refactor(semantic): move AstNode::cfg_id to struct of arrays in AstNodes

part of #13646

Reduces AstNode from 32 to 24 bytes in the linter pipeline.

Author: Boshen

crates/oxc_linter/src/rules/eslint/getter_return.rs

@@ -234,72 +234,73 @@ impl GetterReturn {
                     break 'returns true;
                 }
             }
-            let output = set_depth_first_search(graph, Some(node.cfg_id()), |event| {
-                match event {
-                    // We only need to check paths that are normal or jump.
-                    DfsEvent::TreeEdge(a, b) => {
-                        let edges = graph.edges_connecting(a, b).collect::<Vec<_>>();
-                        if edges.iter().any(|e| {
-                            matches!(
-                                e.weight(),
-                                EdgeType::Normal
-                                    | EdgeType::Jump
-                                    | EdgeType::Error(ErrorEdgeKind::Explicit)
-                            )
-                        }) {
-                            Control::Continue
-                        } else {
-                            Control::Prune
+            let output =
+                set_depth_first_search(graph, Some(ctx.nodes().cfg_id(node.id())), |event| {
+                    match event {
+                        // We only need to check paths that are normal or jump.
+                        DfsEvent::TreeEdge(a, b) => {
+                            let edges = graph.edges_connecting(a, b).collect::<Vec<_>>();
+                            if edges.iter().any(|e| {
+                                matches!(
+                                    e.weight(),
+                                    EdgeType::Normal
+                                        | EdgeType::Jump
+                                        | EdgeType::Error(ErrorEdgeKind::Explicit)
+                                )
+                            }) {
+                                Control::Continue
+                            } else {
+                                Control::Prune
+                            }
                         }
-                    }
-                    DfsEvent::Discover(basic_block_id, _) => {
-                        let return_instruction =
-                            cfg.basic_block(basic_block_id).instructions().iter().find(|it| {
-                                match it.kind {
-                                    // Throws are classified as returning.
-                                    InstructionKind::Return(_) | InstructionKind::Throw => true,
-
-                                    // Ignore irrelevant elements.
-                                    InstructionKind::ImplicitReturn
-                                    | InstructionKind::Break(_)
-                                    | InstructionKind::Continue(_)
-                                    | InstructionKind::Iteration(_)
-                                    | InstructionKind::Unreachable
-                                    | InstructionKind::Condition
-                                    | InstructionKind::Statement => false,
-                                }
+                        DfsEvent::Discover(basic_block_id, _) => {
+                            let return_instruction =
+                                cfg.basic_block(basic_block_id).instructions().iter().find(|it| {
+                                    match it.kind {
+                                        // Throws are classified as returning.
+                                        InstructionKind::Return(_) | InstructionKind::Throw => true,
+
+                                        // Ignore irrelevant elements.
+                                        InstructionKind::ImplicitReturn
+                                        | InstructionKind::Break(_)
+                                        | InstructionKind::Continue(_)
+                                        | InstructionKind::Iteration(_)
+                                        | InstructionKind::Unreachable
+                                        | InstructionKind::Condition
+                                        | InstructionKind::Statement => false,
+                                    }
+                                });
+
+                            let does_return = return_instruction.is_some_and(|ret| {
+                                !matches!( ret.kind,
+                                InstructionKind::Return(ReturnInstructionKind::ImplicitUndefined)
+                                    if !self.allow_implicit
+                                )
                             });
 
-                        let does_return = return_instruction.is_some_and(|ret| {
-                            !matches!( ret.kind,
-                            InstructionKind::Return(ReturnInstructionKind::ImplicitUndefined)
-                                if !self.allow_implicit
-                            )
-                        });
-
-                        // Return true as the second argument to signify we should
-                        // continue walking this branch, as we haven't seen anything
-                        // that will signify to us that this path of the program will
-                        // definitely return or throw.
-                        if graph.edges_directed(basic_block_id, Direction::Outgoing).any(|e| {
-                            matches!(
-                                e.weight(),
-                                EdgeType::Jump
-                                    | EdgeType::Normal
-                                    | EdgeType::Backedge
-                                    | EdgeType::Error(ErrorEdgeKind::Explicit)
-                            )
-                        }) {
-                            Control::Continue
-                        } else if does_return {
-                            Control::Prune
-                        } else {
-                            Control::Break(())
+                            // Return true as the second argument to signify we should
+                            // continue walking this branch, as we haven't seen anything
+                            // that will signify to us that this path of the program will
+                            // definitely return or throw.
+                            if graph.edges_directed(basic_block_id, Direction::Outgoing).any(|e| {
+                                matches!(
+                                    e.weight(),
+                                    EdgeType::Jump
+                                        | EdgeType::Normal
+                                        | EdgeType::Backedge
+                                        | EdgeType::Error(ErrorEdgeKind::Explicit)
+                                )
+                            }) {
+                                Control::Continue
+                            } else if does_return {
+                                Control::Prune
+                            } else {
+                                Control::Break(())
+                            }
                         }
+                        _ => Control::Continue,
                     }
-                    _ => Control::Continue,
-                }
-            });
+                });
 
             output.break_value().is_none()
         };

crates/oxc_linter/src/rules/eslint/no_fallthrough.rs

@@ -260,7 +260,7 @@ impl Rule for NoFallthrough {
         let AstKind::SwitchStatement(switch) = node.kind() else { return };
 
         let cfg = ctx.cfg();
-        let switch_id = node.cfg_id();
+        let switch_id = ctx.nodes().cfg_id(node.id());
         let graph = cfg.graph();
 
         let (cfg_ids, tests, default, exit) = get_switch_semantic_cases(ctx, node, switch);
@@ -438,7 +438,7 @@ fn get_switch_semantic_cases(
     let graph = cfg.graph();
     let has_default = switch.cases.iter().any(SwitchCase::is_default_case);
     let (mut cfg_ids, tests, exit) = graph
-        .edges_directed(node.cfg_id(), Direction::Outgoing)
+        .edges_directed(ctx.nodes().cfg_id(node.id()), Direction::Outgoing)
         .fold((Vec::new(), Vec::new(), None), |(mut cfg_ids, mut conds, exit), it| {
             let target = it.target();
             if !matches!(it.weight(), EdgeType::Normal) {

crates/oxc_linter/src/rules/eslint/no_this_before_super.rs

@@ -75,7 +75,7 @@ impl Rule for NoThisBeforeSuper {
                     }
                 }
                 AstKind::Super(_) => {
-                    let basic_block_id = node.cfg_id();
+                    let basic_block_id = ctx.nodes().cfg_id(node.id());
                     if let AstKind::CallExpression(call_expr) = ctx.nodes().parent_kind(node.id()) {
                         let has_this_or_super_in_args =
                             Self::contains_this_or_super_in_args(&call_expr.arguments);
@@ -92,7 +92,7 @@ impl Rule for NoThisBeforeSuper {
                     }
                 }
                 AstKind::ThisExpression(_) => {
-                    let basic_block_id = node.cfg_id();
+                    let basic_block_id = ctx.nodes().cfg_id(node.id());
                     if !basic_blocks_with_super_called.contains(&basic_block_id) {
                         basic_blocks_with_local_violations
                             .entry(basic_block_id)
@@ -109,7 +109,7 @@ impl Rule for NoThisBeforeSuper {
         for node in wanted_nodes {
             let output = Self::analyze(
                 cfg,
-                node.cfg_id(),
+                ctx.nodes().cfg_id(node.id()),
                 &basic_blocks_with_super_called,
                 &basic_blocks_with_local_violations,
                 false,

crates/oxc_linter/src/rules/eslint/no_unreachable.rs

@@ -68,12 +68,13 @@ impl Rule for NoUnreachable {
         let mut infinite_loops = Vec::new();
 
         // Set the root as reachable.
-        unreachables[root.cfg_id().index()] = false;
+        let root_cfg_id = ctx.nodes().cfg_id(root.id());
+        unreachables[root_cfg_id.index()] = false;
 
         // In our first path we first check if each block is definitely unreachable, If it is then
         // we set it as such, If we encounter an infinite loop we keep its end block since it can
         // prevent other reachable blocks from ever getting executed.
-        let _: Control<()> = depth_first_search(graph, Some(root.cfg_id()), |event| {
+        let _: Control<()> = depth_first_search(graph, Some(root_cfg_id), |event| {
             if let DfsEvent::Finish(node, _) = event {
                 let unreachable = cfg.basic_block(node).is_unreachable();
                 unreachables[node.index()] = unreachable;
@@ -168,7 +169,7 @@ impl Rule for NoUnreachable {
                 continue;
             }
 
-            if unreachables[node.cfg_id().index()] {
+            if unreachables[ctx.nodes().cfg_id(node.id()).index()] {
                 ctx.diagnostic(no_unreachable_diagnostic(node.kind().span()));
             }
         }

crates/oxc_linter/src/rules/promise/always_return.rs

@@ -332,7 +332,7 @@ fn is_nodejs_terminal_statement(node: &AstNode) -> bool {
 fn has_no_return_code_path(node: &AstNode, ctx: &LintContext) -> bool {
     let cfg = ctx.cfg();
     let graph = cfg.graph();
-    let output = set_depth_first_search(graph, Some(node.cfg_id()), |event| {
+    let output = set_depth_first_search(graph, Some(ctx.nodes().cfg_id(node.id())), |event| {
         match event {
             // We only need to check paths that are normal or jump.
             DfsEvent::TreeEdge(a, b) => {

crates/oxc_linter/src/rules/react/require_render_return.rs

@@ -116,7 +116,7 @@ fn contains_return_statement(node: &AstNode, ctx: &LintContext) -> bool {
     let cfg = ctx.cfg();
     let state = neighbors_filtered_by_edge_weight(
         cfg.graph(),
-        node.cfg_id(),
+        ctx.nodes().cfg_id(node.id()),
         &|edge| match edge {
             // We only care about normal edges having a return statement.
             EdgeType::Jump | EdgeType::Normal => None,

crates/oxc_linter/src/rules/react/rules_of_hooks.rs

@@ -275,8 +275,8 @@ impl Rule for RulesOfHooks {
             return;
         }
 
-        let node_cfg_id = node.cfg_id();
-        let func_cfg_id = parent_func.cfg_id();
+        let node_cfg_id = ctx.nodes().cfg_id(node.id());
+        let func_cfg_id = ctx.nodes().cfg_id(parent_func.id());
 
         // there is no branch between us and our parent function
         if node_cfg_id == func_cfg_id {
@@ -296,20 +296,21 @@ impl Rule for RulesOfHooks {
             return ctx.diagnostic(diagnostics::loop_hook(span, hook_name));
         }
 
-        if has_conditional_path_accept_throw(cfg, parent_func, node) {
+        if has_conditional_path_accept_throw(ctx.nodes(), cfg, parent_func, node) {
             #[expect(clippy::needless_return)]
             return ctx.diagnostic(diagnostics::conditional_hook(span, hook_name));
         }
     }
 }
 
 fn has_conditional_path_accept_throw(
+    nodes: &AstNodes<'_>,
     cfg: &ControlFlowGraph,
     from: &AstNode<'_>,
     to: &AstNode<'_>,
 ) -> bool {
-    let from_graph_id = from.cfg_id();
-    let to_graph_id = to.cfg_id();
+    let from_graph_id = nodes.cfg_id(from.id());
+    let to_graph_id = nodes.cfg_id(to.id());
     let graph = cfg.graph();
     if graph
         .edges(to_graph_id)

crates/oxc_semantic/examples/cfg.rs

@@ -96,7 +96,7 @@ fn main() -> std::io::Result<()> {
 
     let mut ast_nodes_by_block = FxHashMap::<_, Vec<_>>::default();
     for node in semantic.semantic.nodes() {
-        let block = node.cfg_id();
+        let block = semantic.semantic.nodes().cfg_id(node.id());
         let block_ix = cfg.graph.node_weight(block).unwrap();
         ast_nodes_by_block.entry(*block_ix).or_default().push(node);
     }

crates/oxc_semantic/src/node.rs

@@ -22,10 +22,6 @@ pub struct AstNode<'a> {
 
     /// Associated Scope (initialized by binding)
     scope_id: ScopeId,
-
-    /// Associated `BasicBlockId` in CFG (initialized by control_flow)
-    #[cfg(feature = "cfg")]
-    cfg_id: BlockNodeId,
 }
 
 impl<'a> AstNode<'a> {
@@ -34,10 +30,10 @@ impl<'a> AstNode<'a> {
     pub(crate) fn new(
         kind: AstKind<'a>,
         scope_id: ScopeId,
-        cfg_id: BlockNodeId,
+        _cfg_id: BlockNodeId,
         id: NodeId,
     ) -> Self {
-        Self { id, kind, scope_id, cfg_id }
+        Self { id, kind, scope_id }
     }
 
     #[cfg(not(feature = "cfg"))]
@@ -51,15 +47,6 @@ impl<'a> AstNode<'a> {
         self.id
     }
 
-    /// ID of the control flow graph node this node is in.
-    ///
-    /// See [oxc_cfg::ControlFlowGraph] for more information.
-    #[inline]
-    #[cfg(feature = "cfg")]
-    pub fn cfg_id(&self) -> BlockNodeId {
-        self.cfg_id
-    }
-
     /// Access the underlying struct from [`oxc_ast`].
     #[inline]
     pub fn kind(&self) -> AstKind<'a> {
@@ -99,6 +86,9 @@ pub struct AstNodes<'a> {
     parent_ids: IndexVec<NodeId, NodeId>,
     /// `node` -> `flags`
     flags: IndexVec<NodeId, NodeFlags>,
+    /// `node` -> `cfg_id` (control flow graph node)
+    #[cfg(feature = "cfg")]
+    cfg_ids: IndexVec<NodeId, BlockNodeId>,
     /// Stores a set of bits of a fixed size, where each bit represents a single [`AstKind`]. If the bit is set (1),
     /// then the AST contains at least one node of that kind. If the bit is not set (0), then the AST does not contain
     /// any nodes of that kind.
@@ -197,6 +187,15 @@ impl<'a> AstNodes<'a> {
         &mut self.flags[node_id]
     }
 
+    /// ID of the control flow graph node this node is in.
+    ///
+    /// See [oxc_cfg::ControlFlowGraph] for more information.
+    #[inline]
+    #[cfg(feature = "cfg")]
+    pub fn cfg_id(&self, node_id: NodeId) -> BlockNodeId {
+        self.cfg_ids[node_id]
+    }
+
     /// Get the [`Program`] that's also the root of the AST.
     #[inline]
     pub fn program(&self) -> &'a Program<'a> {
@@ -228,6 +227,7 @@ impl<'a> AstNodes<'a> {
         let node = AstNode::new(kind, scope_id, cfg_id, node_id);
         self.nodes.push(node);
         self.flags.push(flags);
+        self.cfg_ids.push(cfg_id);
         self.node_kinds_set.set(kind.ty());
         node_id
     }
@@ -271,6 +271,7 @@ impl<'a> AstNodes<'a> {
         self.parent_ids.push(NodeId::ROOT);
         self.nodes.push(AstNode::new(kind, scope_id, cfg_id, NodeId::ROOT));
         self.flags.push(flags);
+        self.cfg_ids.push(cfg_id);
         self.node_kinds_set.set(AstType::Program);
         NodeId::ROOT
     }
@@ -300,6 +301,8 @@ impl<'a> AstNodes<'a> {
         self.nodes.reserve(additional);
         self.parent_ids.reserve(additional);
         self.flags.reserve(additional);
+        #[cfg(feature = "cfg")]
+        self.cfg_ids.reserve(additional);
     }
 
     /// Checks if the AST contains any nodes of the given types.