Of course, you can run loops backward instead of forward, or increment the loop counter by something other than 1, or even eliminate the loop counter completely as you do in a while statement.

当然，也可以反向而不是正向运行循环，或者使用1之外的循环计数器增量，甚至像while语句那样完全取消循环计数器。

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The outer loop decrements a loop counter variable each time through the loop.

每循环一次，外部循环都使循环计数器变量递减一次。

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More importantly, -O3 also avoids keeping the loop counter in memory, even with the original source.

更重要的是， -O3 也避免了在内存中保留循环计数器，即使使用原始源。

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