_shrink() — react Function Reference

Source Code

compiler/packages/babel-plugin-react-compiler/src/HIR/HIRBuilder.ts lines 618–667

function _shrink(func: HIR): void {
  const gotos = new Map();
  /*
   * Given a target block for some terminator, resolves the ideal block that should be
   * targeted instead. This transitively resolves any blocks that are simple indirections
   * (empty blocks that terminate in a goto).
   */
  function resolveBlockTarget(blockId: BlockId): BlockId {
    let target = gotos.get(blockId) ?? null;
    if (target !== null) {
      return target;
    }
    const block = func.blocks.get(blockId);
    CompilerError.invariant(block != null, {
      reason: `expected block ${blockId} to exist`,
      loc: GeneratedSource,
    });
    target = getTargetIfIndirection(block);
    if (target !== null) {
      //  the target might also be a simple goto, recurse
      target = resolveBlockTarget(target) ?? target;
      gotos.set(blockId, target);
      return target;
    } else {
      //  If the block wasn't an indirection, return the original input.
      return blockId;
    }
  }

  const queue = [func.entry];
  const reachable = new Set<BlockId>();
  while (queue.length !== 0) {
    const blockId = queue.shift()!;
    if (reachable.has(blockId)) {
      continue;
    }
    reachable.add(blockId);
    const block = func.blocks.get(blockId)!;
    block.terminal = mapTerminalSuccessors(block.terminal, prevTarget => {
      const target = resolveBlockTarget(prevTarget);
      queue.push(target);
      return target;
    });
  }
  for (const [blockId] of func.blocks) {
    if (!reachable.has(blockId)) {
      func.blocks.delete(blockId);
    }
  }
}