ScalarEvolutionExpander.h revision 453aa4fbf1083cc7f646a0ac21e2bcc384a91ae9 
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    std::map<SCEVHandle, AssertingVH<Value> > InsertedExpressions;
32    std::set<Value*> InsertedValues;
33
34    BasicBlock::iterator InsertPt;
35
36    friend struct SCEVVisitor<SCEVExpander, Value*>;
37  public:
38    explicit SCEVExpander(ScalarEvolution &se)
39      : SE(se) {}
40
41    /// clear - Erase the contents of the InsertedExpressions map so that users
42    /// trying to expand the same expression into multiple BasicBlocks or
43    /// different places within the same BasicBlock can do so.
44    void clear() { InsertedExpressions.clear(); }
45
46    /// isInsertedInstruction - Return true if the specified instruction was
47    /// inserted by the code rewriter.  If so, the client should not modify the
48    /// instruction.
49    bool isInsertedInstruction(Instruction *I) const {
50      return InsertedValues.count(I);
51    }
52
53    /// isInsertedExpression - Return true if the the code rewriter has a
54    /// Value* recorded for the given expression.
55    bool isInsertedExpression(const SCEV *S) const {
56      return InsertedExpressions.count(S);
57    }
58
59    /// getOrInsertCanonicalInductionVariable - This method returns the
60    /// canonical induction variable of the specified type for the specified
61    /// loop (inserting one if there is none).  A canonical induction variable
62    /// starts at zero and steps by one on each iteration.
63    Value *getOrInsertCanonicalInductionVariable(const Loop *L, const Type *Ty){
64      assert(Ty->isInteger() && "Can only insert integer induction variables!");
65      SCEVHandle H = SE.getAddRecExpr(SE.getIntegerSCEV(0, Ty),
66                                      SE.getIntegerSCEV(1, Ty), L);
67      return expand(H);
68    }
69
70    /// addInsertedValue - Remember the specified instruction as being the
71    /// canonical form for the specified SCEV.
72    void addInsertedValue(Value *V, const SCEV *S) {
73      InsertedExpressions[S] = V;
74      InsertedValues.insert(V);
75    }
76
77    void setInsertionPoint(BasicBlock::iterator NewIP) { InsertPt = NewIP; }
78
79    BasicBlock::iterator getInsertionPoint() const { return InsertPt; }
80
81    /// expandCodeFor - Insert code to directly compute the specified SCEV
82    /// expression into the program.  The inserted code is inserted into the
83    /// SCEVExpander's current insertion point. If a type is specified, the
84    /// result will be expanded to have that type, with a cast if necessary.
85    Value *expandCodeFor(SCEVHandle SH, const Type *Ty = 0);
86
87    /// expandCodeFor - Insert code to directly compute the specified SCEV
88    /// expression into the program.  The inserted code is inserted into the
89    /// specified block.
90    Value *expandCodeFor(SCEVHandle SH, const Type *Ty,
91                         BasicBlock::iterator IP) {
92      setInsertionPoint(IP);
93      return expandCodeFor(SH, Ty);
94    }
95
96    /// InsertCastOfTo - Insert a cast of V to the specified type, doing what
97    /// we can to share the casts.
98    Value *InsertCastOfTo(Instruction::CastOps opcode, Value *V,
99                          const Type *Ty);
100
101    /// InsertNoopCastOfTo - Insert a cast of V to the specified type,
102    /// which must be possible with a noop cast.
103    Value *InsertNoopCastOfTo(Value *V, const Type *Ty);
104
105    /// InsertBinop - Insert the specified binary operator, doing a small amount
106    /// of work to avoid inserting an obviously redundant operation.
107    Value *InsertBinop(Instruction::BinaryOps Opcode, Value *LHS,
108                       Value *RHS, BasicBlock::iterator InsertPt);
109
110  private:
111    /// expandAddToGEP - Expand a SCEVAddExpr with a pointer type into a GEP
112    /// instead of using ptrtoint+arithmetic+inttoptr.
113    Value *expandAddToGEP(const SCEVHandle *op_begin, const SCEVHandle *op_end,
114                          const PointerType *PTy, const Type *Ty, Value *V);
115
116    Value *expand(const SCEV *S);
117
118    Value *visitConstant(const SCEVConstant *S) {
119      return S->getValue();
120    }
121
122    Value *visitTruncateExpr(const SCEVTruncateExpr *S);
123
124    Value *visitZeroExtendExpr(const SCEVZeroExtendExpr *S);
125
126    Value *visitSignExtendExpr(const SCEVSignExtendExpr *S);
127
128    Value *visitAddExpr(const SCEVAddExpr *S);
129
130    Value *visitMulExpr(const SCEVMulExpr *S);
131
132    Value *visitUDivExpr(const SCEVUDivExpr *S);
133
134    Value *visitAddRecExpr(const SCEVAddRecExpr *S);
135
136    Value *visitSMaxExpr(const SCEVSMaxExpr *S);
137
138    Value *visitUMaxExpr(const SCEVUMaxExpr *S);
139
140    Value *visitUnknown(const SCEVUnknown *S) {
141      return S->getValue();
142    }
143  };
144}
145
146#endif
147
148