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| Rev | Author | Line No. | Line |
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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 |