facebookarchive/prepack

Prepack emits if-statements with no consequent or alternate code

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#2,220 创建于 2018年7月6日

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 (3 评论) (0 反应) (0 负责人)JavaScript (14,268 star) (520 fork)batch import
Instant Renderenhancementhelp wantedlevel 1 (super easy)priority: lowserializer

描述

This

(function () {
  let n = global.__abstract ? __abstract("number", "23") : 23;
  if (n === 42) {
    let d = Date.now(); // dead pure generator entry
  }
})();

prepacks to

if (23 === 42) {}

which is obviously suboptimal.

During its fixpoint computation, the visitor should not visit the condition until at least one generator entry cannot be omitted.

贡献者指南

技术栈
javascript
领域
performance
议题类型
bug
难度面向新贡献者的预计实现难度，1 表示很小改动，5 表示专家级工作。
3
预计时间有经验贡献者完成调查、实现、测试并准备 pull request 的粗略时间范围。
1-3 hours
活动状态议题当前的可参与程度：新鲜、活跃、陈旧、阻塞或等待维护者输入。
stale
清晰度议题是否清楚说明期望改动、验收标准和下一步。
clear
前置要求
JavaScript knowledgeCompiler architecture basics
新手友好度1-100 的估计分数，表示该议题对首次贡献者的友好程度。
40
研究方向
Investigate the fixpoint computation and visitor code in Prepack. Look for the relevant visitor logic that handles if statements and generator entries. Determine how to delay visiting the condition until at least one generator entry is confirmed not omitted. The issue suggests a specific fix in the visitor condition traversal.