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14 | pmbaty | 1 | //===- PredIteratorCache.h - pred_iterator Cache ----------------*- C++ -*-===// |
2 | // |
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3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
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4 | // See https://llvm.org/LICENSE.txt for license information. |
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5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
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6 | // |
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7 | //===----------------------------------------------------------------------===// |
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8 | // |
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9 | // This file defines the PredIteratorCache class. |
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10 | // |
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11 | //===----------------------------------------------------------------------===// |
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12 | |||
13 | #ifndef LLVM_IR_PREDITERATORCACHE_H |
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14 | #define LLVM_IR_PREDITERATORCACHE_H |
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15 | |||
16 | #include "llvm/ADT/ArrayRef.h" |
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17 | #include "llvm/ADT/DenseMap.h" |
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18 | #include "llvm/ADT/SmallVector.h" |
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19 | #include "llvm/IR/CFG.h" |
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20 | #include "llvm/Support/Allocator.h" |
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21 | |||
22 | namespace llvm { |
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23 | |||
24 | /// PredIteratorCache - This class is an extremely trivial cache for |
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25 | /// predecessor iterator queries. This is useful for code that repeatedly |
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26 | /// wants the predecessor list for the same blocks. |
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27 | class PredIteratorCache { |
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28 | /// BlockToPredsMap - Pointer to null-terminated list. |
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29 | mutable DenseMap<BasicBlock *, BasicBlock **> BlockToPredsMap; |
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30 | mutable DenseMap<BasicBlock *, unsigned> BlockToPredCountMap; |
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31 | |||
32 | /// Memory - This is the space that holds cached preds. |
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33 | BumpPtrAllocator Memory; |
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34 | |||
35 | private: |
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36 | /// GetPreds - Get a cached list for the null-terminated predecessor list of |
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37 | /// the specified block. This can be used in a loop like this: |
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38 | /// for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) |
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39 | /// use(*PI); |
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40 | /// instead of: |
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41 | /// for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) |
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42 | BasicBlock **GetPreds(BasicBlock *BB) { |
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43 | BasicBlock **&Entry = BlockToPredsMap[BB]; |
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44 | if (Entry) |
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45 | return Entry; |
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46 | |||
47 | SmallVector<BasicBlock *, 32> PredCache(predecessors(BB)); |
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48 | PredCache.push_back(nullptr); // null terminator. |
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49 | |||
50 | BlockToPredCountMap[BB] = PredCache.size() - 1; |
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51 | |||
52 | Entry = Memory.Allocate<BasicBlock *>(PredCache.size()); |
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53 | std::copy(PredCache.begin(), PredCache.end(), Entry); |
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54 | return Entry; |
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55 | } |
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56 | |||
57 | unsigned GetNumPreds(BasicBlock *BB) const { |
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58 | auto Result = BlockToPredCountMap.find(BB); |
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59 | if (Result != BlockToPredCountMap.end()) |
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60 | return Result->second; |
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61 | return BlockToPredCountMap[BB] = pred_size(BB); |
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62 | } |
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63 | |||
64 | public: |
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65 | size_t size(BasicBlock *BB) const { return GetNumPreds(BB); } |
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66 | ArrayRef<BasicBlock *> get(BasicBlock *BB) { |
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67 | return ArrayRef(GetPreds(BB), GetNumPreds(BB)); |
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68 | } |
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69 | |||
70 | /// clear - Remove all information. |
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71 | void clear() { |
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72 | BlockToPredsMap.clear(); |
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73 | BlockToPredCountMap.clear(); |
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74 | Memory.Reset(); |
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75 | } |
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76 | }; |
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77 | |||
78 | } // end namespace llvm |
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79 | |||
80 | #endif |