ScalarEvolutionExpander.h revision 6cdc727f2d7f68734526ef078f4632798ad40791 
1//===---- llvm/Analysis/ScalarEvolutionExpander.h - SCEV Exprs --*- 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 defines the classes used to generate code from scalar expressions.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_ANALYSIS_SCALAREVOLUTION_EXPANDER_H
15#define LLVM_ANALYSIS_SCALAREVOLUTION_EXPANDER_H
16
17#include "llvm/Instructions.h"
18#include "llvm/Type.h"
19#include "llvm/Analysis/ScalarEvolution.h"
20#include "llvm/Analysis/ScalarEvolutionExpressions.h"
21
22namespace llvm {
23  /// SCEVExpander - This class uses information about analyze scalars to
24  /// rewrite expressions in canonical form.
25  ///
26  /// Clients should create an instance of this class when rewriting is needed,
27  /// and destroy it when finished to allow the release of the associated
28  /// memory.
29  struct SCEVExpander : public SCEVVisitor<SCEVExpander, Value*> {
30    ScalarEvolution &SE;
31    LoopInfo &LI;
32    std::map<SCEVHandle, Value*> InsertedExpressions;
33    std::set<Instruction*> InsertedInstructions;
34
35    BasicBlock::iterator InsertPt;
36
37    friend struct SCEVVisitor<SCEVExpander, Value*>;
38  public:
39    SCEVExpander(ScalarEvolution &se, LoopInfo &li)
40      : SE(se), LI(li) {}
41
42    LoopInfo &getLoopInfo() const { return LI; }
43
44    /// clear - Erase the contents of the InsertedExpressions map so that users
45    /// trying to expand the same expression into multiple BasicBlocks or
46    /// different places within the same BasicBlock can do so.
47    void clear() { InsertedExpressions.clear(); }
48
49    /// isInsertedInstruction - Return true if the specified instruction was
50    /// inserted by the code rewriter.  If so, the client should not modify the
51    /// instruction.
52    bool isInsertedInstruction(Instruction *I) const {
53      return InsertedInstructions.count(I);
54    }
55
56    /// getOrInsertCanonicalInductionVariable - This method returns the
57    /// canonical induction variable of the specified type for the specified
58    /// loop (inserting one if there is none).  A canonical induction variable
59    /// starts at zero and steps by one on each iteration.
60    Value *getOrInsertCanonicalInductionVariable(const Loop *L, const Type *Ty){
61      assert(Ty->isInteger() && "Can only insert integer induction variables!");
62      SCEVHandle H = SE.getAddRecExpr(SE.getIntegerSCEV(0, Ty),
63                                      SE.getIntegerSCEV(1, Ty), L);
64      return expand(H);
65    }
66
67    /// addInsertedValue - Remember the specified instruction as being the
68    /// canonical form for the specified SCEV.
69    void addInsertedValue(Instruction *I, const SCEV *S) {
70      InsertedExpressions[S] = (Value*)I;
71      InsertedInstructions.insert(I);
72    }
73
74    BasicBlock::iterator getInsertionPoint() const { return InsertPt; }
75
76    /// expandCodeFor - Insert code to directly compute the specified SCEV
77    /// expression into the program.  The inserted code is inserted into the
78    /// specified block.
79    Value *expandCodeFor(SCEVHandle SH, const Type *Ty,
80                         BasicBlock::iterator IP);
81
82    /// InsertCastOfTo - Insert a cast of V to the specified type, doing what
83    /// we can to share the casts.
84    Value *InsertCastOfTo(Instruction::CastOps opcode, Value *V,
85                          const Type *Ty);
86
87    /// InsertNoopCastOfTo - Insert a cast of V to the specified type,
88    /// which must be possible with a noop cast.
89    Value *InsertNoopCastOfTo(Value *V, const Type *Ty);
90
91    /// InsertBinop - Insert the specified binary operator, doing a small amount
92    /// of work to avoid inserting an obviously redundant operation.
93    static Value *InsertBinop(Instruction::BinaryOps Opcode, Value *LHS,
94                              Value *RHS, BasicBlock::iterator InsertPt);
95
96  private:
97    Value *expand(const SCEV *S);
98
99    Value *visitConstant(const SCEVConstant *S) {
100      return S->getValue();
101    }
102
103    Value *visitTruncateExpr(const SCEVTruncateExpr *S);
104
105    Value *visitZeroExtendExpr(const SCEVZeroExtendExpr *S);
106
107    Value *visitSignExtendExpr(const SCEVSignExtendExpr *S);
108
109    Value *visitAddExpr(const SCEVAddExpr *S);
110
111    Value *visitMulExpr(const SCEVMulExpr *S);
112
113    Value *visitUDivExpr(const SCEVUDivExpr *S);
114
115    Value *visitAddRecExpr(const SCEVAddRecExpr *S);
116
117    Value *visitSMaxExpr(const SCEVSMaxExpr *S);
118
119    Value *visitUMaxExpr(const SCEVUMaxExpr *S);
120
121    Value *visitUnknown(const SCEVUnknown *S) {
122      return S->getValue();
123    }
124  };
125}
126
127#endif
128
129