我的SSA构造正确吗？ （重命名） [英] Is my construction of SSA correct? (Renaming)

问题描述

我一直在学习ssa（静态单分配形式），并且获得了以下插入了phi函数的图，但是该图尚未重命名：

I've been learning about ssa (static single assignment form), and I was given the following graph with phi functions inserted, but the graph hasn't been renamed:

< a href = https://i.stack.imgur.com/Q0jcA.png rel = nofollow noreferrer>

我不得不重命名变量，这就是我得到的：

I had to rename the variables, and this is what I got:

我非常不确定这是正确的。我是否正确重命名了变量？这是最小的ssa吗？我正在此处（Cytron等人的论文）来重命名变量。请帮忙！ ：）

I am very unsure that this is correct. Did I rename the variables correctly? Is this minimal ssa? I am using this algorithm from here (Cytron, et. al's paper) to rename the variables. Please help! :)

推荐答案

不，您的图形不正确。 x 和 y 的phi函数和重命名是正确的，问题是临时变量 t1 到 t3 。当输入块 L1 时，这些变量将失效，并且根本不需要任何phi函数。如果您坚持要这些变量使用phi函数，则必须假定变量存在，并且在输入图形时具有som不确定的值。令 t1_0 ， t2_0 和 t3_0 为这些值并更新重命名的图形相应。

No, your graph is not correct. The phi-functions and renaming for x and y are correct, the problem is the temporary variables t1 through t3. These variable are dead when the block L1 is entered and does not require any phi-functions at all. If you insist on having phi-functions for these variables you must assume that the variables exist and have som indeterminate value when the graph is entered. Let t1_0, t2_0 and t3_0 be those values and update the renamed graph accordingly.

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