ScalarEvolutionExpander.h revision 3e6307698084e7adfc10b739442ae29742beefd0 
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/BasicBlock.h"
18#include "llvm/Constants.h"
19#include "llvm/Instructions.h"
20#include "llvm/Type.h"
21#include "llvm/Analysis/ScalarEvolution.h"
22#include "llvm/Analysis/ScalarEvolutionExpressions.h"
23#include "llvm/Support/CFG.h"
24
25namespace llvm {
26  /// SCEVExpander - This class uses information about analyze scalars to
27  /// rewrite expressions in canonical form.
28  ///
29  /// Clients should create an instance of this class when rewriting is needed,
30  /// and destroy it when finished to allow the release of the associated
31  /// memory.
32  struct SCEVExpander : public SCEVVisitor<SCEVExpander, Value*> {
33    ScalarEvolution &SE;
34    LoopInfo &LI;
35    std::map<SCEVHandle, Value*> InsertedExpressions;
36    std::set<Instruction*> InsertedInstructions;
37
38    Instruction *InsertPt;
39
40    friend struct SCEVVisitor<SCEVExpander, Value*>;
41  public:
42    SCEVExpander(ScalarEvolution &se, LoopInfo &li) : SE(se), LI(li) {}
43
44    LoopInfo &getLoopInfo() const { return LI; }
45
46    /// clear - Erase the contents of the InsertedExpressions map so that users
47    /// trying to expand the same expression into multiple BasicBlocks or
48    /// different places within the same BasicBlock can do so.
49    void clear() { InsertedExpressions.clear(); }
50
51    /// isInsertedInstruction - Return true if the specified instruction was
52    /// inserted by the code rewriter.  If so, the client should not modify the
53    /// instruction.
54    bool isInsertedInstruction(Instruction *I) const {
55      return InsertedInstructions.count(I);
56    }
57
58    /// getOrInsertCanonicalInductionVariable - This method returns the
59    /// canonical induction variable of the specified type for the specified
60    /// loop (inserting one if there is none).  A canonical induction variable
61    /// starts at zero and steps by one on each iteration.
62    Value *getOrInsertCanonicalInductionVariable(const Loop *L, const Type *Ty){
63      assert(Ty->isInteger() && "Can only insert integer induction variables!");
64      SCEVHandle H = SE.getAddRecExpr(SE.getIntegerSCEV(0, Ty),
65                                      SE.getIntegerSCEV(1, Ty), L);
66      return expand(H);
67    }
68
69    /// addInsertedValue - Remember the specified instruction as being the
70    /// canonical form for the specified SCEV.
71    void addInsertedValue(Instruction *I, SCEV *S) {
72      InsertedExpressions[S] = (Value*)I;
73      InsertedInstructions.insert(I);
74    }
75
76    Instruction *getInsertionPoint() const { return InsertPt; }
77
78    /// expandCodeFor - Insert code to directly compute the specified SCEV
79    /// expression into the program.  The inserted code is inserted into the
80    /// specified block.
81    Value *expandCodeFor(SCEVHandle SH, Instruction *IP) {
82      // Expand the code for this SCEV.
83      this->InsertPt = IP;
84      return expand(SH);
85    }
86
87    /// InsertCastOfTo - Insert a cast of V to the specified type, doing what
88    /// we can to share the casts.
89    static Value *InsertCastOfTo(Instruction::CastOps opcode, Value *V,
90                                 const Type *Ty);
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, Instruction *&InsertPt);
95  protected:
96    Value *expand(SCEV *S);
97
98    Value *visitConstant(SCEVConstant *S) {
99      return S->getValue();
100    }
101
102    Value *visitTruncateExpr(SCEVTruncateExpr *S) {
103      Value *V = expand(S->getOperand());
104      return CastInst::createTruncOrBitCast(V, S->getType(), "tmp.", InsertPt);
105    }
106
107    Value *visitZeroExtendExpr(SCEVZeroExtendExpr *S) {
108      Value *V = expand(S->getOperand());
109      return CastInst::createZExtOrBitCast(V, S->getType(), "tmp.", InsertPt);
110    }
111
112    Value *visitSignExtendExpr(SCEVSignExtendExpr *S) {
113      Value *V = expand(S->getOperand());
114      return CastInst::createSExtOrBitCast(V, S->getType(), "tmp.", InsertPt);
115    }
116
117    Value *visitAddExpr(SCEVAddExpr *S) {
118      Value *V = expand(S->getOperand(S->getNumOperands()-1));
119
120      // Emit a bunch of add instructions
121      for (int i = S->getNumOperands()-2; i >= 0; --i)
122        V = InsertBinop(Instruction::Add, V, expand(S->getOperand(i)),
123                        InsertPt);
124      return V;
125    }
126
127    Value *visitMulExpr(SCEVMulExpr *S);
128
129    Value *visitUDivExpr(SCEVUDivExpr *S) {
130      Value *LHS = expand(S->getLHS());
131      Value *RHS = expand(S->getRHS());
132      return InsertBinop(Instruction::UDiv, LHS, RHS, InsertPt);
133    }
134
135    Value *visitAddRecExpr(SCEVAddRecExpr *S);
136
137    Value *visitSMaxExpr(SCEVSMaxExpr *S);
138
139    Value *visitUMaxExpr(SCEVUMaxExpr *S);
140
141    Value *visitUnknown(SCEVUnknown *S) {
142      return S->getValue();
143    }
144  };
145}
146
147#endif
148
149