| //===- DomTreeUpdater.h - DomTree/Post DomTree Updater ----------*- 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 |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file defines the DomTreeUpdater class, which provides a uniform way to |
| // update dominator tree related data structures. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLVM_ANALYSIS_DOMTREEUPDATER_H |
| #define LLVM_ANALYSIS_DOMTREEUPDATER_H |
| |
| #include "llvm/ADT/SmallPtrSet.h" |
| #include "llvm/IR/Dominators.h" |
| #include "llvm/IR/ValueHandle.h" |
| #include "llvm/Support/Compiler.h" |
| #include <cstddef> |
| #include <functional> |
| #include <vector> |
| |
| namespace llvm { |
| class PostDominatorTree; |
| |
| class DomTreeUpdater { |
| public: |
| enum class UpdateStrategy : unsigned char { Eager = 0, Lazy = 1 }; |
| |
| explicit DomTreeUpdater(UpdateStrategy Strategy_) : Strategy(Strategy_) {} |
| DomTreeUpdater(DominatorTree &DT_, UpdateStrategy Strategy_) |
| : DT(&DT_), Strategy(Strategy_) {} |
| DomTreeUpdater(DominatorTree *DT_, UpdateStrategy Strategy_) |
| : DT(DT_), Strategy(Strategy_) {} |
| DomTreeUpdater(PostDominatorTree &PDT_, UpdateStrategy Strategy_) |
| : PDT(&PDT_), Strategy(Strategy_) {} |
| DomTreeUpdater(PostDominatorTree *PDT_, UpdateStrategy Strategy_) |
| : PDT(PDT_), Strategy(Strategy_) {} |
| DomTreeUpdater(DominatorTree &DT_, PostDominatorTree &PDT_, |
| UpdateStrategy Strategy_) |
| : DT(&DT_), PDT(&PDT_), Strategy(Strategy_) {} |
| DomTreeUpdater(DominatorTree *DT_, PostDominatorTree *PDT_, |
| UpdateStrategy Strategy_) |
| : DT(DT_), PDT(PDT_), Strategy(Strategy_) {} |
| |
| ~DomTreeUpdater() { flush(); } |
| |
| /// Returns true if the current strategy is Lazy. |
| bool isLazy() const { return Strategy == UpdateStrategy::Lazy; }; |
| |
| /// Returns true if the current strategy is Eager. |
| bool isEager() const { return Strategy == UpdateStrategy::Eager; }; |
| |
| /// Returns true if it holds a DominatorTree. |
| bool hasDomTree() const { return DT != nullptr; } |
| |
| /// Returns true if it holds a PostDominatorTree. |
| bool hasPostDomTree() const { return PDT != nullptr; } |
| |
| /// Returns true if there is BasicBlock awaiting deletion. |
| /// The deletion will only happen until a flush event and |
| /// all available trees are up-to-date. |
| /// Returns false under Eager UpdateStrategy. |
| bool hasPendingDeletedBB() const { return !DeletedBBs.empty(); } |
| |
| /// Returns true if DelBB is awaiting deletion. |
| /// Returns false under Eager UpdateStrategy. |
| bool isBBPendingDeletion(BasicBlock *DelBB) const; |
| |
| /// Returns true if either of DT or PDT is valid and the tree has at |
| /// least one update pending. If DT or PDT is nullptr it is treated |
| /// as having no pending updates. This function does not check |
| /// whether there is BasicBlock awaiting deletion. |
| /// Returns false under Eager UpdateStrategy. |
| bool hasPendingUpdates() const; |
| |
| /// Returns true if there are DominatorTree updates queued. |
| /// Returns false under Eager UpdateStrategy or DT is nullptr. |
| bool hasPendingDomTreeUpdates() const; |
| |
| /// Returns true if there are PostDominatorTree updates queued. |
| /// Returns false under Eager UpdateStrategy or PDT is nullptr. |
| bool hasPendingPostDomTreeUpdates() const; |
| |
| ///@{ |
| /// \name Mutation APIs |
| /// |
| /// These methods provide APIs for submitting updates to the DominatorTree and |
| /// the PostDominatorTree. |
| /// |
| /// Note: There are two strategies to update the DominatorTree and the |
| /// PostDominatorTree: |
| /// 1. Eager UpdateStrategy: Updates are submitted and then flushed |
| /// immediately. |
| /// 2. Lazy UpdateStrategy: Updates are submitted but only flushed when you |
| /// explicitly call Flush APIs. It is recommended to use this update strategy |
| /// when you submit a bunch of updates multiple times which can then |
| /// add up to a large number of updates between two queries on the |
| /// DominatorTree. The incremental updater can reschedule the updates or |
| /// decide to recalculate the dominator tree in order to speedup the updating |
| /// process depending on the number of updates. |
| /// |
| /// Although GenericDomTree provides several update primitives, |
| /// it is not encouraged to use these APIs directly. |
| |
| /// Submit updates to all available trees. |
| /// The Eager Strategy flushes updates immediately while the Lazy Strategy |
| /// queues the updates. |
| /// |
| /// Note: The "existence" of an edge in a CFG refers to the CFG which DTU is |
| /// in sync with + all updates before that single update. |
| /// |
| /// CAUTION! |
| /// 1. It is required for the state of the LLVM IR to be updated |
| /// *before* submitting the updates because the internal update routine will |
| /// analyze the current state of the CFG to determine whether an update |
| /// is valid. |
| /// 2. It is illegal to submit any update that has already been submitted, |
| /// i.e., you are supposed not to insert an existent edge or delete a |
| /// nonexistent edge. |
| void applyUpdates(ArrayRef<DominatorTree::UpdateType> Updates); |
| |
| /// Submit updates to all available trees. It will also |
| /// 1. discard duplicated updates, |
| /// 2. remove invalid updates. (Invalid updates means deletion of an edge that |
| /// still exists or insertion of an edge that does not exist.) |
| /// The Eager Strategy flushes updates immediately while the Lazy Strategy |
| /// queues the updates. |
| /// |
| /// Note: The "existence" of an edge in a CFG refers to the CFG which DTU is |
| /// in sync with + all updates before that single update. |
| /// |
| /// CAUTION! |
| /// 1. It is required for the state of the LLVM IR to be updated |
| /// *before* submitting the updates because the internal update routine will |
| /// analyze the current state of the CFG to determine whether an update |
| /// is valid. |
| /// 2. It is illegal to submit any update that has already been submitted, |
| /// i.e., you are supposed not to insert an existent edge or delete a |
| /// nonexistent edge. |
| /// 3. It is only legal to submit updates to an edge in the order CFG changes |
| /// are made. The order you submit updates on different edges is not |
| /// restricted. |
| void applyUpdatesPermissive(ArrayRef<DominatorTree::UpdateType> Updates); |
| |
| /// Notify DTU that the entry block was replaced. |
| /// Recalculate all available trees and flush all BasicBlocks |
| /// awaiting deletion immediately. |
| void recalculate(Function &F); |
| |
| /// Delete DelBB. DelBB will be removed from its Parent and |
| /// erased from available trees if it exists and finally get deleted. |
| /// Under Eager UpdateStrategy, DelBB will be processed immediately. |
| /// Under Lazy UpdateStrategy, DelBB will be queued until a flush event and |
| /// all available trees are up-to-date. Assert if any instruction of DelBB is |
| /// modified while awaiting deletion. When both DT and PDT are nullptrs, DelBB |
| /// will be queued until flush() is called. |
| void deleteBB(BasicBlock *DelBB); |
| |
| /// Delete DelBB. DelBB will be removed from its Parent and |
| /// erased from available trees if it exists. Then the callback will |
| /// be called. Finally, DelBB will be deleted. |
| /// Under Eager UpdateStrategy, DelBB will be processed immediately. |
| /// Under Lazy UpdateStrategy, DelBB will be queued until a flush event and |
| /// all available trees are up-to-date. Assert if any instruction of DelBB is |
| /// modified while awaiting deletion. Multiple callbacks can be queued for one |
| /// DelBB under Lazy UpdateStrategy. |
| void callbackDeleteBB(BasicBlock *DelBB, |
| std::function<void(BasicBlock *)> Callback); |
| |
| ///@} |
| |
| ///@{ |
| /// \name Flush APIs |
| /// |
| /// CAUTION! By the moment these flush APIs are called, the current CFG needs |
| /// to be the same as the CFG which DTU is in sync with + all updates |
| /// submitted. |
| |
| /// Flush DomTree updates and return DomTree. |
| /// It flushes Deleted BBs if both trees are up-to-date. |
| /// It must only be called when it has a DomTree. |
| DominatorTree &getDomTree(); |
| |
| /// Flush PostDomTree updates and return PostDomTree. |
| /// It flushes Deleted BBs if both trees are up-to-date. |
| /// It must only be called when it has a PostDomTree. |
| PostDominatorTree &getPostDomTree(); |
| |
| /// Apply all pending updates to available trees and flush all BasicBlocks |
| /// awaiting deletion. |
| |
| void flush(); |
| |
| ///@} |
| |
| /// Debug method to help view the internal state of this class. |
| LLVM_DUMP_METHOD void dump() const; |
| |
| private: |
| class CallBackOnDeletion final : public CallbackVH { |
| public: |
| CallBackOnDeletion(BasicBlock *V, |
| std::function<void(BasicBlock *)> Callback) |
| : CallbackVH(V), DelBB(V), Callback_(Callback) {} |
| |
| private: |
| BasicBlock *DelBB = nullptr; |
| std::function<void(BasicBlock *)> Callback_; |
| |
| void deleted() override { |
| Callback_(DelBB); |
| CallbackVH::deleted(); |
| } |
| }; |
| |
| SmallVector<DominatorTree::UpdateType, 16> PendUpdates; |
| size_t PendDTUpdateIndex = 0; |
| size_t PendPDTUpdateIndex = 0; |
| DominatorTree *DT = nullptr; |
| PostDominatorTree *PDT = nullptr; |
| const UpdateStrategy Strategy; |
| SmallPtrSet<BasicBlock *, 8> DeletedBBs; |
| std::vector<CallBackOnDeletion> Callbacks; |
| bool IsRecalculatingDomTree = false; |
| bool IsRecalculatingPostDomTree = false; |
| |
| /// First remove all the instructions of DelBB and then make sure DelBB has a |
| /// valid terminator instruction which is necessary to have when DelBB still |
| /// has to be inside of its parent Function while awaiting deletion under Lazy |
| /// UpdateStrategy to prevent other routines from asserting the state of the |
| /// IR is inconsistent. Assert if DelBB is nullptr or has predecessors. |
| void validateDeleteBB(BasicBlock *DelBB); |
| |
| /// Returns true if at least one BasicBlock is deleted. |
| bool forceFlushDeletedBB(); |
| |
| /// Helper function to apply all pending DomTree updates. |
| void applyDomTreeUpdates(); |
| |
| /// Helper function to apply all pending PostDomTree updates. |
| void applyPostDomTreeUpdates(); |
| |
| /// Helper function to flush deleted BasicBlocks if all available |
| /// trees are up-to-date. |
| void tryFlushDeletedBB(); |
| |
| /// Drop all updates applied by all available trees and delete BasicBlocks if |
| /// all available trees are up-to-date. |
| void dropOutOfDateUpdates(); |
| |
| /// Erase Basic Block node that has been unlinked from Function |
| /// in the DomTree and PostDomTree. |
| void eraseDelBBNode(BasicBlock *DelBB); |
| |
| /// Returns true if the update appears in the LLVM IR. |
| /// It is used to check whether an update is valid in |
| /// insertEdge/deleteEdge or is unnecessary in the batch update. |
| bool isUpdateValid(DominatorTree::UpdateType Update) const; |
| |
| /// Returns true if the update is self dominance. |
| bool isSelfDominance(DominatorTree::UpdateType Update) const; |
| }; |
| } // namespace llvm |
| |
| #endif // LLVM_ANALYSIS_DOMTREEUPDATER_H |