[llvm] r326077 - [LoopInterchange] Loops with empty dependency matrix are safe.

[Philip Reames via llvm-commits]

Test case?


On 02/26/2018 02:45 AM, Florian Hahn via llvm-commits wrote:
> Author: fhahn
> Date: Mon Feb 26 02:45:25 2018
> New Revision: 326077
>
> URL: http://llvm.org/viewvc/llvm-project?rev=326077&view=rev
> Log:
> [LoopInterchange] Loops with empty dependency matrix are safe.
>
> The dependency matrix is only empty if no conflicting load/store
> instructions have been found. In that case, it is safe to interchange.
>
> For the LLVM test-suite, after this change around 1900 loops are
> interchanged, whereas it is 15 before this change. On cortex-a57,
> this gives an improvement of -0.57% on the geomean execution
> time of SPEC2006, SPEC2000 and the test-suite. There are a
> few small perf regressions, but I think we can improve on those
> by making the cost model better.
>
> Reviewers: karthikthecool, mcrosier
>
> Reviewed by: karthikthecool
>
> Differential Revision: https://reviews.llvm.org/D43236
>
> Modified:
>      llvm/trunk/lib/Transforms/Scalar/LoopInterchange.cpp
>
> Modified: llvm/trunk/lib/Transforms/Scalar/LoopInterchange.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopInterchange.cpp?rev=326077&r1=326076&r2=326077&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Scalar/LoopInterchange.cpp (original)
> +++ llvm/trunk/lib/Transforms/Scalar/LoopInterchange.cpp Mon Feb 26 02:45:25 2018
> @@ -173,9 +173,6 @@ static bool populateDependencyMatrix(Cha
>       }
>     }
>   
> -  // We don't have a DepMatrix to check legality return false.
> -  if (DepMatrix.empty())
> -    return false;
>     return true;
>   }
>   
>
>
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