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