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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
118 lines
4.1 KiB
C++
118 lines
4.1 KiB
C++
//===- CFGUpdate.h - Encode a CFG Edge Update. ------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines a CFG Edge Update: Insert or Delete, and two Nodes as the
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// Edge ends.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_SUPPORT_CFGUPDATE_H
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#define LLVM_SUPPORT_CFGUPDATE_H
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#include "llvm/ADT/APInt.h"
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/PointerIntPair.h"
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#include "llvm/Support/Compiler.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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namespace llvm {
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namespace cfg {
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enum class UpdateKind : unsigned char { Insert, Delete };
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template <typename NodePtr> class Update {
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using NodeKindPair = PointerIntPair<NodePtr, 1, UpdateKind>;
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NodePtr From;
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NodeKindPair ToAndKind;
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public:
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Update(UpdateKind Kind, NodePtr From, NodePtr To)
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: From(From), ToAndKind(To, Kind) {}
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UpdateKind getKind() const { return ToAndKind.getInt(); }
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NodePtr getFrom() const { return From; }
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NodePtr getTo() const { return ToAndKind.getPointer(); }
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bool operator==(const Update &RHS) const {
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return From == RHS.From && ToAndKind == RHS.ToAndKind;
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}
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void print(raw_ostream &OS) const {
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OS << (getKind() == UpdateKind::Insert ? "Insert " : "Delete ");
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getFrom()->printAsOperand(OS, false);
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OS << " -> ";
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getTo()->printAsOperand(OS, false);
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}
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#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
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LLVM_DUMP_METHOD void dump() const { print(dbgs()); }
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#endif
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};
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// LegalizeUpdates function simplifies updates assuming a graph structure.
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// This function serves double purpose:
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// a) It removes redundant updates, which makes it easier to reverse-apply
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// them when traversing CFG.
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// b) It optimizes away updates that cancel each other out, as the end result
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// is the same.
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template <typename NodePtr>
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void LegalizeUpdates(ArrayRef<Update<NodePtr>> AllUpdates,
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SmallVectorImpl<Update<NodePtr>> &Result,
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bool InverseGraph) {
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// Count the total number of inserions of each edge.
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// Each insertion adds 1 and deletion subtracts 1. The end number should be
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// one of {-1 (deletion), 0 (NOP), +1 (insertion)}. Otherwise, the sequence
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// of updates contains multiple updates of the same kind and we assert for
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// that case.
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SmallDenseMap<std::pair<NodePtr, NodePtr>, int, 4> Operations;
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Operations.reserve(AllUpdates.size());
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for (const auto &U : AllUpdates) {
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NodePtr From = U.getFrom();
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NodePtr To = U.getTo();
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if (InverseGraph)
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std::swap(From, To); // Reverse edge for postdominators.
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Operations[{From, To}] += (U.getKind() == UpdateKind::Insert ? 1 : -1);
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}
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Result.clear();
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Result.reserve(Operations.size());
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for (auto &Op : Operations) {
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const int NumInsertions = Op.second;
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assert(std::abs(NumInsertions) <= 1 && "Unbalanced operations!");
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if (NumInsertions == 0)
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continue;
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const UpdateKind UK =
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NumInsertions > 0 ? UpdateKind::Insert : UpdateKind::Delete;
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Result.push_back({UK, Op.first.first, Op.first.second});
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}
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// Make the order consistent by not relying on pointer values within the
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// set. Reuse the old Operations map.
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// In the future, we should sort by something else to minimize the amount
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// of work needed to perform the series of updates.
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for (size_t i = 0, e = AllUpdates.size(); i != e; ++i) {
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const auto &U = AllUpdates[i];
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if (!InverseGraph)
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Operations[{U.getFrom(), U.getTo()}] = int(i);
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else
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Operations[{U.getTo(), U.getFrom()}] = int(i);
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}
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llvm::sort(Result,
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[&Operations](const Update<NodePtr> &A, const Update<NodePtr> &B) {
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return Operations[{A.getFrom(), A.getTo()}] >
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Operations[{B.getFrom(), B.getTo()}];
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});
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}
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} // end namespace cfg
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} // end namespace llvm
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#endif // LLVM_SUPPORT_CFGUPDATE_H
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