为x + = 1比X = X + 1更有效？ [英] Is x += 1 more efficient than x = x + 1?

问题描述

在 X = X + 1 是 X 两次评估？如果是这样，在平均值x + = 1 ， X 只计算一次？如何在两个前pressions在编译器中间code进行评价？

In x = x + 1, is x evaluated twice? If so, does that mean in x += 1, x is only evaluated once? How are the two expressions evaluated in terms of compiler intermediate code?

例如， X ++ 可能意味着：以的位置x ，加载<$ C $的内容C> X 到寄存器，并在内存中增加x 的值。

For example, x++ could mean : take the location of x, load the contents of x into a register, and increment the value of x in memory.

此外，我已经读了 X + = 1 是有用的，当 X 不是一个简单的变量，而是一个前pression涉及的阵列。任何想法，为什么出现这种情况？

Also I have read that x += 1 is useful when x is not a simple variable, but an expression involving an array. Any ideas why this is the case?

推荐答案

在大多数编译器这些将是相同的。

In most compilers these would be identical

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