1 //===---- llvm/Analysis/ScalarEvolutionExpander.h - SCEV Exprs --*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines the classes used to generate code from scalar expressions.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_ANALYSIS_SCALAREVOLUTION_EXPANDER_H
15 #define LLVM_ANALYSIS_SCALAREVOLUTION_EXPANDER_H
17 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
18 #include "llvm/Analysis/ScalarEvolutionNormalization.h"
19 #include "llvm/Support/IRBuilder.h"
20 #include "llvm/Support/TargetFolder.h"
21 #include "llvm/Support/ValueHandle.h"
25 /// SCEVExpander - This class uses information about analyze scalars to
26 /// rewrite expressions in canonical form.
28 /// Clients should create an instance of this class when rewriting is needed,
29 /// and destroy it when finished to allow the release of the associated
31 class SCEVExpander : public SCEVVisitor<SCEVExpander, Value*> {
34 // New instructions receive a name to identifies them with the current pass.
37 std::map<std::pair<const SCEV *, Instruction *>, AssertingVH<Value> >
39 std::set<AssertingVH<Value> > InsertedValues;
40 std::set<AssertingVH<Value> > InsertedPostIncValues;
42 /// RelevantLoops - A memoization of the "relevant" loop for a given SCEV.
43 DenseMap<const SCEV *, const Loop *> RelevantLoops;
45 /// PostIncLoops - Addrecs referring to any of the given loops are expanded
46 /// in post-inc mode. For example, expanding {1,+,1}<L> in post-inc mode
47 /// returns the add instruction that adds one to the phi for {0,+,1}<L>,
48 /// as opposed to a new phi starting at 1. This is only supported in
49 /// non-canonical mode.
50 PostIncLoopSet PostIncLoops;
52 /// IVIncInsertPos - When this is non-null, addrecs expanded in the
53 /// loop it indicates should be inserted with increments at
55 const Loop *IVIncInsertLoop;
57 /// IVIncInsertPos - When expanding addrecs in the IVIncInsertLoop loop,
58 /// insert the IV increment at this position.
59 Instruction *IVIncInsertPos;
61 /// CanonicalMode - When true, expressions are expanded in "canonical"
62 /// form. In particular, addrecs are expanded as arithmetic based on
63 /// a canonical induction variable. When false, expression are expanded
64 /// in a more literal form.
67 /// When invoked from LSR, the expander is in "strength reduction" mode. The
68 /// only difference is that phi's are only reused if they are already in
72 typedef IRBuilder<true, TargetFolder> BuilderType;
75 friend struct SCEVVisitor<SCEVExpander, Value*>;
78 /// SCEVExpander - Construct a SCEVExpander in "canonical" mode.
79 explicit SCEVExpander(ScalarEvolution &se, const char *name)
80 : SE(se), IVName(name), IVIncInsertLoop(0), IVIncInsertPos(0),
81 CanonicalMode(true), LSRMode(false),
82 Builder(se.getContext(), TargetFolder(se.TD)) {}
84 /// clear - Erase the contents of the InsertedExpressions map so that users
85 /// trying to expand the same expression into multiple BasicBlocks or
86 /// different places within the same BasicBlock can do so.
88 InsertedExpressions.clear();
89 InsertedValues.clear();
90 InsertedPostIncValues.clear();
93 /// getOrInsertCanonicalInductionVariable - This method returns the
94 /// canonical induction variable of the specified type for the specified
95 /// loop (inserting one if there is none). A canonical induction variable
96 /// starts at zero and steps by one on each iteration.
97 PHINode *getOrInsertCanonicalInductionVariable(const Loop *L, Type *Ty);
99 /// expandCodeFor - Insert code to directly compute the specified SCEV
100 /// expression into the program. The inserted code is inserted into the
102 Value *expandCodeFor(const SCEV *SH, Type *Ty, Instruction *I);
104 /// setIVIncInsertPos - Set the current IV increment loop and position.
105 void setIVIncInsertPos(const Loop *L, Instruction *Pos) {
106 assert(!CanonicalMode &&
107 "IV increment positions are not supported in CanonicalMode");
109 IVIncInsertPos = Pos;
112 /// setPostInc - Enable post-inc expansion for addrecs referring to the
113 /// given loops. Post-inc expansion is only supported in non-canonical
115 void setPostInc(const PostIncLoopSet &L) {
116 assert(!CanonicalMode &&
117 "Post-inc expansion is not supported in CanonicalMode");
121 /// clearPostInc - Disable all post-inc expansion.
122 void clearPostInc() {
123 PostIncLoops.clear();
125 // When we change the post-inc loop set, cached expansions may no
127 InsertedPostIncValues.clear();
130 /// disableCanonicalMode - Disable the behavior of expanding expressions in
131 /// canonical form rather than in a more literal form. Non-canonical mode
132 /// is useful for late optimization passes.
133 void disableCanonicalMode() { CanonicalMode = false; }
135 void enableLSRMode() { LSRMode = true; }
137 /// clearInsertPoint - Clear the current insertion point. This is useful
138 /// if the instruction that had been serving as the insertion point may
139 /// have been deleted.
140 void clearInsertPoint() {
141 Builder.ClearInsertionPoint();
144 LLVMContext &getContext() const { return SE.getContext(); }
146 /// InsertBinop - Insert the specified binary operator, doing a small amount
147 /// of work to avoid inserting an obviously redundant operation.
148 Value *InsertBinop(Instruction::BinaryOps Opcode, Value *LHS, Value *RHS);
150 /// ReuseOrCreateCast - Arange for there to be a cast of V to Ty at IP,
151 /// reusing an existing cast if a suitable one exists, moving an existing
152 /// cast if a suitable one exists but isn't in the right place, or
153 /// or creating a new one.
154 Value *ReuseOrCreateCast(Value *V, Type *Ty,
155 Instruction::CastOps Op,
156 BasicBlock::iterator IP);
158 /// InsertNoopCastOfTo - Insert a cast of V to the specified type,
159 /// which must be possible with a noop cast, doing what we can to
161 Value *InsertNoopCastOfTo(Value *V, Type *Ty);
163 /// expandAddToGEP - Expand a SCEVAddExpr with a pointer type into a GEP
164 /// instead of using ptrtoint+arithmetic+inttoptr.
165 Value *expandAddToGEP(const SCEV *const *op_begin,
166 const SCEV *const *op_end,
167 PointerType *PTy, Type *Ty, Value *V);
169 Value *expand(const SCEV *S);
171 /// expandCodeFor - Insert code to directly compute the specified SCEV
172 /// expression into the program. The inserted code is inserted into the
173 /// SCEVExpander's current insertion point. If a type is specified, the
174 /// result will be expanded to have that type, with a cast if necessary.
175 Value *expandCodeFor(const SCEV *SH, Type *Ty = 0);
177 /// isInsertedInstruction - Return true if the specified instruction was
178 /// inserted by the code rewriter. If so, the client should not modify the
180 bool isInsertedInstruction(Instruction *I) const {
181 return InsertedValues.count(I) || InsertedPostIncValues.count(I);
184 /// getRelevantLoop - Determine the most "relevant" loop for the given SCEV.
185 const Loop *getRelevantLoop(const SCEV *);
187 Value *visitConstant(const SCEVConstant *S) {
188 return S->getValue();
191 Value *visitTruncateExpr(const SCEVTruncateExpr *S);
193 Value *visitZeroExtendExpr(const SCEVZeroExtendExpr *S);
195 Value *visitSignExtendExpr(const SCEVSignExtendExpr *S);
197 Value *visitAddExpr(const SCEVAddExpr *S);
199 Value *visitMulExpr(const SCEVMulExpr *S);
201 Value *visitUDivExpr(const SCEVUDivExpr *S);
203 Value *visitAddRecExpr(const SCEVAddRecExpr *S);
205 Value *visitSMaxExpr(const SCEVSMaxExpr *S);
207 Value *visitUMaxExpr(const SCEVUMaxExpr *S);
209 Value *visitUnknown(const SCEVUnknown *S) {
210 return S->getValue();
213 void rememberInstruction(Value *I);
215 void restoreInsertPoint(BasicBlock *BB, BasicBlock::iterator I);
217 bool isNormalAddRecExprPHI(PHINode *PN, Instruction *IncV, const Loop *L);
219 bool isExpandedAddRecExprPHI(PHINode *PN, Instruction *IncV, const Loop *L,
222 Value *expandAddRecExprLiterally(const SCEVAddRecExpr *);
223 PHINode *getAddRecExprPHILiterally(const SCEVAddRecExpr *Normalized,