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diff --git a/tools/bugpoint/ListReducer.h b/tools/bugpoint/ListReducer.h
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+//===- ListReducer.h - Trim down list while retaining property --*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This class is to be used as a base class for operations that want to zero in
+// on a subset of the input which still causes the bug we are tracking.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef BUGPOINT_LIST_REDUCER_H
+#define BUGPOINT_LIST_REDUCER_H
+
+#include <vector>
+#include <iostream>
+#include <cstdlib>
+#include <algorithm>
+
+namespace llvm {
+  
+  extern bool BugpointIsInterrupted;
+
+template<typename ElTy>
+struct ListReducer {
+  enum TestResult {
+    NoFailure,         // No failure of the predicate was detected
+    KeepSuffix,        // The suffix alone satisfies the predicate
+    KeepPrefix         // The prefix alone satisfies the predicate
+  };
+
+  virtual ~ListReducer() {}
+
+  // doTest - This virtual function should be overriden by subclasses to
+  // implement the test desired.  The testcase is only required to test to see
+  // if the Kept list still satisfies the property, but if it is going to check
+  // the prefix anyway, it can.
+  //
+  virtual TestResult doTest(std::vector<ElTy> &Prefix,
+                            std::vector<ElTy> &Kept) = 0;
+
+  // reduceList - This function attempts to reduce the length of the specified
+  // list while still maintaining the "test" property.  This is the core of the
+  // "work" that bugpoint does.
+  //
+  bool reduceList(std::vector<ElTy> &TheList) {
+    std::vector<ElTy> empty;
+    std::srand(0x6e5ea738); // Seed the random number generator
+    switch (doTest(TheList, empty)) {
+    case KeepPrefix:
+      if (TheList.size() == 1) // we are done, it's the base case and it fails
+        return true;
+      else
+        break; // there's definitely an error, but we need to narrow it down
+
+    case KeepSuffix:
+      // cannot be reached!
+      std::cerr << "bugpoint ListReducer internal error: selected empty set.\n";
+      abort();
+
+    case NoFailure:
+      return false; // there is no failure with the full set of passes/funcs!
+    }
+
+    // Maximal number of allowed splitting iterations,
+    // before the elements are randomly shuffled.
+    const unsigned MaxIterationsWithoutProgress = 3;
+    bool ShufflingEnabled = true;
+
+Backjump:
+    unsigned MidTop = TheList.size();
+    unsigned MaxIterations = MaxIterationsWithoutProgress;
+    unsigned NumOfIterationsWithoutProgress = 0;
+    while (MidTop > 1) { // Binary split reduction loop
+      // Halt if the user presses ctrl-c.
+      if (BugpointIsInterrupted) {
+        std::cerr << "\n\n*** Reduction Interrupted, cleaning up...\n\n";
+        return true;
+      }
+
+      // If the loop doesn't make satisfying progress, try shuffling.
+      // The purpose of shuffling is to avoid the heavy tails of the
+      // distribution (improving the speed of convergence).
+      if (ShufflingEnabled && 
+          NumOfIterationsWithoutProgress > MaxIterations) {
+        std::vector<ElTy> ShuffledList(TheList);
+        std::random_shuffle(ShuffledList.begin(), ShuffledList.end());
+        std::cerr << "\n\n*** Testing shuffled set...\n\n";
+        // Check that random shuffle doesn't loose the bug
+        if (doTest(ShuffledList, empty) == KeepPrefix) {
+          // If the bug is still here, use the shuffled list.
+          TheList.swap(ShuffledList);
+          MidTop = TheList.size();
+          // Must increase the shuffling treshold to avoid the small 
+          // probability of inifinite looping without making progress.
+          MaxIterations += 2;
+          std::cerr << "\n\n*** Shuffling does not hide the bug...\n\n";
+        } else {
+          ShufflingEnabled = false; // Disable shuffling further on
+          std::cerr << "\n\n*** Shuffling hides the bug...\n\n";
+        }
+        NumOfIterationsWithoutProgress = 0;
+      }
+      
+      unsigned Mid = MidTop / 2;
+      std::vector<ElTy> Prefix(TheList.begin(), TheList.begin()+Mid);
+      std::vector<ElTy> Suffix(TheList.begin()+Mid, TheList.end());
+
+      switch (doTest(Prefix, Suffix)) {
+      case KeepSuffix:
+        // The property still holds.  We can just drop the prefix elements, and
+        // shorten the list to the "kept" elements.
+        TheList.swap(Suffix);
+        MidTop = TheList.size();
+        // Reset progress treshold and progress counter
+        MaxIterations = MaxIterationsWithoutProgress;
+        NumOfIterationsWithoutProgress = 0;
+        break;
+      case KeepPrefix:
+        // The predicate still holds, shorten the list to the prefix elements.
+        TheList.swap(Prefix);
+        MidTop = TheList.size();
+        // Reset progress treshold and progress counter
+        MaxIterations = MaxIterationsWithoutProgress;
+        NumOfIterationsWithoutProgress = 0;
+        break;
+      case NoFailure:
+        // Otherwise the property doesn't hold.  Some of the elements we removed
+        // must be necessary to maintain the property.
+        MidTop = Mid;
+        NumOfIterationsWithoutProgress++;
+        break;
+      }
+    }
+
+    // Probability of backjumping from the trimming loop back to the binary
+    // split reduction loop.
+    const int BackjumpProbability = 10;
+
+    // Okay, we trimmed as much off the top and the bottom of the list as we
+    // could.  If there is more than two elements in the list, try deleting 
+    // interior elements and testing that.
+    //
+    if (TheList.size() > 2) {
+      bool Changed = true;
+      std::vector<ElTy> EmptyList;
+      while (Changed) {  // Trimming loop.
+        Changed = false;
+        
+        // If the binary split reduction loop made an unfortunate sequence of
+        // splits, the trimming loop might be left off with a huge number of
+        // remaining elements (large search space). Backjumping out of that
+        // search space and attempting a different split can significantly 
+        // improve the convergence speed.
+        if (std::rand() % 100 < BackjumpProbability)
+          goto Backjump;
+        
+        for (unsigned i = 1; i < TheList.size()-1; ++i) { // Check interior elts
+          if (BugpointIsInterrupted) {
+            std::cerr << "\n\n*** Reduction Interrupted, cleaning up...\n\n";
+            return true;
+          }
+          
+          std::vector<ElTy> TestList(TheList);
+          TestList.erase(TestList.begin()+i);
+
+          if (doTest(EmptyList, TestList) == KeepSuffix) {
+            // We can trim down the list!
+            TheList.swap(TestList);
+            --i;  // Don't skip an element of the list
+            Changed = true;
+          }
+        }
+        // This can take a long time if left uncontrolled.  For now, don't
+        // iterate.
+        break;
+      }
+    }
+
+    return true; // there are some failure and we've narrowed them down
+  }
+};
+
+} // End llvm namespace
+
+#endif