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71 lines
2.3 KiB
C++
71 lines
2.3 KiB
C++
//===- llvm/Support/PredIteratorCache.h - pred_iterator Cache ---*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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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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#include "llvm/Support/Allocator.h"
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#include "llvm/Support/CFG.h"
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/SmallVector.h"
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#ifndef LLVM_SUPPORT_PREDITERATORCACHE_H
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#define LLVM_SUPPORT_PREDITERATORCACHE_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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DenseMap<BasicBlock*, BasicBlock**> BlockToPredsMap;
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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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public:
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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) return Entry;
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SmallVector<BasicBlock*, 32> PredCache(pred_begin(BB), pred_end(BB));
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PredCache.push_back(0); // 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) {
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GetPreds(BB);
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return BlockToPredCountMap[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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