81 lines
2.5 KiB
C
81 lines
2.5 KiB
C
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//===- 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(predecessors(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] = pred_size(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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