Revamp PredIteratorCache interface to be cleaner.

Summary:
This lets us use range based for loops.

Reviewers: chandlerc

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D9169

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@235416 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/MemoryDependenceAnalysis.h

@@ -19,6 +19,7 @@
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/IR/BasicBlock.h"
+#include "llvm/IR/PredIteratorCache.h"
 #include "llvm/IR/ValueHandle.h"
 #include "llvm/Pass.h"
 
@@ -325,7 +326,7 @@ namespace llvm {
     AliasAnalysis *AA;
     DominatorTree *DT;
     AssumptionCache *AC;
-    std::unique_ptr<PredIteratorCache> PredCache;
+    PredIteratorCache PredCache;
 
   public:
     MemoryDependenceAnalysis();

include/llvm/IR/PredIteratorCache.h

@@ -14,6 +14,7 @@
 #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"
@@ -21,50 +22,58 @@
 
 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;
+/// 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:
+  /// Memory - This is the space that holds cached preds.
+  BumpPtrAllocator Memory;
 
-    /// 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);
+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;
-    }
-    
-    unsigned GetNumPreds(BasicBlock *BB) {
-      GetPreds(BB);
-      return BlockToPredCountMap[BB];
-    }
 
-    /// clear - Remove all information.
-    void clear() {
-      BlockToPredsMap.clear();
-      BlockToPredCountMap.clear();
-      Memory.Reset();
-    }
-  };
+    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) {
+    GetPreds(BB);
+    return BlockToPredCountMap[BB];
+  }
+
+public:
+  size_t size(BasicBlock *BB) { 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