Context Class — react Architecture

Source Code

compiler/packages/babel-plugin-react-compiler/src/ReactiveScopes/BuildReactiveFunction.ts lines 1247–1473

class Context {
  ir: HIR;
  #nextScheduleId: number = 0;

  /*
   * Used to track which blocks *have been* generated already in order to
   * abort if a block is generated a second time. This is an error catching
   * mechanism for debugging purposes, and is not used by the codegen algorithm
   * to drive decisions about how to emit blocks.
   */
  emitted: Set<BlockId> = new Set();

  scopeFallthroughs: Set<BlockId> = new Set();
  /*
   * A set of blocks that are already scheduled to be emitted by eg a parent.
   * This allows child nodes to avoid re-emitting the same block and emit eg
   * a break instead.
   */
  #scheduled: Set<BlockId> = new Set();

  #catchHandlers: Set<BlockId> = new Set();

  /*
   * Represents which control flow operations are currently in scope, with the innermost
   * scope last. Roughly speaking, the last ControlFlowTarget on the stack indicates where
   * control will implicitly transfer, such that gotos to that block can be elided. Gotos
   * targeting items higher up the stack may need labeled break or continue; see
   * getBreakTarget() and getContinueTarget() for more details.
   */
  #controlFlowStack: Array<ControlFlowTarget> = [];

  constructor(ir: HIR) {
    this.ir = ir;
  }

  block(id: BlockId): BasicBlock {
    return this.ir.blocks.get(id)!;
  }

  scheduleCatchHandler(block: BlockId): void {
    this.#catchHandlers.add(block);
  }

  reachable(id: BlockId): boolean {
    const block = this.ir.blocks.get(id)!;
    return block.terminal.kind !== 'unreachable';
  }

  /*
   * Record that the given block will be emitted (eg by the codegen of a parent node)
   * so that child nodes can avoid re-emitting it.
   */
  schedule(block: BlockId, type: 'if' | 'switch' | 'case'): number {
    const id = this.#nextScheduleId++;
    CompilerError.invariant(!this.#scheduled.has(block), {
      reason: `Break block is already scheduled: bb${block}`,
      loc: GeneratedSource,
    });
    this.#scheduled.add(block);
    this.#controlFlowStack.push({block, id, type});
    return id;
  }

  scheduleLoop(
    fallthroughBlock: BlockId,
    continueBlock: BlockId,
    loopBlock: BlockId | null,
  ): number {
    const id = this.#nextScheduleId++;
    const ownsBlock = !this.#scheduled.has(fallthroughBlock);
    this.#scheduled.add(fallthroughBlock);
    CompilerError.invariant(!this.#scheduled.has(continueBlock), {
      reason: `Continue block is already scheduled: bb${continueBlock}`,
      loc: GeneratedSource,
    });
    this.#scheduled.add(continueBlock);
    let ownsLoop = false;
    if (loopBlock !== null) {
      ownsLoop = !this.#scheduled.has(loopBlock);
      this.#scheduled.add(loopBlock);
    }