ScalarEvolutionExpander.h revision 8a08769bad43a22fae2845bb0ba0fd1266cd55c8 
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    Instruction *InsertPt;
36
37    friend struct SCEVVisitor<SCEVExpander, Value*>;
38  public:
39    SCEVExpander(ScalarEvolution &se, LoopInfo &li) : SE(se), LI(li) {}
40
41    LoopInfo &getLoopInfo() const { return LI; }
42
43    /// clear - Erase the contents of the InsertedExpressions map so that users
44    /// trying to expand the same expression into multiple BasicBlocks or
45    /// different places within the same BasicBlock can do so.
46    void clear() { InsertedExpressions.clear(); }
47
48    /// isInsertedInstruction - Return true if the specified instruction was
49    /// inserted by the code rewriter.  If so, the client should not modify the
50    /// instruction.
51    bool isInsertedInstruction(Instruction *I) const {
52      return InsertedInstructions.count(I);
53    }
54
55    /// getOrInsertCanonicalInductionVariable - This method returns the
56    /// canonical induction variable of the specified type for the specified
57    /// loop (inserting one if there is none).  A canonical induction variable
58    /// starts at zero and steps by one on each iteration.
59    Value *getOrInsertCanonicalInductionVariable(const Loop *L, const Type *Ty){
60      assert(Ty->isInteger() && "Can only insert integer induction variables!");
61      SCEVHandle H = SE.getAddRecExpr(SE.getIntegerSCEV(0, Ty),
62                                      SE.getIntegerSCEV(1, Ty), L);
63      return expand(H);
64    }
65
66    /// addInsertedValue - Remember the specified instruction as being the
67    /// canonical form for the specified SCEV.
68    void addInsertedValue(Instruction *I, SCEV *S) {
69      InsertedExpressions[S] = (Value*)I;
70      InsertedInstructions.insert(I);
71    }
72
73    Instruction *getInsertionPoint() const { return InsertPt; }
74
75    /// expandCodeFor - Insert code to directly compute the specified SCEV
76    /// expression into the program.  The inserted code is inserted into the
77    /// specified block.
78    Value *expandCodeFor(SCEVHandle SH, Instruction *IP) {
79      // Expand the code for this SCEV.
80      this->InsertPt = IP;
81      return expand(SH);
82    }
83
84    /// InsertCastOfTo - Insert a cast of V to the specified type, doing what
85    /// we can to share the casts.
86    static Value *InsertCastOfTo(Instruction::CastOps opcode, Value *V,
87                                 const Type *Ty);
88    /// InsertBinop - Insert the specified binary operator, doing a small amount
89    /// of work to avoid inserting an obviously redundant operation.
90    static Value *InsertBinop(Instruction::BinaryOps Opcode, Value *LHS,
91                              Value *RHS, Instruction *InsertPt);
92  protected:
93    Value *expand(SCEV *S);
94
95    Value *visitConstant(SCEVConstant *S) {
96      return S->getValue();
97    }
98
99    Value *visitTruncateExpr(SCEVTruncateExpr *S) {
100      Value *V = expand(S->getOperand());
101      return CastInst::CreateTruncOrBitCast(V, S->getType(), "tmp.", InsertPt);
102    }
103
104    Value *visitZeroExtendExpr(SCEVZeroExtendExpr *S) {
105      Value *V = expand(S->getOperand());
106      return CastInst::CreateZExtOrBitCast(V, S->getType(), "tmp.", InsertPt);
107    }
108
109    Value *visitSignExtendExpr(SCEVSignExtendExpr *S) {
110      Value *V = expand(S->getOperand());
111      return CastInst::CreateSExtOrBitCast(V, S->getType(), "tmp.", InsertPt);
112    }
113
114    Value *visitAddExpr(SCEVAddExpr *S) {
115      Value *V = expand(S->getOperand(S->getNumOperands()-1));
116
117      // Emit a bunch of add instructions
118      for (int i = S->getNumOperands()-2; i >= 0; --i)
119        V = InsertBinop(Instruction::Add, V, expand(S->getOperand(i)),
120                        InsertPt);
121      return V;
122    }
123
124    Value *visitMulExpr(SCEVMulExpr *S);
125
126    Value *visitUDivExpr(SCEVUDivExpr *S) {
127      Value *LHS = expand(S->getLHS());
128      Value *RHS = expand(S->getRHS());
129      return InsertBinop(Instruction::UDiv, LHS, RHS, InsertPt);
130    }
131
132    Value *visitAddRecExpr(SCEVAddRecExpr *S);
133
134    Value *visitSMaxExpr(SCEVSMaxExpr *S);
135
136    Value *visitUMaxExpr(SCEVUMaxExpr *S);
137
138    Value *visitUnknown(SCEVUnknown *S) {
139      return S->getValue();
140    }
141  };
142}
143
144#endif
145
146