117 lines
3.7 KiB
C++
117 lines
3.7 KiB
C++
//===- DomTreeUpdater.cpp - DomTree/Post DomTree Updater --------*- 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 implements the DomTreeUpdater class, which provides a uniform way
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// to update dominator tree related data structures.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/DomTreeUpdater.h"
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#include "llvm/Analysis/GenericDomTreeUpdaterImpl.h"
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#include "llvm/Analysis/PostDominators.h"
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#include "llvm/IR/Constants.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/Support/GenericDomTree.h"
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#include <functional>
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namespace llvm {
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template class GenericDomTreeUpdater<DomTreeUpdater, DominatorTree,
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PostDominatorTree>;
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template void
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GenericDomTreeUpdater<DomTreeUpdater, DominatorTree,
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PostDominatorTree>::recalculate(Function &F);
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bool DomTreeUpdater::forceFlushDeletedBB() {
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if (DeletedBBs.empty())
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return false;
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for (auto *BB : DeletedBBs) {
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// After calling deleteBB or callbackDeleteBB under Lazy UpdateStrategy,
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// validateDeleteBB() removes all instructions of DelBB and adds an
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// UnreachableInst as its terminator. So we check whether the BasicBlock to
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// delete only has an UnreachableInst inside.
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assert(BB->size() == 1 && isa<UnreachableInst>(BB->getTerminator()) &&
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"DelBB has been modified while awaiting deletion.");
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eraseDelBBNode(BB);
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BB->eraseFromParent();
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}
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DeletedBBs.clear();
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Callbacks.clear();
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return true;
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}
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// The DT and PDT require the nodes related to updates
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// are not deleted when update functions are called.
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// So BasicBlock deletions must be pended when the
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// UpdateStrategy is Lazy. When the UpdateStrategy is
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// Eager, the BasicBlock will be deleted immediately.
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void DomTreeUpdater::deleteBB(BasicBlock *DelBB) {
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validateDeleteBB(DelBB);
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if (Strategy == UpdateStrategy::Lazy) {
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DeletedBBs.insert(DelBB);
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return;
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}
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eraseDelBBNode(DelBB);
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DelBB->eraseFromParent();
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}
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void DomTreeUpdater::callbackDeleteBB(
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BasicBlock *DelBB, std::function<void(BasicBlock *)> Callback) {
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validateDeleteBB(DelBB);
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if (Strategy == UpdateStrategy::Lazy) {
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Callbacks.push_back(CallBackOnDeletion(DelBB, Callback));
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DeletedBBs.insert(DelBB);
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return;
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}
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eraseDelBBNode(DelBB);
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DelBB->removeFromParent();
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Callback(DelBB);
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delete DelBB;
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}
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void DomTreeUpdater::validateDeleteBB(BasicBlock *DelBB) {
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assert(DelBB && "Invalid push_back of nullptr DelBB.");
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assert(pred_empty(DelBB) && "DelBB has one or more predecessors.");
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// DelBB is unreachable and all its instructions are dead.
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while (!DelBB->empty()) {
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Instruction &I = DelBB->back();
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// Replace used instructions with an arbitrary value (poison).
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if (!I.use_empty())
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I.replaceAllUsesWith(PoisonValue::get(I.getType()));
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DelBB->back().eraseFromParent();
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}
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// Make sure DelBB has a valid terminator instruction. As long as DelBB is a
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// Child of Function F it must contain valid IR.
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new UnreachableInst(DelBB->getContext(), DelBB);
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}
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LLVM_DUMP_METHOD
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void DomTreeUpdater::dump() const {
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Base::dump();
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#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
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raw_ostream &OS = dbgs();
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OS << "Pending Callbacks:\n";
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int Index = 0;
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for (const auto &BB : Callbacks) {
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OS << " " << Index << " : ";
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++Index;
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if (BB->hasName())
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OS << BB->getName() << "(";
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else
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OS << "(no_name)(";
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OS << BB << ")\n";
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}
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#endif
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}
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} // namespace llvm
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