是什么特殊情况的foreach循环，消除边界检查？ [英] What is the special case with the foreach loop that eliminates bounds checking?

问题描述

什么是特例在foreach /循环，消除边界检查？同时它的边界检查是什么呢？

What is the special case with the foreach/for loop that eliminates bounds checking? Also which bounds checking is it?

推荐答案

标准

for(int i = 0; i < array.Length; i++) {
    ...
}

循环是一个允许JIT以安全移除数组的边界检查（该指数是否在[0..length-1]）

loop is the one that allows the JIT to safely remove array bounds checks (whether the index is within [0..length-1])

在的foreach 遍历数组等同于标准为遍历数组。

The foreach loop over arrays is equivalent to that standard for loop over arrays.

编辑： 正如罗伯特·杰普逊所指出的：

As Robert Jeppesen points out:

如果阵列是这将被优化   本地。如果数组是访问   其他位置，边界检查会   仍然进行。参考：<一href="http://blogs.msdn.com/b/clr$c$cgeneration/archive/2009/08/13/array-bounds-check-elimination-in-the-clr.aspx"相对=nofollow称号=MSDN博客＆GT; JIT，NGEN，和c代的东西＆GT等管理$ C $;数组边界检查消除在CLR>数组边界检查消除在CLR

This will be optimized if the array is local. If the array is accessible from other locations, bounds checking will still be performed. Reference: Array Bounds Check Elimination in the CLR

谢谢！不知道我自己。

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