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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 "llvm/Support/raw_ostream.h"
-#include "llvm/Support/ErrorHandling.h"
-#include <vector>
-#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
- InternalError // Encountered an error trying to run 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,
- std::string &Error) = 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::string &Error) {
- std::vector<ElTy> empty;
- std::srand(0x6e5ea738); // Seed the random number generator
- switch (doTest(TheList, empty, Error)) {
- 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!
- llvm_unreachable("bugpoint ListReducer internal error: "
- "selected empty set.");
-
- case NoFailure:
- return false; // there is no failure with the full set of passes/funcs!
-
- case InternalError:
- assert(!Error.empty());
- return true;
- }
-
- // 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) {
- errs() << "\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());
- errs() << "\n\n*** Testing shuffled set...\n\n";
- // Check that random shuffle doesn't loose the bug
- if (doTest(ShuffledList, empty, Error) == 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;
- errs() << "\n\n*** Shuffling does not hide the bug...\n\n";
- } else {
- ShufflingEnabled = false; // Disable shuffling further on
- errs() << "\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, Error)) {
- 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;
- case InternalError:
- return true; // Error was set by doTest.
- }
- assert(Error.empty() && "doTest did not return InternalError for error");
- }
-
- // 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) {
- errs() << "\n\n*** Reduction Interrupted, cleaning up...\n\n";
- return true;
- }
-
- std::vector<ElTy> TestList(TheList);
- TestList.erase(TestList.begin()+i);
-
- if (doTest(EmptyList, TestList, Error) == KeepSuffix) {
- // We can trim down the list!
- TheList.swap(TestList);
- --i; // Don't skip an element of the list
- Changed = true;
- }
- if (!Error.empty())
- return 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
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