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//===- llvm/Support/PredIteratorCache.h - pred_iterator Cache ---*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the PredIteratorCache class.
//
//===----------------------------------------------------------------------===//
#include "llvm/Support/Allocator.h"
#include "llvm/Support/CFG.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallVector.h"
#ifndef LLVM_SUPPORT_PREDITERATORCACHE_H
#define LLVM_SUPPORT_PREDITERATORCACHE_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.
DenseMap<BasicBlock*, BasicBlock**> BlockToPredsMap;
DenseMap<BasicBlock*, unsigned> BlockToPredCountMap;
/// Memory - This is the space that holds cached preds.
BumpPtrAllocator Memory;
public:
/// 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(0); // 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) {
GetPreds(BB);
return BlockToPredCountMap[BB];
}
/// clear - Remove all information.
void clear() {
BlockToPredsMap.clear();
BlockToPredCountMap.clear();
Memory.Reset();
}
};
} // end namespace llvm
#endif
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