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      1 //===- SSAUpdaterBulk.h - Unstructured SSA Update Tool ----------*- C++ -*-===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // This file declares the SSAUpdaterBulk class.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #ifndef LLVM_TRANSFORMS_UTILS_SSAUPDATERBULK_H
     15 #define LLVM_TRANSFORMS_UTILS_SSAUPDATERBULK_H
     16 
     17 #include "llvm/ADT/DenseMap.h"
     18 #include "llvm/ADT/SmallPtrSet.h"
     19 #include "llvm/ADT/StringRef.h"
     20 #include "llvm/IR/PredIteratorCache.h"
     21 
     22 namespace llvm {
     23 
     24 class BasicBlock;
     25 class PHINode;
     26 template <typename T> class SmallVectorImpl;
     27 class Type;
     28 class Use;
     29 class Value;
     30 class DominatorTree;
     31 
     32 /// Helper class for SSA formation on a set of values defined in multiple
     33 /// blocks.
     34 ///
     35 /// This is used when code duplication or another unstructured transformation
     36 /// wants to rewrite a set of uses of one value with uses of a set of values.
     37 /// The update is done only when RewriteAllUses is called, all other methods are
     38 /// used for book-keeping. That helps to share some common computations between
     39 /// updates of different uses (which is not the case when traditional SSAUpdater
     40 /// is used).
     41 class SSAUpdaterBulk {
     42   struct RewriteInfo {
     43     DenseMap<BasicBlock *, Value *> Defines;
     44     SmallVector<Use *, 4> Uses;
     45     StringRef Name;
     46     Type *Ty;
     47     RewriteInfo(){};
     48     RewriteInfo(StringRef &N, Type *T) : Name(N), Ty(T){};
     49   };
     50   SmallVector<RewriteInfo, 4> Rewrites;
     51 
     52   PredIteratorCache PredCache;
     53 
     54   Value *computeValueAt(BasicBlock *BB, RewriteInfo &R, DominatorTree *DT);
     55 
     56 public:
     57   explicit SSAUpdaterBulk(){};
     58   SSAUpdaterBulk(const SSAUpdaterBulk &) = delete;
     59   SSAUpdaterBulk &operator=(const SSAUpdaterBulk &) = delete;
     60   ~SSAUpdaterBulk(){};
     61 
     62   /// Add a new variable to the SSA rewriter. This needs to be called before
     63   /// AddAvailableValue or AddUse calls. The return value is the variable ID,
     64   /// which needs to be passed to AddAvailableValue and AddUse.
     65   unsigned AddVariable(StringRef Name, Type *Ty);
     66 
     67   /// Indicate that a rewritten value is available in the specified block with
     68   /// the specified value.
     69   void AddAvailableValue(unsigned Var, BasicBlock *BB, Value *V);
     70 
     71   /// Record a use of the symbolic value. This use will be updated with a
     72   /// rewritten value when RewriteAllUses is called.
     73   void AddUse(unsigned Var, Use *U);
     74 
     75   /// Return true if the SSAUpdater already has a value for the specified
     76   /// variable in the specified block.
     77   bool HasValueForBlock(unsigned Var, BasicBlock *BB);
     78 
     79   /// Perform all the necessary updates, including new PHI-nodes insertion and
     80   /// the requested uses update.
     81   ///
     82   /// The function requires dominator tree DT, which is used for computing
     83   /// locations for new phi-nodes insertions. If a nonnull pointer to a vector
     84   /// InsertedPHIs is passed, all the new phi-nodes will be added to this
     85   /// vector.
     86   void RewriteAllUses(DominatorTree *DT,
     87                       SmallVectorImpl<PHINode *> *InsertedPHIs = nullptr);
     88 };
     89 
     90 } // end namespace llvm
     91 
     92 #endif // LLVM_TRANSFORMS_UTILS_SSAUPDATERBULK_H
     93