1 //===- ListReducer.h - Trim down list while retaining property --*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This class is to be used as a base class for operations that want to zero in
11 // on a subset of the input which still causes the bug we are tracking.
13 //===----------------------------------------------------------------------===//
15 #ifndef BUGPOINT_LIST_REDUCER_H
16 #define BUGPOINT_LIST_REDUCER_H
20 template<typename ElTy>
23 NoFailure, // No failure of the predicate was detected
24 KeepSuffix, // The suffix alone satisfies the predicate
25 KeepPrefix, // The prefix alone satisfies the predicate
28 // doTest - This virtual function should be overriden by subclasses to
29 // implement the test desired. The testcase is only required to test to see
30 // if the Kept list still satisfies the property, but if it is going to check
31 // the prefix anyway, it can.
33 virtual TestResult doTest(std::vector<ElTy> &Prefix,
34 std::vector<ElTy> &Kept) = 0;
36 // reduceList - This function attempts to reduce the length of the specified
37 // list while still maintaining the "test" property. This is the core of the
38 // "work" that bugpoint does.
40 bool reduceList(std::vector<ElTy> &TheList) {
41 std::vector<ElTy> empty;
42 switch (doTest(TheList, empty)) {
44 if (TheList.size() == 1) // we are done, it's the base case and it fails
47 break; // there's definitely an error, but we need to narrow it down
51 std::cerr << "bugpoint ListReducer internal error: selected empty set.\n";
55 return false; // there is no failure with the full set of passes/funcs!
58 unsigned MidTop = TheList.size();
60 unsigned Mid = MidTop / 2;
61 std::vector<ElTy> Prefix(TheList.begin(), TheList.begin()+Mid);
62 std::vector<ElTy> Suffix(TheList.begin()+Mid, TheList.end());
64 switch (doTest(Prefix, Suffix)) {
66 // The property still holds. We can just drop the prefix elements, and
67 // shorten the list to the "kept" elements.
69 MidTop = TheList.size();
72 // The predicate still holds, shorten the list to the prefix elements.
74 MidTop = TheList.size();
77 // Otherwise the property doesn't hold. Some of the elements we removed
78 // must be necessary to maintain the property.
84 // Okay, we trimmed as much off the top and the bottom of the list as we
85 // could. If there is more two elements in the list, try deleting interior
86 // elements and testing that.
88 if (TheList.size() > 2) {
90 std::vector<ElTy> EmptyList;
93 std::vector<ElTy> TrimmedList;
94 for (unsigned i = 1; i < TheList.size()-1; ++i) { // Check interior elts
95 std::vector<ElTy> TestList(TheList);
96 TestList.erase(TestList.begin()+i);
98 if (doTest(EmptyList, TestList) == KeepSuffix) {
99 // We can trim down the list!
100 TheList.swap(TestList);
101 --i; // Don't skip an element of the list
108 return true; // there are some failure and we've narrowed them down