//===- ListReducer.h - Trim down list while retaining property --*- C++ -*-===//
-//
+//
// The LLVM Compiler Infrastructure
//
-// This file was developed by the LLVM research group and is distributed under
-// the University of Illinois Open Source License. See LICENSE.TXT for details.
-//
+// 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
//
//===----------------------------------------------------------------------===//
-#ifndef BUGPOINT_LIST_REDUCER_H
-#define BUGPOINT_LIST_REDUCER_H
+#ifndef LLVM_TOOLS_BUGPOINT_LISTREDUCER_H
+#define LLVM_TOOLS_BUGPOINT_LISTREDUCER_H
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/raw_ostream.h"
+#include <algorithm>
+#include <cstdlib>
#include <vector>
namespace llvm {
+
+ extern bool BugpointIsInterrupted;
template<typename ElTy>
struct ListReducer {
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) = 0;
+ 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) {
+ bool reduceList(std::vector<ElTy> &TheList, std::string &Error) {
std::vector<ElTy> empty;
- switch (doTest(TheList, 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
+ 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();
+ 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;
+
+ // Maximal number of allowed single-element trim iterations. We add a
+ // threshhold here as single-element reductions may otherwise take a
+ // very long time to complete.
+ const unsigned MaxTrimIterationsWithoutBackJump = 3;
+ bool ShufflingEnabled = true;
+
+Backjump:
unsigned MidTop = TheList.size();
- while (MidTop > 1) {
+ 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)) {
+ 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 two elements in the list, try deleting interior
- // elements and testing that.
+ // 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) {
+ unsigned TrimIterations = 0;
+ while (Changed) { // Trimming loop.
Changed = false;
- std::vector<ElTy> TrimmedList;
+
+ // 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) == KeepSuffix) {
+ 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;
}
+ if (TrimIterations >= MaxTrimIterationsWithoutBackJump)
+ break;
+ TrimIterations++;
}
}
projects / oota-llvm.git / blobdiff