[PATCH] D74691: [Attributor] Detect possibly unbounded cycles in functions

[omar ahmed via Phabricator via llvm-commits]

omarahmed marked an inline comment as done.
omarahmed added inline comments.


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Comment at: llvm/lib/Transforms/IPO/Attributor.cpp:2398-2399
+  // then it is a bounded loop.
+  for (auto L : LI->getLoopsInPreorder()) {
+    if (!SE->getSmallConstantMaxTripCount(L))
+      return true;
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omarahmed wrote:
> baziotis wrote:
> > As I said in a previous comment, `getLoopsInPreorder()` (or any way that `LoopInfo` gives you access to all the loops) gives you the //top-level// loops. The fact that a top-level loop has a maximal trip count does not mean that its children loops (i.e. loops entirely contained within this loop) will also have a maximal trip count. So, for every top-level loop, you have to check all its children (i.e. `getSubLoops()`). And all that, in a loop / recursion, because the sub loops may themselves have children loops etc.
> I have tried it with a test like that
> 
> ```
> for(int i=0;i<n;i++)
>     for(int j =0;j<n;j++)
>         for(int k = 0;k<n;k++)
>              for(int l = 0;l<n;l++)
> ```
> and printed the loops that it iterate on and i found it had iterated even on the forth level one , also I have looked on the implementation of the cycle and found that it recursivly was going inside the loops so i guess it goes throw all of the loops not only the top-level ones or I miss something here ?
I mean the implementation of the function not cycle it is a typo :)


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https://reviews.llvm.org/D74691