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 //===----------------------------------------------------------------------===//
11 // This class is to be used as a base class for operations that want to zero in
12 // on a subset of the input which still causes the bug we are tracking.
14 //===----------------------------------------------------------------------===//
16 #ifndef BUGPOINT_LIST_REDUCER_H
17 #define BUGPOINT_LIST_REDUCER_H
21 template<typename ElTy>
24 NoFailure, // No failure of the predicate was detected
25 KeepSuffix, // The suffix alone satisfies the predicate
26 KeepPrefix, // The prefix alone satisfies the predicate
29 // doTest - This virtual function should be overriden by subclasses to
30 // implement the test desired. The testcase is only required to test to see
31 // if the Kept list still satisfies the property, but if it is going to check
32 // the prefix anyway, it can.
34 virtual TestResult doTest(std::vector<ElTy> &Prefix,
35 std::vector<ElTy> &Kept) = 0;
37 // reduceList - This function attempts to reduce the length of the specified
38 // list while still maintaining the "test" property. This is the core of the
39 // "work" that bugpoint does.
41 bool reduceList(std::vector<ElTy> &TheList) {
42 std::vector<ElTy> empty;
43 switch (doTest(TheList, empty)) {
45 if (TheList.size() == 1) // we are done, it's the base case and it fails
48 break; // there's definitely an error, but we need to narrow it down
52 std::cerr << "bugpoint ListReducer internal error: selected empty set.\n";
56 return false; // there is no failure with the full set of passes/funcs!
59 unsigned MidTop = TheList.size();
61 unsigned Mid = MidTop / 2;
62 std::vector<ElTy> Prefix(TheList.begin(), TheList.begin()+Mid);
63 std::vector<ElTy> Suffix(TheList.begin()+Mid, TheList.end());
65 switch (doTest(Prefix, Suffix)) {
67 // The property still holds. We can just drop the prefix elements, and
68 // shorten the list to the "kept" elements.
70 MidTop = TheList.size();
73 // The predicate still holds, shorten the list to the prefix elements.
75 MidTop = TheList.size();
78 // Otherwise the property doesn't hold. Some of the elements we removed
79 // must be necessary to maintain the property.
85 // Okay, we trimmed as much off the top and the bottom of the list as we
86 // could. If there is more two elements in the list, try deleting interior
87 // elements and testing that.
89 if (TheList.size() > 2) {
91 std::vector<ElTy> EmptyList;
94 std::vector<ElTy> TrimmedList;
95 for (unsigned i = 1; i < TheList.size()-1; ++i) { // Check interior elts
96 std::vector<ElTy> TestList(TheList);
97 TestList.erase(TestList.begin()+i);
99 if (doTest(EmptyList, TestList) == KeepSuffix) {
100 // We can trim down the list!
101 TheList.swap(TestList);
102 --i; // Don't skip an element of the list
109 return true; // there are some failure and we've narrowed them down