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| //===- SyncDependenceAnalysis.h - Divergent Branch Dependence -*- 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
//
//===----------------------------------------------------------------------===//
//
// \file
// This file defines the SyncDependenceAnalysis class, which computes for
// every divergent branch the set of phi nodes that the branch will make
// divergent.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_SYNC_DEPENDENCE_ANALYSIS_H
#define LLVM_ANALYSIS_SYNC_DEPENDENCE_ANALYSIS_H
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/Analysis/LoopInfo.h"
#include <memory>
namespace llvm {
class BasicBlock;
class DominatorTree;
class Loop;
class PostDominatorTree;
using ConstBlockSet = SmallPtrSet<const BasicBlock *, 4>;
/// \brief Relates points of divergent control to join points in
/// reducible CFGs.
///
/// This analysis relates points of divergent control to points of converging
/// divergent control. The analysis requires all loops to be reducible.
class SyncDependenceAnalysis {
void visitSuccessor(const BasicBlock &succBlock, const Loop *termLoop,
const BasicBlock *defBlock);
public:
bool inRegion(const BasicBlock &BB) const;
~SyncDependenceAnalysis();
SyncDependenceAnalysis(const DominatorTree &DT, const PostDominatorTree &PDT,
const LoopInfo &LI);
/// \brief Computes divergent join points and loop exits caused by branch
/// divergence in \p Term.
///
/// The set of blocks which are reachable by disjoint paths from \p Term.
/// The set also contains loop exits if there two disjoint paths:
/// one from \p Term to the loop exit and another from \p Term to the loop
/// header. Those exit blocks are added to the returned set.
/// If L is the parent loop of \p Term and an exit of L is in the returned
/// set then L is a divergent loop.
const ConstBlockSet &join_blocks(const Instruction &Term);
/// \brief Computes divergent join points and loop exits (in the surrounding
/// loop) caused by the divergent loop exits of\p Loop.
///
/// The set of blocks which are reachable by disjoint paths from the
/// loop exits of \p Loop.
/// This treats the loop as a single node in \p Loop's parent loop.
/// The returned set has the same properties as for join_blocks(TermInst&).
const ConstBlockSet &join_blocks(const Loop &Loop);
private:
static ConstBlockSet EmptyBlockSet;
ReversePostOrderTraversal<const Function *> FuncRPOT;
const DominatorTree &DT;
const PostDominatorTree &PDT;
const LoopInfo &LI;
std::map<const Loop *, std::unique_ptr<ConstBlockSet>> CachedLoopExitJoins;
std::map<const Instruction *, std::unique_ptr<ConstBlockSet>>
CachedBranchJoins;
};
} // namespace llvm
#endif // LLVM_ANALYSIS_SYNC_DEPENDENCE_ANALYSIS_H
|