1562b70eaf
This relands commit #115111.
Use traditional way to update post dominator tree, i.e. break critical
edge splitting into insert, insert, delete sequence.
When splitting critical edges, the post dominator tree may change its
root node, and `setNewRoot` only works in normal dominator tree...
See
6c7e5827ed/llvm/include/llvm/Support/GenericDomTree.h (L684-L687)
124 lines
3.9 KiB
C++
124 lines
3.9 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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template void
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GenericDomTreeUpdater<DomTreeUpdater, DominatorTree, PostDominatorTree>::
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applyUpdatesImpl</*IsForward=*/true>();
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template void
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GenericDomTreeUpdater<DomTreeUpdater, DominatorTree, PostDominatorTree>::
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applyUpdatesImpl</*IsForward=*/false>();
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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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