[PATCH] D81036: [OpenMP] Begin Adding Analysis Remarks for OpenMP Best Practises.

[Joseph Huber via Phabricator via llvm-commits]

jhuber6 marked an inline comment as done.
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================
Comment at: llvm/lib/Transforms/IPO/OpenMPOpt.cpp:413
+    return false;
+  }
+
----------------
jdoerfert wrote:
> Early exits are usually easier to read, thus:
> ```
> if (!UV)
>  return;
> ```
> 
> ---
> 
> Maybe we should be more descriptive, telling people that fixed numbers are not future compatible. *And* we should not issue the remark if we find a worksharing loop with a constant trip count (that is a multiple of this constant). I guess the latter part can just be a TODO for now, maybe also a test case:
> ```
> #pragma omp parallel for num_threads(8)
> for (int i = 0; i < 8; ++i)
>   body(i);
> ```
> That reminds me that we should determine the loop trip count for worksharing loops as well. We could even use that value to feed it into "set_num_threads" to avoid waking more threads than needed.
Might be helpful, something like "Use of OpenMP parallel region with constant number of threads is not future compatibile. Consider a dynamic thread count instead." 

And are there any general ways to extract the loop tripcount in LLVM? Depending on where you are in the optimization the loop could take many different forms as far as I'm aware.


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  https://reviews.llvm.org/D81036/new/

https://reviews.llvm.org/D81036