[llvm] 093b5ac - [llvm][Uniformity] correctly use a vector as a set by uniqifying elements

[Sameer Sahasrabuddhe via llvm-commits]

Author: Sameer Sahasrabuddhe
Date: 2023-03-03T15:56:48+05:30
New Revision: 093b5ac85f064875f62775bba73dbaf8feb85798

URL: https://github.com/llvm/llvm-project/commit/093b5ac85f064875f62775bba73dbaf8feb85798
DIFF: https://github.com/llvm/llvm-project/commit/093b5ac85f064875f62775bba73dbaf8feb85798.diff

LOG: [llvm][Uniformity] correctly use a vector as a set by uniqifying elements

The search for temporal divergence needs to determine a dominance frontier
defined for a cycle. The implementation uses a temporary vector to store a set
of newly discovered successors. Failing to uniqify the elements in this vector
causes a very large regression in compile time due to an exponential number of
redundant visits.

This fixes github issue #61123

Reviewed By: foad

Differential Revision: https://reviews.llvm.org/D145216

Added: 
    

Modified: 
    llvm/include/llvm/ADT/GenericUniformityImpl.h

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/ADT/GenericUniformityImpl.h b/llvm/include/llvm/ADT/GenericUniformityImpl.h
index 4784d90cafc96..380da45437acf 100644
--- a/llvm/include/llvm/ADT/GenericUniformityImpl.h
+++ b/llvm/include/llvm/ADT/GenericUniformityImpl.h
@@ -876,6 +876,11 @@ void GenericUniformityAnalysisImpl<ContextT>::analyzeCycleExitDivergence(
     }
     if (!Promoted)
       break;
+
+    // Restore the set property for the temporary vector
+    llvm::sort(Temp);
+    Temp.erase(std::unique(Temp.begin(), Temp.end()), Temp.end());
+
     DomFrontier = Temp;
   }