| //===- PredIteratorCache.h - pred_iterator Cache ----------------*- C++ -*-===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file defines the PredIteratorCache class. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLVM_IR_PREDITERATORCACHE_H |
| #define LLVM_IR_PREDITERATORCACHE_H |
| |
| #include "llvm/ADT/ArrayRef.h" |
| #include "llvm/ADT/DenseMap.h" |
| #include "llvm/ADT/SmallVector.h" |
| #include "llvm/IR/CFG.h" |
| #include "llvm/Support/Allocator.h" |
| |
| namespace llvm { |
| |
| /// PredIteratorCache - This class is an extremely trivial cache for |
| /// predecessor iterator queries. This is useful for code that repeatedly |
| /// wants the predecessor list for the same blocks. |
| class PredIteratorCache { |
| /// BlockToPredsMap - Pointer to null-terminated list. |
| mutable DenseMap<BasicBlock *, BasicBlock **> BlockToPredsMap; |
| mutable DenseMap<BasicBlock *, unsigned> BlockToPredCountMap; |
| |
| /// Memory - This is the space that holds cached preds. |
| BumpPtrAllocator Memory; |
| |
| private: |
| /// GetPreds - Get a cached list for the null-terminated predecessor list of |
| /// the specified block. This can be used in a loop like this: |
| /// for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) |
| /// use(*PI); |
| /// instead of: |
| /// for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) |
| BasicBlock **GetPreds(BasicBlock *BB) { |
| BasicBlock **&Entry = BlockToPredsMap[BB]; |
| if (Entry) |
| return Entry; |
| |
| SmallVector<BasicBlock *, 32> PredCache(pred_begin(BB), pred_end(BB)); |
| PredCache.push_back(nullptr); // null terminator. |
| |
| BlockToPredCountMap[BB] = PredCache.size() - 1; |
| |
| Entry = Memory.Allocate<BasicBlock *>(PredCache.size()); |
| std::copy(PredCache.begin(), PredCache.end(), Entry); |
| return Entry; |
| } |
| |
| unsigned GetNumPreds(BasicBlock *BB) const { |
| auto Result = BlockToPredCountMap.find(BB); |
| if (Result != BlockToPredCountMap.end()) |
| return Result->second; |
| return BlockToPredCountMap[BB] = std::distance(pred_begin(BB), pred_end(BB)); |
| } |
| |
| public: |
| size_t size(BasicBlock *BB) const { return GetNumPreds(BB); } |
| ArrayRef<BasicBlock *> get(BasicBlock *BB) { |
| return makeArrayRef(GetPreds(BB), GetNumPreds(BB)); |
| } |
| |
| /// clear - Remove all information. |
| void clear() { |
| BlockToPredsMap.clear(); |
| BlockToPredCountMap.clear(); |
| Memory.Reset(); |
| } |
| }; |
| |
| } // end namespace llvm |
| |
| #endif |