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to reflect the new license. We understand that people may be surprised that we're moving the header entirely to discuss the new license. We checked this carefully with the Foundation's lawyer and we believe this is the correct approach. Essentially, all code in the project is now made available by the LLVM project under our new license, so you will see that the license headers include that license only. Some of our contributors have contributed code under our old license, and accordingly, we have retained a copy of our old license notice in the top-level files in each project and repository. llvm-svn: 351636
81 lines
2.6 KiB
C++
81 lines
2.6 KiB
C++
//===- PredIteratorCache.h - pred_iterator Cache ----------------*- 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 defines the PredIteratorCache class.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_IR_PREDITERATORCACHE_H
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#define LLVM_IR_PREDITERATORCACHE_H
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#include "llvm/ADT/ArrayRef.h"
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/IR/CFG.h"
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#include "llvm/Support/Allocator.h"
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namespace llvm {
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/// PredIteratorCache - This class is an extremely trivial cache for
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/// predecessor iterator queries. This is useful for code that repeatedly
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/// wants the predecessor list for the same blocks.
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class PredIteratorCache {
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/// BlockToPredsMap - Pointer to null-terminated list.
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mutable DenseMap<BasicBlock *, BasicBlock **> BlockToPredsMap;
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mutable DenseMap<BasicBlock *, unsigned> BlockToPredCountMap;
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/// Memory - This is the space that holds cached preds.
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BumpPtrAllocator Memory;
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private:
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/// GetPreds - Get a cached list for the null-terminated predecessor list of
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/// the specified block. This can be used in a loop like this:
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/// for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI)
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/// use(*PI);
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/// instead of:
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/// for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
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BasicBlock **GetPreds(BasicBlock *BB) {
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BasicBlock **&Entry = BlockToPredsMap[BB];
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if (Entry)
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return Entry;
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SmallVector<BasicBlock *, 32> PredCache(pred_begin(BB), pred_end(BB));
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PredCache.push_back(nullptr); // null terminator.
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BlockToPredCountMap[BB] = PredCache.size() - 1;
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Entry = Memory.Allocate<BasicBlock *>(PredCache.size());
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std::copy(PredCache.begin(), PredCache.end(), Entry);
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return Entry;
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}
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unsigned GetNumPreds(BasicBlock *BB) const {
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auto Result = BlockToPredCountMap.find(BB);
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if (Result != BlockToPredCountMap.end())
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return Result->second;
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return BlockToPredCountMap[BB] = std::distance(pred_begin(BB), pred_end(BB));
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}
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public:
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size_t size(BasicBlock *BB) const { return GetNumPreds(BB); }
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ArrayRef<BasicBlock *> get(BasicBlock *BB) {
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return makeArrayRef(GetPreds(BB), GetNumPreds(BB));
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}
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/// clear - Remove all information.
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void clear() {
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BlockToPredsMap.clear();
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BlockToPredCountMap.clear();
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Memory.Reset();
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}
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};
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} // end namespace llvm
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#endif
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