1 //===- PredIteratorCache.h - pred_iterator Cache ----------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines the PredIteratorCache class.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_IR_PREDITERATORCACHE_H
15 #define LLVM_IR_PREDITERATORCACHE_H
17 #include "llvm/ADT/ArrayRef.h"
18 #include "llvm/ADT/DenseMap.h"
19 #include "llvm/ADT/SmallVector.h"
20 #include "llvm/IR/CFG.h"
21 #include "llvm/Support/Allocator.h"
25 /// PredIteratorCache - This class is an extremely trivial cache for
26 /// predecessor iterator queries. This is useful for code that repeatedly
27 /// wants the predecessor list for the same blocks.
28 class PredIteratorCache {
29 /// BlockToPredsMap - Pointer to null-terminated list.
30 DenseMap<BasicBlock *, BasicBlock **> BlockToPredsMap;
31 DenseMap<BasicBlock *, unsigned> BlockToPredCountMap;
33 /// Memory - This is the space that holds cached preds.
34 BumpPtrAllocator Memory;
37 /// GetPreds - Get a cached list for the null-terminated predecessor list of
38 /// the specified block. This can be used in a loop like this:
39 /// for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI)
42 /// for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
43 BasicBlock **GetPreds(BasicBlock *BB) {
44 BasicBlock **&Entry = BlockToPredsMap[BB];
48 SmallVector<BasicBlock *, 32> PredCache(pred_begin(BB), pred_end(BB));
49 PredCache.push_back(nullptr); // null terminator.
51 BlockToPredCountMap[BB] = PredCache.size() - 1;
53 Entry = Memory.Allocate<BasicBlock *>(PredCache.size());
54 std::copy(PredCache.begin(), PredCache.end(), Entry);
58 unsigned GetNumPreds(BasicBlock *BB) {
60 return BlockToPredCountMap[BB];
64 size_t size(BasicBlock *BB) { return GetNumPreds(BB); }
65 ArrayRef<BasicBlock *> get(BasicBlock *BB) {
66 return makeArrayRef(GetPreds(BB), GetNumPreds(BB));
69 /// clear - Remove all information.
71 BlockToPredsMap.clear();
72 BlockToPredCountMap.clear();
77 } // end namespace llvm