::Pop, &[]);
                 }
@@ -194,6 +192,8 @@ impl ByteCompiler<'_, '_> {
                         self.emit_opcode(Opcode::Await);
                     }
                     self.close_active_iterators();
+
+                    self.emit_opcode(Opcode::SetReturnValue);
                     self.emit_opcode(Opcode::GeneratorResumeReturn);
 
                     self.patch_jump(throw_method_undefined);

boa_engine/src/bytecompiler/function.rs

@@ -157,7 +157,6 @@ impl FunctionCompiler {
             .filter(|last| **last == Opcode::Return as u8)
             .is_none()
         {
-            compiler.emit_opcode(Opcode::PushUndefined);
             compiler.emit_opcode(Opcode::Return);
         }
 

boa_engine/src/bytecompiler/jump_control.rs

@@ -32,11 +32,15 @@ bitflags! {
         const SWITCH = 0b0000_0010;
         const TRY_BLOCK = 0b0000_0100;
         const LABELLED = 0b0000_1000;
-        const IN_CATCH = 0b0001_0000;
-        const IN_FINALLY = 0b0010_0000;
-        const HAS_FINALLY = 0b0100_0000;
-        const ITERATOR_LOOP = 0b1000_0000;
-        const FOR_AWAIT_OF_LOOP = 0b1_0000_0000;
+        const IN_FINALLY = 0b0001_0000;
+        const HAS_FINALLY = 0b0010_0000;
+        const ITERATOR_LOOP = 0b0100_0000;
+        const FOR_AWAIT_OF_LOOP = 0b1000_0000;
+
+        /// Is the statement compiled with use_expr set to true.
+        ///
+        /// This bitflag is inherited if the previous [`JumpControlInfo`].
+        const USE_EXPR = 0b0001_0000_0000;
     }
 }
 
@@ -134,10 +138,6 @@ impl JumpControlInfo {
         self.flags.contains(JumpControlInfoFlags::LABELLED)
     }
 
-    pub(crate) const fn in_catch(&self) -> bool {
-        self.flags.contains(JumpControlInfoFlags::IN_CATCH)
-    }
-
     pub(crate) const fn in_finally(&self) -> bool {
         self.flags.contains(JumpControlInfoFlags::IN_FINALLY)
     }
@@ -146,6 +146,10 @@ impl JumpControlInfo {
         self.flags.contains(JumpControlInfoFlags::HAS_FINALLY)
     }
 
+    pub(crate) const fn use_expr(&self) -> bool {
+        self.flags.contains(JumpControlInfoFlags::USE_EXPR)
+    }
+
     pub(crate) const fn iterator_loop(&self) -> bool {
         self.flags.contains(JumpControlInfoFlags::ITERATOR_LOOP)
     }
@@ -168,11 +172,6 @@ impl JumpControlInfo {
         self.start_address = start_address;
     }
 
-    /// Sets the `in_catch` field of `JumpControlInfo`.
-    pub(crate) fn set_in_catch(&mut self, value: bool) {
-        self.flags.set(JumpControlInfoFlags::IN_CATCH, value);
-    }
-
     /// Set the `in_finally` field of `JumpControlInfo`.
     pub(crate) fn set_in_finally(&mut self, value: bool) {
         self.flags.set(JumpControlInfoFlags::IN_FINALLY, value);
@@ -198,9 +197,9 @@ impl ByteCompiler<'_, '_> {
     /// Pushes a generic `JumpControlInfo` onto `ByteCompiler`
     ///
     /// Default `JumpControlInfoKind` is `JumpControlInfoKind::Loop`
-    pub(crate) fn push_empty_loop_jump_control(&mut self) {
-        self.jump_info
-            .push(JumpControlInfo::default().with_loop_flag(true));
+    pub(crate) fn push_empty_loop_jump_control(&mut self, use_expr: bool) {
+        let new_info = JumpControlInfo::default().with_loop_flag(true);
+        self.push_contol_info(new_info, use_expr);
     }
 
     pub(crate) fn current_jump_control_mut(&mut self) -> Option<&mut JumpControlInfo> {
@@ -212,37 +211,43 @@ impl ByteCompiler<'_, '_> {
         info.set_start_address(start_address);
     }
 
-    pub(crate) fn set_jump_control_in_finally(&mut self, value: bool) {
-        if !self.jump_info.is_empty() {
-            let info = self
-                .jump_info
-                .last_mut()
-                .expect("must have try control label");
-            assert!(info.is_try_block());
-            info.set_in_finally(value);
+    pub(crate) fn push_contol_info(&mut self, mut info: JumpControlInfo, use_expr: bool) {
+        info.flags.set(JumpControlInfoFlags::USE_EXPR, use_expr);
+
+        if let Some(last) = self.jump_info.last() {
+            // Inherits the `JumpControlInfoFlags::USE_EXPR` flag.
+            info.flags |= last.flags & JumpControlInfoFlags::USE_EXPR;
         }
+
+        self.jump_info.push(info);
     }
 
-    pub(crate) fn set_jump_control_in_catch(&mut self, value: bool) {
-        if !self.jump_info.is_empty() {
-            let info = self
-                .jump_info
-                .last_mut()
-                .expect("must have try control label");
-            assert!(info.is_try_block());
-            info.set_in_catch(value);
+    /// Does the jump control info have the `use_expr` flag set to true.
+    ///
+    /// See [`JumpControlInfoFlags`].
+    pub(crate) fn jump_control_info_has_use_expr(&self) -> bool {
+        if let Some(last) = self.jump_info.last() {
+            return last.use_expr();
         }
+
+        false
     }
 
     // ---- Labelled Statement JumpControlInfo methods ---- //
 
     /// Pushes a `LabelledStatement`'s `JumpControlInfo` onto the `jump_info` stack.
-    pub(crate) fn push_labelled_control_info(&mut self, label: Sym, start_address: u32) {
+    pub(crate) fn push_labelled_control_info(
+        &mut self,
+        label: Sym,
+        start_address: u32,
+        use_expr: bool,
+    ) {
         let new_info = JumpControlInfo::default()
             .with_labelled_block_flag(true)
             .with_label(Some(label))
             .with_start_address(start_address);
-        self.jump_info.push(new_info);
+
+        self.push_contol_info(new_info, use_expr);
     }
 
     /// Pops and handles the info for a label's `JumpControlInfo`
@@ -267,40 +272,50 @@ impl ByteCompiler<'_, '_> {
     // ---- `IterationStatement`'s `JumpControlInfo` methods ---- //
 
     /// Pushes an `WhileStatement`, `ForStatement` or `DoWhileStatement`'s `JumpControlInfo` on to the `jump_info` stack.
-    pub(crate) fn push_loop_control_info(&mut self, label: Option<Sym>, start_address: u32) {
+    pub(crate) fn push_loop_control_info(
+        &mut self,
+        label: Option<Sym>,
+        start_address: u32,
+        use_expr: bool,
+    ) {
         let new_info = JumpControlInfo::default()
             .with_loop_flag(true)
             .with_label(label)
             .with_start_address(start_address);
-        self.jump_info.push(new_info);
+
+        self.push_contol_info(new_info, use_expr);
     }
 
     /// Pushes a `ForInOfStatement`'s `JumpControlInfo` on to the `jump_info` stack.
     pub(crate) fn push_loop_control_info_for_of_in_loop(
         &mut self,
         label: Option<Sym>,
         start_address: u32,
+        use_expr: bool,
     ) {
         let new_info = JumpControlInfo::default()
             .with_loop_flag(true)
             .with_label(label)
             .with_start_address(start_address)
             .with_iterator_loop(true);
-        self.jump_info.push(new_info);
+
+        self.push_contol_info(new_info, use_expr);
     }
 
     pub(crate) fn push_loop_control_info_for_await_of_loop(
         &mut self,
         label: Option<Sym>,
         start_address: u32,
+        use_expr: bool,
     ) {
         let new_info = JumpControlInfo::default()
             .with_loop_flag(true)
             .with_label(label)
             .with_start_address(start_address)
             .with_iterator_loop(true)
             .with_for_await_of_loop(true);
-        self.jump_info.push(new_info);
+
+        self.push_contol_info(new_info, use_expr);
     }
 
     /// Pops and handles the info for a loop control block's `JumpControlInfo`
@@ -327,12 +342,18 @@ impl ByteCompiler<'_, '_> {
     // ---- `SwitchStatement` `JumpControlInfo` methods ---- //
 
     /// Pushes a `SwitchStatement`'s `JumpControlInfo` on to the `jump_info` stack.
-    pub(crate) fn push_switch_control_info(&mut self, label: Option<Sym>, start_address: u32) {
+    pub(crate) fn push_switch_control_info(
+        &mut self,
+        label: Option<Sym>,
+        start_address: u32,
+        use_expr: bool,
+    ) {
         let new_info = JumpControlInfo::default()
             .with_switch_flag(true)
             .with_label(label)
             .with_start_address(start_address);
-        self.jump_info.push(new_info);
+
+        self.push_contol_info(new_info, use_expr);
     }
 
     /// Pops and handles the info for a switch block's `JumpControlInfo`
@@ -354,13 +375,18 @@ impl ByteCompiler<'_, '_> {
     // ---- `TryStatement`'s `JumpControlInfo` methods ---- //
 
     /// Pushes a `TryStatement`'s `JumpControlInfo` onto the `jump_info` stack.
-    pub(crate) fn push_try_control_info(&mut self, has_finally: bool, start_address: u32) {
+    pub(crate) fn push_try_control_info(
+        &mut self,
+        has_finally: bool,
+        start_address: u32,
+        use_expr: bool,
+    ) {
         let new_info = JumpControlInfo::default()
             .with_try_block_flag(true)
             .with_start_address(start_address)
             .with_has_finally(has_finally);
 
-        self.jump_info.push(new_info);
+        self.push_contol_info(new_info, use_expr);
     }
 
     /// Pops and handles the info for a try block's `JumpControlInfo`
@@ -406,12 +432,12 @@ impl ByteCompiler<'_, '_> {
     }
 
     /// Pushes a `TryStatement`'s Finally block `JumpControlInfo` onto the `jump_info` stack.
-    pub(crate) fn push_init_finally_control_info(&mut self) {
+    pub(crate) fn push_init_finally_control_info(&mut self, use_expr: bool) {
         let mut new_info = JumpControlInfo::default().with_try_block_flag(true);
 
         new_info.set_in_finally(true);
 
-        self.jump_info.push(new_info);
+        self.push_contol_info(new_info, use_expr);
     }
 
     pub(crate) fn pop_finally_control_info(&mut self) {

boa_engine/src/bytecompiler/mod.rs

@@ -756,7 +756,7 @@ impl<'ctx, 'host> ByteCompiler<'ctx, 'host> {
 
     /// Compile a [`StatementList`].
     pub fn compile_statement_list(&mut self, list: &StatementList, use_expr: bool, block: bool) {
-        if use_expr {
+        if use_expr || self.jump_control_info_has_use_expr() {
             let mut has_returns_value = false;
             let mut use_expr_index = 0;
             let mut first_return_is_abrupt = false;
@@ -781,6 +781,7 @@ impl<'ctx, 'host> ByteCompiler<'ctx, 'host> {
 
             if first_return_is_abrupt {
                 self.emit_opcode(Opcode::PushUndefined);
+                self.emit_opcode(Opcode::SetReturnValue);
             }
 
             for (i, item) in list.statements().iter().enumerate() {
@@ -1055,7 +1056,7 @@ impl<'ctx, 'host> ByteCompiler<'ctx, 'host> {
     fn compile_stmt_list_item(&mut self, item: &StatementListItem, use_expr: bool, block: bool) {
         match item {
             StatementListItem::Statement(stmt) => {
-                self.compile_stmt(stmt, use_expr);
+                self.compile_stmt(stmt, use_expr, false);
             }
             StatementListItem::Declaration(decl) => self.compile_decl(decl, block),
         }

boa_engine/src/bytecompiler/statement/break.rs

@@ -7,26 +7,12 @@ use boa_interner::Sym;
 
 impl ByteCompiler<'_, '_> {
     /// Compile a [`Break`] `boa_ast` node
-    pub(crate) fn compile_break(&mut self, node: Break) {
-        let opcode = if node.label().is_some() {
-            Opcode::BreakLabel
-        } else {
-            Opcode::Break
-        };
-
+    pub(crate) fn compile_break(&mut self, node: Break, _use_expr: bool) {
         if let Some(info) = self.jump_info.last().filter(|info| info.is_try_block()) {
-            let in_finally = info.in_finally();
-            let in_catch_no_finally = info.in_catch() && !info.has_finally();
             let has_finally_or_is_finally = info.has_finally() || info.in_finally();
 
-            if in_finally {
-                self.emit_opcode(Opcode::PopIfThrown);
-            }
-            if in_finally || in_catch_no_finally {
-                self.emit_opcode(Opcode::CatchEnd2);
-            }
-
-            let (break_label, target_jump_label) = self.emit_opcode_with_two_operands(opcode);
+            let (break_label, target_jump_label) =
+                self.emit_opcode_with_two_operands(Opcode::Break);
 
             if let Some(node_label) = node.label() {
                 let info = self.jump_info_label(node_label);
@@ -54,7 +40,7 @@ impl ByteCompiler<'_, '_> {
         }
 
         // Emit the break opcode -> (Label, Label)
-        let (break_label, target_label) = self.emit_opcode_with_two_operands(opcode);
+        let (break_label, target_label) = self.emit_opcode_with_two_operands(Opcode::Break);
         if let Some(label) = node.label() {
             let info = self.jump_info_label(label);
             info.push_break_label(break_label);

boa_engine/src/bytecompiler/statement/continue.rs

@@ -3,18 +3,11 @@ use boa_ast::statement::Continue;
 
 impl ByteCompiler<'_, '_> {
     #[allow(clippy::unnecessary_wraps)]
-    pub(crate) fn compile_continue(&mut self, node: Continue) {
+    pub(crate) fn compile_continue(&mut self, node: Continue, _use_expr: bool) {
         if let Some(info) = self.jump_info.last().filter(|info| info.is_try_block()) {
             let in_finally = info.in_finally();
             let in_finally_or_has_finally = in_finally || info.has_finally();
-            let in_catch_no_finally = !info.has_finally() && info.in_catch();
 
-            if in_finally {
-                self.emit_opcode(Opcode::PopIfThrown);
-            }
-            if in_finally || in_catch_no_finally {
-                self.emit_opcode(Opcode::CatchEnd2);
-            }
             // 1. Handle if node has a label.
             if let Some(node_label) = node.label() {
                 let items = self.jump_info.iter().rev().filter(|info| info.is_loop());