perf: reducing ast node memory overhead (#5133)

* perf: pack booleans in bitfield

Booleans are represented by numbers and take up 4 bytes each at the time
of this commit in v8. This commit packs all the boolean fields of the
AST nodes into a single 32-bit integer which ammortizes the cost of the
boolean fields. The end result is smaller AST nodes.

* chore: use bit shifts instead of binary literals

* chore: remove context wrapper accessor from node

We now just access through `this.scope.context` directly.

* chore: cleaning up keys assignment

---------

Co-authored-by: Lukas Taegert-Atkinson <lukastaegert@users.noreply.github.com>

src/ast/keys.ts

@@ -7,9 +7,8 @@ export const keys: {
 	Program: ['body']
 };
 
-export function getAndCreateKeys(esTreeNode: GenericEsTreeNode): string[] {
-	keys[esTreeNode.type] = Object.keys(esTreeNode).filter(
+export function createKeysForNode(esTreeNode: GenericEsTreeNode): string[] {
+	return Object.keys(esTreeNode).filter(
 		key => typeof esTreeNode[key] === 'object' && key.charCodeAt(0) !== 95 /* _ */
 	);
-	return keys[esTreeNode.type];
 }

src/ast/nodes/ArrayExpression.ts

@@ -76,7 +76,7 @@ export default class ArrayExpression extends NodeBase {
 				element.deoptimizePath(UNKNOWN_PATH);
 			}
 		}
-		this.context.requestTreeshakingPass();
+		this.scope.context.requestTreeshakingPass();
 	}
 
 	private getObjectEntity(): ObjectEntity {

src/ast/nodes/ArrowFunctionExpression.ts

@@ -14,7 +14,6 @@ import { OBJECT_PROTOTYPE } from './shared/ObjectPrototype';
 import type { PatternNode } from './shared/Pattern';
 
 export default class ArrowFunctionExpression extends FunctionBase {
-	declare async: boolean;
 	declare body: BlockStatement | ExpressionNode;
 	declare params: readonly PatternNode[];
 	declare preventChildBlockScope: true;
@@ -23,7 +22,7 @@ export default class ArrowFunctionExpression extends FunctionBase {
 	protected objectEntity: ObjectEntity | null = null;
 
 	createScope(parentScope: Scope): void {
-		this.scope = new ReturnValueScope(parentScope, this.context);
+		this.scope = new ReturnValueScope(parentScope, this.scope.context);
 	}
 
 	hasEffects(): boolean {

src/ast/nodes/AssignmentExpression.ts

@@ -155,6 +155,6 @@ export default class AssignmentExpression extends NodeBase {
 		this.deoptimized = true;
 		this.left.deoptimizePath(EMPTY_PATH);
 		this.right.deoptimizePath(UNKNOWN_PATH);
-		this.context.requestTreeshakingPass();
+		this.scope.context.requestTreeshakingPass();
 	}
 }

src/ast/nodes/AssignmentPattern.ts

@@ -58,6 +58,6 @@ export default class AssignmentPattern extends NodeBase implements PatternNode {
 		this.deoptimized = true;
 		this.left.deoptimizePath(EMPTY_PATH);
 		this.right.deoptimizePath(UNKNOWN_PATH);
-		this.context.requestTreeshakingPass();
+		this.scope.context.requestTreeshakingPass();
 	}
 }

src/ast/nodes/AwaitExpression.ts

@@ -17,13 +17,13 @@ export default class AwaitExpression extends NodeBase {
 		if (!this.deoptimized) this.applyDeoptimizations();
 		if (!this.included) {
 			this.included = true;
-			checkTopLevelAwait: if (!this.context.usesTopLevelAwait) {
+			checkTopLevelAwait: if (!this.scope.context.usesTopLevelAwait) {
 				let parent = this.parent;
 				do {
 					if (parent instanceof FunctionNode || parent instanceof ArrowFunctionExpression)
 						break checkTopLevelAwait;
 				} while ((parent = (parent as Node).parent as Node));
-				this.context.usesTopLevelAwait = true;
+				this.scope.context.usesTopLevelAwait = true;
 			}
 		}
 		this.argument.include(context, includeChildrenRecursively);

src/ast/nodes/BlockStatement.ts

@@ -3,18 +3,29 @@ import { type RenderOptions, renderStatementList } from '../../utils/renderHelpe
 import type { HasEffectsContext, InclusionContext } from '../ExecutionContext';
 import BlockScope from '../scopes/BlockScope';
 import type ChildScope from '../scopes/ChildScope';
-import type Scope from '../scopes/Scope';
 import ExpressionStatement from './ExpressionStatement';
 import * as NodeType from './NodeType';
+import { Flag, isFlagSet, setFlag } from './shared/BitFlags';
 import { UNKNOWN_EXPRESSION } from './shared/Expression';
 import { type IncludeChildren, type Node, StatementBase, type StatementNode } from './shared/Node';
 
 export default class BlockStatement extends StatementBase {
 	declare body: readonly StatementNode[];
 	declare type: NodeType.tBlockStatement;
 
-	private declare deoptimizeBody: boolean;
-	private directlyIncluded = false;
+	private get deoptimizeBody(): boolean {
+		return isFlagSet(this.flags, Flag.deoptimizeBody);
+	}
+	private set deoptimizeBody(value: boolean) {
+		this.flags = setFlag(this.flags, Flag.deoptimizeBody, value);
+	}
+
+	private get directlyIncluded(): boolean {
+		return isFlagSet(this.flags, Flag.directlyIncluded);
+	}
+	private set directlyIncluded(value: boolean) {
+		this.flags = setFlag(this.flags, Flag.directlyIncluded, value);
+	}
 
 	addImplicitReturnExpressionToScope(): void {
 		const lastStatement = this.body[this.body.length - 1];
@@ -23,10 +34,10 @@ export default class BlockStatement extends StatementBase {
 		}
 	}
 
-	createScope(parentScope: Scope): void {
+	createScope(parentScope: ChildScope): void {
 		this.scope = (this.parent as Node).preventChildBlockScope
 			? (parentScope as ChildScope)
-			: new BlockScope(parentScope);
+			: new BlockScope(parentScope, this.scope.context);
 	}
 
 	hasEffects(context: HasEffectsContext): boolean {

src/ast/nodes/CallExpression.ts

@@ -13,6 +13,7 @@ import MemberExpression from './MemberExpression';
 import type * as NodeType from './NodeType';
 import type SpreadElement from './SpreadElement';
 import type Super from './Super';
+import { Flag, isFlagSet, setFlag } from './shared/BitFlags';
 import CallExpressionBase from './shared/CallExpressionBase';
 import { type ExpressionEntity, UNKNOWN_RETURN_EXPRESSION } from './shared/Expression';
 import type { ChainElement, ExpressionNode, IncludeChildren } from './shared/Node';
@@ -24,20 +25,26 @@ export default class CallExpression
 {
 	declare arguments: (ExpressionNode | SpreadElement)[];
 	declare callee: ExpressionNode | Super;
-	declare optional: boolean;
 	declare type: NodeType.tCallExpression;
 
+	get optional(): boolean {
+		return isFlagSet(this.flags, Flag.optional);
+	}
+	set optional(value: boolean) {
+		this.flags = setFlag(this.flags, Flag.optional, value);
+	}
+
 	bind(): void {
 		super.bind();
 		if (this.callee instanceof Identifier) {
 			const variable = this.scope.findVariable(this.callee.name);
 
 			if (variable.isNamespace) {
-				this.context.log(LOGLEVEL_WARN, logCannotCallNamespace(this.callee.name), this.start);
+				this.scope.context.log(LOGLEVEL_WARN, logCannotCallNamespace(this.callee.name), this.start);
 			}
 
 			if (this.callee.name === 'eval') {
-				this.context.log(LOGLEVEL_WARN, logEval(this.context.module.id), this.start);
+				this.scope.context.log(LOGLEVEL_WARN, logEval(this.scope.context.module.id), this.start);
 			}
 		}
 		this.interaction = {
@@ -114,7 +121,7 @@ export default class CallExpression
 			EMPTY_PATH,
 			SHARED_RECURSION_TRACKER
 		);
-		this.context.requestTreeshakingPass();
+		this.scope.context.requestTreeshakingPass();
 	}
 
 	protected getReturnExpression(

src/ast/nodes/CatchClause.ts

@@ -1,5 +1,5 @@
 import CatchScope from '../scopes/CatchScope';
-import type Scope from '../scopes/Scope';
+import type ChildScope from '../scopes/ChildScope';
 import type BlockStatement from './BlockStatement';
 import type * as NodeType from './NodeType';
 import { UNKNOWN_EXPRESSION } from './shared/Expression';
@@ -13,8 +13,8 @@ export default class CatchClause extends NodeBase {
 	declare scope: CatchScope;
 	declare type: NodeType.tCatchClause;
 
-	createScope(parentScope: Scope): void {
-		this.scope = new CatchScope(parentScope, this.context);
+	createScope(parentScope: ChildScope): void {
+		this.scope = new CatchScope(parentScope, this.scope.context);
 	}
 
 	parseNode(esTreeNode: GenericEsTreeNode): void {
@@ -23,7 +23,7 @@ export default class CatchClause extends NodeBase {
 		// name instead of the variable
 		const { param } = esTreeNode;
 		if (param) {
-			(this.param as GenericEsTreeNode) = new (this.context.getNodeConstructor(param.type))(
+			(this.param as GenericEsTreeNode) = new (this.scope.context.getNodeConstructor(param.type))(
 				param,
 				this,
 				this.scope

src/ast/nodes/ClassBody.ts

@@ -1,6 +1,7 @@
 import type { InclusionContext } from '../ExecutionContext';
+import type ChildScope from '../scopes/ChildScope';
 import ClassBodyScope from '../scopes/ClassBodyScope';
-import type Scope from '../scopes/Scope';
+
 import type MethodDefinition from './MethodDefinition';
 import type * as NodeType from './NodeType';
 import type PropertyDefinition from './PropertyDefinition';
@@ -12,13 +13,13 @@ export default class ClassBody extends NodeBase {
 	declare scope: ClassBodyScope;
 	declare type: NodeType.tClassBody;
 
-	createScope(parentScope: Scope): void {
-		this.scope = new ClassBodyScope(parentScope, this.parent as ClassNode, this.context);
+	createScope(parentScope: ChildScope): void {
+		this.scope = new ClassBodyScope(parentScope, this.parent as ClassNode, this.scope.context);
 	}
 
 	include(context: InclusionContext, includeChildrenRecursively: IncludeChildren): void {
 		this.included = true;
-		this.context.includeVariableInModule(this.scope.thisVariable);
+		this.scope.context.includeVariableInModule(this.scope.thisVariable);
 		for (const definition of this.body) {
 			definition.include(context, includeChildrenRecursively);
 		}
@@ -28,7 +29,7 @@ export default class ClassBody extends NodeBase {
 		const body: NodeBase[] = (this.body = []);
 		for (const definition of esTreeNode.body) {
 			body.push(
-				new (this.context.getNodeConstructor(definition.type))(
+				new (this.scope.context.getNodeConstructor(definition.type))(
 					definition,
 					this,
 					definition.static ? this.scope : this.scope.instanceScope

src/ast/nodes/ConditionalExpression.ts

@@ -13,6 +13,7 @@ import type { ObjectPath, PathTracker } from '../utils/PathTracker';
 import { EMPTY_PATH, SHARED_RECURSION_TRACKER, UNKNOWN_PATH } from '../utils/PathTracker';
 import type * as NodeType from './NodeType';
 import type SpreadElement from './SpreadElement';
+import { Flag, isFlagSet, setFlag } from './shared/BitFlags';
 import type { ExpressionEntity, LiteralValueOrUnknown } from './shared/Expression';
 import { UnknownValue } from './shared/Expression';
 import { MultiExpression } from './shared/MultiExpression';
@@ -25,8 +26,14 @@ export default class ConditionalExpression extends NodeBase implements Deoptimiz
 	declare test: ExpressionNode;
 	declare type: NodeType.tConditionalExpression;
 
+	get isBranchResolutionAnalysed(): boolean {
+		return isFlagSet(this.flags, Flag.isBranchResolutionAnalysed);
+	}
+	set isBranchResolutionAnalysed(value: boolean) {
+		this.flags = setFlag(this.flags, Flag.isBranchResolutionAnalysed, value);
+	}
+
 	private expressionsToBeDeoptimized: DeoptimizableEntity[] = [];
-	private isBranchResolutionAnalysed = false;
 	private usedBranch: ExpressionNode | null = null;
 
 	deoptimizeArgumentsOnInteractionAtPath(

src/ast/nodes/ExportAllDeclaration.ts

@@ -18,7 +18,7 @@ export default class ExportAllDeclaration extends NodeBase {
 	}
 
 	initialise(): void {
-		this.context.addExport(this);
+		this.scope.context.addExport(this);
 	}
 
 	render(code: MagicString, _options: RenderOptions, nodeRenderOptions?: NodeRenderOptions): void {

src/ast/nodes/ExportDefaultDeclaration.ts

@@ -44,7 +44,7 @@ export default class ExportDefaultDeclaration extends NodeBase {
 	include(context: InclusionContext, includeChildrenRecursively: IncludeChildren): void {
 		super.include(context, includeChildrenRecursively);
 		if (includeChildrenRecursively) {
-			this.context.includeVariableInModule(this.variable);
+			this.scope.context.includeVariableInModule(this.variable);
 		}
 	}
 
@@ -53,11 +53,11 @@ export default class ExportDefaultDeclaration extends NodeBase {
 		this.declarationName =
 			(declaration.id && declaration.id.name) || (this.declaration as Identifier).name;
 		this.variable = this.scope.addExportDefaultDeclaration(
-			this.declarationName || this.context.getModuleName(),
+			this.declarationName || this.scope.context.getModuleName(),
 			this,
-			this.context
+			this.scope.context
 		);
-		this.context.addExport(this);
+		this.scope.context.addExport(this);
 	}
 
 	removeAnnotations(code: MagicString) {

src/ast/nodes/ExportNamedDeclaration.ts

@@ -28,7 +28,7 @@ export default class ExportNamedDeclaration extends NodeBase {
 	}
 
 	initialise(): void {
-		this.context.addExport(this);
+		this.scope.context.addExport(this);
 	}
 
 	removeAnnotations(code: MagicString) {

src/ast/nodes/ExpressionStatement.ts

@@ -16,10 +16,10 @@ export default class ExpressionStatement extends StatementBase {
 			this.directive !== 'use strict' &&
 			this.parent.type === NodeType.Program
 		) {
-			this.context.log(
+			this.scope.context.log(
 				LOGLEVEL_WARN,
 				// This is necessary, because either way (deleting or not) can lead to errors.
-				logModuleLevelDirective(this.directive, this.context.module.id),
+				logModuleLevelDirective(this.directive, this.scope.context.module.id),
 				this.start
 			);
 		}

src/ast/nodes/ForInStatement.ts

@@ -2,7 +2,7 @@ import type MagicString from 'magic-string';
 import { NO_SEMICOLON, type RenderOptions } from '../../utils/renderHelpers';
 import type { HasEffectsContext, InclusionContext } from '../ExecutionContext';
 import BlockScope from '../scopes/BlockScope';
-import type Scope from '../scopes/Scope';
+import type ChildScope from '../scopes/ChildScope';
 import { EMPTY_PATH } from '../utils/PathTracker';
 import type MemberExpression from './MemberExpression';
 import type * as NodeType from './NodeType';
@@ -23,8 +23,8 @@ export default class ForInStatement extends StatementBase {
 	declare right: ExpressionNode;
 	declare type: NodeType.tForInStatement;
 
-	createScope(parentScope: Scope): void {
-		this.scope = new BlockScope(parentScope);
+	createScope(parentScope: ChildScope): void {
+		this.scope = new BlockScope(parentScope, this.scope.context);
 	}
 
 	hasEffects(context: HasEffectsContext): boolean {
@@ -60,6 +60,6 @@ export default class ForInStatement extends StatementBase {
 	protected applyDeoptimizations(): void {
 		this.deoptimized = true;
 		this.left.deoptimizePath(EMPTY_PATH);
-		this.context.requestTreeshakingPass();
+		this.scope.context.requestTreeshakingPass();
 	}
 }

src/ast/nodes/ForOfStatement.ts

@@ -2,11 +2,12 @@ import type MagicString from 'magic-string';
 import { NO_SEMICOLON, type RenderOptions } from '../../utils/renderHelpers';
 import type { InclusionContext } from '../ExecutionContext';
 import BlockScope from '../scopes/BlockScope';
-import type Scope from '../scopes/Scope';
+import type ChildScope from '../scopes/ChildScope';
 import { EMPTY_PATH, UNKNOWN_PATH } from '../utils/PathTracker';
 import type MemberExpression from './MemberExpression';
 import type * as NodeType from './NodeType';
 import type VariableDeclaration from './VariableDeclaration';
+import { Flag, isFlagSet, setFlag } from './shared/BitFlags';
 import { UNKNOWN_EXPRESSION } from './shared/Expression';
 import {
 	type ExpressionNode,
@@ -18,14 +19,20 @@ import type { PatternNode } from './shared/Pattern';
 import { includeLoopBody } from './shared/loops';
 
 export default class ForOfStatement extends StatementBase {
-	declare await: boolean;
 	declare body: StatementNode;
 	declare left: VariableDeclaration | PatternNode | MemberExpression;
 	declare right: ExpressionNode;
 	declare type: NodeType.tForOfStatement;
 
-	createScope(parentScope: Scope): void {
-		this.scope = new BlockScope(parentScope);
+	get await(): boolean {
+		return isFlagSet(this.flags, Flag.await);
+	}
+	set await(value: boolean) {
+		this.flags = setFlag(this.flags, Flag.await, value);
+	}
+
+	createScope(parentScope: ChildScope): void {
+		this.scope = new BlockScope(parentScope, this.scope.context);
 	}
 
 	hasEffects(): boolean {
@@ -61,6 +68,6 @@ export default class ForOfStatement extends StatementBase {
 		this.deoptimized = true;
 		this.left.deoptimizePath(EMPTY_PATH);
 		this.right.deoptimizePath(UNKNOWN_PATH);
-		this.context.requestTreeshakingPass();
+		this.scope.context.requestTreeshakingPass();
 	}
 }

src/ast/nodes/ForStatement.ts

@@ -2,7 +2,7 @@ import type MagicString from 'magic-string';
 import { NO_SEMICOLON, type RenderOptions } from '../../utils/renderHelpers';
 import type { HasEffectsContext, InclusionContext } from '../ExecutionContext';
 import BlockScope from '../scopes/BlockScope';
-import type Scope from '../scopes/Scope';
+import type ChildScope from '../scopes/ChildScope';
 import type * as NodeType from './NodeType';
 import type VariableDeclaration from './VariableDeclaration';
 import {
@@ -20,8 +20,8 @@ export default class ForStatement extends StatementBase {
 	declare type: NodeType.tForStatement;
 	declare update: ExpressionNode | null;
 
-	createScope(parentScope: Scope): void {
-		this.scope = new BlockScope(parentScope);
+	createScope(parentScope: ChildScope): void {
+		this.scope = new BlockScope(parentScope, this.scope.context);
 	}
 
 	hasEffects(context: HasEffectsContext): boolean {