include/llvm/Transforms/Utils/SSAUpdaterBulk.h

   1 //===- SSAUpdaterBulk.h - Unstructured SSA Update Tool ----------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file declares the SSAUpdaterBulk class.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #ifndef LLVM_TRANSFORMS_UTILS_SSAUPDATERBULK_H
  14 #define LLVM_TRANSFORMS_UTILS_SSAUPDATERBULK_H
  15
  16 #include "llvm/ADT/DenseMap.h"
  17 #include "llvm/ADT/SmallPtrSet.h"
  18 #include "llvm/ADT/StringRef.h"
  19 #include "llvm/IR/PredIteratorCache.h"
  20
  21 namespace llvm {
  22
  23 class BasicBlock;
  24 class PHINode;
  25 template <typename T> class SmallVectorImpl;
  26 class Type;
  27 class Use;
  28 class Value;
  29 class DominatorTree;
  30
  31 /// Helper class for SSA formation on a set of values defined in multiple
  32 /// blocks.
  33 ///
  34 /// This is used when code duplication or another unstructured transformation
  35 /// wants to rewrite a set of uses of one value with uses of a set of values.
  36 /// The update is done only when RewriteAllUses is called, all other methods are
  37 /// used for book-keeping. That helps to share some common computations between
  38 /// updates of different uses (which is not the case when traditional SSAUpdater
  39 /// is used).
  40 class SSAUpdaterBulk {
  41   struct RewriteInfo {
  42     DenseMap<BasicBlock *, Value *> Defines;
  43     SmallVector<Use *, 4> Uses;
  44     StringRef Name;
  45     Type *Ty;
  46     RewriteInfo(){};
  47     RewriteInfo(StringRef &N, Type *T) : Name(N), Ty(T){};
  48   };
  49   SmallVector<RewriteInfo, 4> Rewrites;
  50
  51   PredIteratorCache PredCache;
  52
  53   Value *computeValueAt(BasicBlock *BB, RewriteInfo &R, DominatorTree *DT);
  54
  55 public:
  56   explicit SSAUpdaterBulk(){};
  57   SSAUpdaterBulk(const SSAUpdaterBulk &) = delete;
  58   SSAUpdaterBulk &operator=(const SSAUpdaterBulk &) = delete;
  59   ~SSAUpdaterBulk(){};
  60
  61   /// Add a new variable to the SSA rewriter. This needs to be called before
  62   /// AddAvailableValue or AddUse calls. The return value is the variable ID,
  63   /// which needs to be passed to AddAvailableValue and AddUse.
  64   unsigned AddVariable(StringRef Name, Type *Ty);
  65
  66   /// Indicate that a rewritten value is available in the specified block with
  67   /// the specified value.
  68   void AddAvailableValue(unsigned Var, BasicBlock *BB, Value *V);
  69
  70   /// Record a use of the symbolic value. This use will be updated with a
  71   /// rewritten value when RewriteAllUses is called.
  72   void AddUse(unsigned Var, Use *U);
  73
  74   /// Return true if the SSAUpdater already has a value for the specified
  75   /// variable in the specified block.
  76   bool HasValueForBlock(unsigned Var, BasicBlock *BB);
  77
  78   /// Perform all the necessary updates, including new PHI-nodes insertion and
  79   /// the requested uses update.
  80   ///
  81   /// The function requires dominator tree DT, which is used for computing
  82   /// locations for new phi-nodes insertions. If a nonnull pointer to a vector
  83   /// InsertedPHIs is passed, all the new phi-nodes will be added to this
  84   /// vector.
  85   void RewriteAllUses(DominatorTree *DT,
  86                       SmallVectorImpl<PHINode *> *InsertedPHIs = nullptr);
  87 };
  88
  89 } // end namespace llvm
  90
  91 #endif // LLVM_TRANSFORMS_UTILS_SSAUPDATERBULK_H