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//===- 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
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