ScalarEvolutionExpander.h revision 24d6da5fedcf39891f7d8c5b031c01324b3db545 
1//===---- llvm/Analysis/ScalarEvolutionExpander.h - SCEV Exprs --*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file was developed by the LLVM research group and is distributed under
6// the University of Illinois Open Source 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 = SCEVAddRecExpr::get(SCEVUnknown::getIntegerSCEV(0, Ty),
65                                         SCEVUnknown::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    /// 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    ///
80    /// If a particular value sign is required, a type may be specified for the
81    /// result.
82    Value *expandCodeFor(SCEVHandle SH, Instruction *IP, const Type *Ty = 0) {
83      // Expand the code for this SCEV.
84      this->InsertPt = IP;
85      return expandInTy(SH, Ty);
86    }
87
88    /// InsertCastOfTo - Insert a cast of V to the specified type, doing what
89    /// we can to share the casts.
90    static Value *InsertCastOfTo(Instruction::CastOps opcode, Value *V,
91                                 const Type *Ty);
92
93  protected:
94    Value *expand(SCEV *S) {
95      // Check to see if we already expanded this.
96      std::map<SCEVHandle, Value*>::iterator I = InsertedExpressions.find(S);
97      if (I != InsertedExpressions.end())
98        return I->second;
99
100      Value *V = visit(S);
101      InsertedExpressions[S] = V;
102      return V;
103    }
104
105    Value *expandInTy(SCEV *S, const Type *Ty) {
106      Value *V = expand(S);
107      if (Ty && V->getType() != Ty) {
108        if (isa<PointerType>(Ty) && V->getType()->isInteger())
109          return InsertCastOfTo(Instruction::IntToPtr, V, Ty);
110        else if (Ty->isInteger() && isa<PointerType>(V->getType()))
111          return InsertCastOfTo(Instruction::PtrToInt, V, Ty);
112        else if (Ty->getPrimitiveSizeInBits() ==
113                 V->getType()->getPrimitiveSizeInBits())
114          return InsertCastOfTo(Instruction::BitCast, V, Ty);
115        else if (Ty->getPrimitiveSizeInBits() >
116                 V->getType()->getPrimitiveSizeInBits())
117          return InsertCastOfTo(Instruction::ZExt, V, Ty);
118        else
119          return InsertCastOfTo(Instruction::Trunc, V, Ty);
120      }
121      return V;
122    }
123
124    Value *visitConstant(SCEVConstant *S) {
125      return S->getValue();
126    }
127
128    Value *visitTruncateExpr(SCEVTruncateExpr *S) {
129      Value *V = expand(S->getOperand());
130      return CastInst::createTruncOrBitCast(V, S->getType(), "tmp.", InsertPt);
131    }
132
133    Value *visitZeroExtendExpr(SCEVZeroExtendExpr *S) {
134      Value *V = expandInTy(S->getOperand(), S->getType());
135      return CastInst::createZExtOrBitCast(V, S->getType(), "tmp.", InsertPt);
136    }
137
138    Value *visitAddExpr(SCEVAddExpr *S) {
139      const Type *Ty = S->getType();
140      Value *V = expandInTy(S->getOperand(S->getNumOperands()-1), Ty);
141
142      // Emit a bunch of add instructions
143      for (int i = S->getNumOperands()-2; i >= 0; --i)
144        V = BinaryOperator::createAdd(V, expandInTy(S->getOperand(i), Ty),
145                                      "tmp.", InsertPt);
146      return V;
147    }
148
149    Value *visitMulExpr(SCEVMulExpr *S);
150
151    Value *visitSDivExpr(SCEVSDivExpr *S) {
152      const Type *Ty = S->getType();
153      Value *LHS = expandInTy(S->getLHS(), Ty);
154      Value *RHS = expandInTy(S->getRHS(), Ty);
155      return BinaryOperator::createSDiv(LHS, RHS, "tmp.", InsertPt);
156    }
157
158    Value *visitAddRecExpr(SCEVAddRecExpr *S);
159
160    Value *visitUnknown(SCEVUnknown *S) {
161      return S->getValue();
162    }
163  };
164}
165
166#endif
167
168