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93 lines
3.0 KiB
C++
93 lines
3.0 KiB
C++
//===- SyncDependenceAnalysis.h - Divergent Branch Dependence -*- 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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// \file
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// This file defines the SyncDependenceAnalysis class, which computes for
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// every divergent branch the set of phi nodes that the branch will make
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// divergent.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ANALYSIS_SYNCDEPENDENCEANALYSIS_H
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#define LLVM_ANALYSIS_SYNCDEPENDENCEANALYSIS_H
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/PostOrderIterator.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/Analysis/LoopInfo.h"
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#include <memory>
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#include <unordered_map>
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namespace llvm {
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class BasicBlock;
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class DominatorTree;
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class Loop;
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class PostDominatorTree;
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using ConstBlockSet = SmallPtrSet<const BasicBlock *, 4>;
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struct ControlDivergenceDesc {
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// Join points of divergent disjoint paths.
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ConstBlockSet JoinDivBlocks;
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// Divergent loop exits
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ConstBlockSet LoopDivBlocks;
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};
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struct ModifiedPO {
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std::vector<const BasicBlock *> LoopPO;
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std::unordered_map<const BasicBlock *, unsigned> POIndex;
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void appendBlock(const BasicBlock &BB) {
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POIndex[&BB] = LoopPO.size();
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LoopPO.push_back(&BB);
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}
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unsigned getIndexOf(const BasicBlock &BB) const {
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return POIndex.find(&BB)->second;
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}
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unsigned size() const { return LoopPO.size(); }
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const BasicBlock *getBlockAt(unsigned Idx) const { return LoopPO[Idx]; }
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};
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/// \brief Relates points of divergent control to join points in
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/// reducible CFGs.
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///
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/// This analysis relates points of divergent control to points of converging
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/// divergent control. The analysis requires all loops to be reducible.
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class SyncDependenceAnalysis {
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public:
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~SyncDependenceAnalysis();
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SyncDependenceAnalysis(const DominatorTree &DT, const PostDominatorTree &PDT,
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const LoopInfo &LI);
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/// \brief Computes divergent join points and loop exits caused by branch
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/// divergence in \p Term.
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///
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/// The set of blocks which are reachable by disjoint paths from \p Term.
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/// The set also contains loop exits if there two disjoint paths:
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/// one from \p Term to the loop exit and another from \p Term to the loop
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/// header. Those exit blocks are added to the returned set.
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/// If L is the parent loop of \p Term and an exit of L is in the returned
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/// set then L is a divergent loop.
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const ControlDivergenceDesc &getJoinBlocks(const Instruction &Term);
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private:
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static ControlDivergenceDesc EmptyDivergenceDesc;
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ModifiedPO LoopPO;
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const DominatorTree &DT;
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const PostDominatorTree &PDT;
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const LoopInfo &LI;
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std::map<const Instruction *, std::unique_ptr<ControlDivergenceDesc>>
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CachedControlDivDescs;
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};
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} // namespace llvm
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#endif // LLVM_ANALYSIS_SYNCDEPENDENCEANALYSIS_H
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