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llvm-mirror/lib/Support/DeltaAlgorithm.cpp
Chandler Carruth ae65e281f3 Update the file headers across all of the LLVM projects in the monorepo
to reflect the new license.

We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.

Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.

llvm-svn: 351636
2019-01-19 08:50:56 +00:00

115 lines
3.4 KiB
C++

//===--- DeltaAlgorithm.cpp - A Set Minimization Algorithm -----*- C++ -*--===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//===----------------------------------------------------------------------===//
#include "llvm/ADT/DeltaAlgorithm.h"
#include <algorithm>
#include <iterator>
#include <set>
using namespace llvm;
DeltaAlgorithm::~DeltaAlgorithm() {
}
bool DeltaAlgorithm::GetTestResult(const changeset_ty &Changes) {
if (FailedTestsCache.count(Changes))
return false;
bool Result = ExecuteOneTest(Changes);
if (!Result)
FailedTestsCache.insert(Changes);
return Result;
}
void DeltaAlgorithm::Split(const changeset_ty &S, changesetlist_ty &Res) {
// FIXME: Allow clients to provide heuristics for improved splitting.
// FIXME: This is really slow.
changeset_ty LHS, RHS;
unsigned idx = 0, N = S.size() / 2;
for (changeset_ty::const_iterator it = S.begin(),
ie = S.end(); it != ie; ++it, ++idx)
((idx < N) ? LHS : RHS).insert(*it);
if (!LHS.empty())
Res.push_back(LHS);
if (!RHS.empty())
Res.push_back(RHS);
}
DeltaAlgorithm::changeset_ty
DeltaAlgorithm::Delta(const changeset_ty &Changes,
const changesetlist_ty &Sets) {
// Invariant: union(Res) == Changes
UpdatedSearchState(Changes, Sets);
// If there is nothing left we can remove, we are done.
if (Sets.size() <= 1)
return Changes;
// Look for a passing subset.
changeset_ty Res;
if (Search(Changes, Sets, Res))
return Res;
// Otherwise, partition the sets if possible; if not we are done.
changesetlist_ty SplitSets;
for (changesetlist_ty::const_iterator it = Sets.begin(),
ie = Sets.end(); it != ie; ++it)
Split(*it, SplitSets);
if (SplitSets.size() == Sets.size())
return Changes;
return Delta(Changes, SplitSets);
}
bool DeltaAlgorithm::Search(const changeset_ty &Changes,
const changesetlist_ty &Sets,
changeset_ty &Res) {
// FIXME: Parallelize.
for (changesetlist_ty::const_iterator it = Sets.begin(),
ie = Sets.end(); it != ie; ++it) {
// If the test passes on this subset alone, recurse.
if (GetTestResult(*it)) {
changesetlist_ty Sets;
Split(*it, Sets);
Res = Delta(*it, Sets);
return true;
}
// Otherwise, if we have more than two sets, see if test passes on the
// complement.
if (Sets.size() > 2) {
// FIXME: This is really slow.
changeset_ty Complement;
std::set_difference(
Changes.begin(), Changes.end(), it->begin(), it->end(),
std::insert_iterator<changeset_ty>(Complement, Complement.begin()));
if (GetTestResult(Complement)) {
changesetlist_ty ComplementSets;
ComplementSets.insert(ComplementSets.end(), Sets.begin(), it);
ComplementSets.insert(ComplementSets.end(), it + 1, Sets.end());
Res = Delta(Complement, ComplementSets);
return true;
}
}
}
return false;
}
DeltaAlgorithm::changeset_ty DeltaAlgorithm::Run(const changeset_ty &Changes) {
// Check empty set first to quickly find poor test functions.
if (GetTestResult(changeset_ty()))
return changeset_ty();
// Otherwise run the real delta algorithm.
changesetlist_ty Sets;
Split(Changes, Sets);
return Delta(Changes, Sets);
}