ScalarEvolutionExpander.h revision e922c0201916e0b980ab3cfe91e1413e68d55647 
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/Analysis/ScalarEvolutionExpressions.h"
18#include "llvm/Support/IRBuilder.h"
19#include "llvm/Support/TargetFolder.h"
20#include <set>
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<std::pair<const SCEV *, Instruction *>, AssertingVH<Value> >
32      InsertedExpressions;
33    std::set<Value*> InsertedValues;
34
35    typedef IRBuilder<true, TargetFolder> BuilderType;
36    BuilderType Builder;
37
38    friend struct SCEVVisitor<SCEVExpander, Value*>;
39  public:
40    explicit SCEVExpander(ScalarEvolution &se)
41      : SE(se), Builder(se.getContext(),
42                        TargetFolder(se.TD, se.getContext())) {}
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    /// getOrInsertCanonicalInductionVariable - This method returns the
50    /// canonical induction variable of the specified type for the specified
51    /// loop (inserting one if there is none).  A canonical induction variable
52    /// starts at zero and steps by one on each iteration.
53    Value *getOrInsertCanonicalInductionVariable(const Loop *L, const Type *Ty);
54
55    /// expandCodeFor - Insert code to directly compute the specified SCEV
56    /// expression into the program.  The inserted code is inserted into the
57    /// specified block.
58    Value *expandCodeFor(const SCEV *SH, const Type *Ty, Instruction *IP) {
59      Builder.SetInsertPoint(IP->getParent(), IP);
60      return expandCodeFor(SH, Ty);
61    }
62
63  private:
64    LLVMContext &getContext() const { return SE.getContext(); }
65
66    /// InsertBinop - Insert the specified binary operator, doing a small amount
67    /// of work to avoid inserting an obviously redundant operation.
68    Value *InsertBinop(Instruction::BinaryOps Opcode, Value *LHS, Value *RHS);
69
70    /// InsertNoopCastOfTo - Insert a cast of V to the specified type,
71    /// which must be possible with a noop cast, doing what we can to
72    /// share the casts.
73    Value *InsertNoopCastOfTo(Value *V, const Type *Ty);
74
75    /// expandAddToGEP - Expand a SCEVAddExpr with a pointer type into a GEP
76    /// instead of using ptrtoint+arithmetic+inttoptr.
77    Value *expandAddToGEP(const SCEV *const *op_begin,
78                          const SCEV *const *op_end,
79                          const PointerType *PTy, const Type *Ty, Value *V);
80
81    Value *expand(const SCEV *S);
82
83    /// expandCodeFor - Insert code to directly compute the specified SCEV
84    /// expression into the program.  The inserted code is inserted into the
85    /// SCEVExpander's current insertion point. If a type is specified, the
86    /// result will be expanded to have that type, with a cast if necessary.
87    Value *expandCodeFor(const SCEV *SH, const Type *Ty = 0);
88
89    /// isInsertedInstruction - Return true if the specified instruction was
90    /// inserted by the code rewriter.  If so, the client should not modify the
91    /// instruction.
92    bool isInsertedInstruction(Instruction *I) const {
93      return InsertedValues.count(I);
94    }
95
96    Value *visitConstant(const SCEVConstant *S) {
97      return S->getValue();
98    }
99
100    Value *visitTruncateExpr(const SCEVTruncateExpr *S);
101
102    Value *visitZeroExtendExpr(const SCEVZeroExtendExpr *S);
103
104    Value *visitSignExtendExpr(const SCEVSignExtendExpr *S);
105
106    Value *visitAddExpr(const SCEVAddExpr *S);
107
108    Value *visitMulExpr(const SCEVMulExpr *S);
109
110    Value *visitUDivExpr(const SCEVUDivExpr *S);
111
112    Value *visitAddRecExpr(const SCEVAddRecExpr *S);
113
114    Value *visitSMaxExpr(const SCEVSMaxExpr *S);
115
116    Value *visitUMaxExpr(const SCEVUMaxExpr *S);
117
118    Value *visitUnknown(const SCEVUnknown *S) {
119      return S->getValue();
120    }
121  };
122}
123
124#endif
125
126