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118 lines
3.9 KiB
C++
118 lines
3.9 KiB
C++
//===- ListReducer.h - Trim down list while retaining property --*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by the LLVM research group and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This class is to be used as a base class for operations that want to zero in
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// on a subset of the input which still causes the bug we are tracking.
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//
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//===----------------------------------------------------------------------===//
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#ifndef BUGPOINT_LIST_REDUCER_H
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#define BUGPOINT_LIST_REDUCER_H
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#include <vector>
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#include <iostream>
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namespace llvm {
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template<typename ElTy>
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struct ListReducer {
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enum TestResult {
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NoFailure, // No failure of the predicate was detected
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KeepSuffix, // The suffix alone satisfies the predicate
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KeepPrefix, // The prefix alone satisfies the predicate
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};
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// doTest - This virtual function should be overriden by subclasses to
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// implement the test desired. The testcase is only required to test to see
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// if the Kept list still satisfies the property, but if it is going to check
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// the prefix anyway, it can.
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//
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virtual TestResult doTest(std::vector<ElTy> &Prefix,
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std::vector<ElTy> &Kept) = 0;
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// reduceList - This function attempts to reduce the length of the specified
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// list while still maintaining the "test" property. This is the core of the
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// "work" that bugpoint does.
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//
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bool reduceList(std::vector<ElTy> &TheList) {
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std::vector<ElTy> empty;
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switch (doTest(TheList, empty)) {
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case KeepPrefix:
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if (TheList.size() == 1) // we are done, it's the base case and it fails
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return true;
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else
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break; // there's definitely an error, but we need to narrow it down
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case KeepSuffix:
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// cannot be reached!
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std::cerr << "bugpoint ListReducer internal error: selected empty set.\n";
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abort();
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case NoFailure:
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return false; // there is no failure with the full set of passes/funcs!
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}
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unsigned MidTop = TheList.size();
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while (MidTop > 1) {
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unsigned Mid = MidTop / 2;
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std::vector<ElTy> Prefix(TheList.begin(), TheList.begin()+Mid);
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std::vector<ElTy> Suffix(TheList.begin()+Mid, TheList.end());
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switch (doTest(Prefix, Suffix)) {
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case KeepSuffix:
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// The property still holds. We can just drop the prefix elements, and
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// shorten the list to the "kept" elements.
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TheList.swap(Suffix);
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MidTop = TheList.size();
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break;
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case KeepPrefix:
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// The predicate still holds, shorten the list to the prefix elements.
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TheList.swap(Prefix);
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MidTop = TheList.size();
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break;
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case NoFailure:
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// Otherwise the property doesn't hold. Some of the elements we removed
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// must be necessary to maintain the property.
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MidTop = Mid;
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break;
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}
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}
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// Okay, we trimmed as much off the top and the bottom of the list as we
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// could. If there is more two elements in the list, try deleting interior
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// elements and testing that.
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//
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if (TheList.size() > 2) {
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bool Changed = true;
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std::vector<ElTy> EmptyList;
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while (Changed) {
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Changed = false;
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std::vector<ElTy> TrimmedList;
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for (unsigned i = 1; i < TheList.size()-1; ++i) { // Check interior elts
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std::vector<ElTy> TestList(TheList);
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TestList.erase(TestList.begin()+i);
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if (doTest(EmptyList, TestList) == KeepSuffix) {
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// We can trim down the list!
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TheList.swap(TestList);
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--i; // Don't skip an element of the list
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Changed = true;
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}
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}
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}
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}
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return true; // there are some failure and we've narrowed them down
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}
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};
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} // End llvm namespace
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#endif
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