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"
27 /// SCEVExpander - This class uses information about analyze scalars to
28 /// rewrite expressions in canonical form.
30 /// Clients should create an instance of this class when rewriting is needed,
31 /// and destroy it when finished to allow the release of the associated
33 class SCEVExpander : public SCEVVisitor<SCEVExpander, Value*> {
36 // New instructions receive a name to identifies them with the current pass.
39 std::map<std::pair<const SCEV *, Instruction *>, AssertingVH<Value> >
41 std::set<AssertingVH<Value> > InsertedValues;
42 std::set<AssertingVH<Value> > InsertedPostIncValues;
44 /// RelevantLoops - A memoization of the "relevant" loop for a given SCEV.
45 DenseMap<const SCEV *, const Loop *> RelevantLoops;
47 /// PostIncLoops - Addrecs referring to any of the given loops are expanded
48 /// in post-inc mode. For example, expanding {1,+,1}<L> in post-inc mode
49 /// returns the add instruction that adds one to the phi for {0,+,1}<L>,
50 /// as opposed to a new phi starting at 1. This is only supported in
51 /// non-canonical mode.
52 PostIncLoopSet PostIncLoops;
54 /// IVIncInsertPos - When this is non-null, addrecs expanded in the
55 /// loop it indicates should be inserted with increments at
57 const Loop *IVIncInsertLoop;
59 /// IVIncInsertPos - When expanding addrecs in the IVIncInsertLoop loop,
60 /// insert the IV increment at this position.
61 Instruction *IVIncInsertPos;
63 /// CanonicalMode - When true, expressions are expanded in "canonical"
64 /// form. In particular, addrecs are expanded as arithmetic based on
65 /// a canonical induction variable. When false, expression are expanded
66 /// in a more literal form.
69 /// When invoked from LSR, the expander is in "strength reduction" mode. The
70 /// only difference is that phi's are only reused if they are already in
74 typedef IRBuilder<true, TargetFolder> BuilderType;
78 const char *DebugType;
81 friend struct SCEVVisitor<SCEVExpander, Value*>;
84 /// SCEVExpander - Construct a SCEVExpander in "canonical" mode.
85 explicit SCEVExpander(ScalarEvolution &se, const char *name)
86 : SE(se), IVName(name), IVIncInsertLoop(0), IVIncInsertPos(0),
87 CanonicalMode(true), LSRMode(false),
88 Builder(se.getContext(), TargetFolder(se.TD)) {
95 void setDebugType(const char* s) { DebugType = s; }
98 /// clear - Erase the contents of the InsertedExpressions map so that users
99 /// trying to expand the same expression into multiple BasicBlocks or
100 /// different places within the same BasicBlock can do so.
102 InsertedExpressions.clear();
103 InsertedValues.clear();
104 InsertedPostIncValues.clear();
107 /// getOrInsertCanonicalInductionVariable - This method returns the
108 /// canonical induction variable of the specified type for the specified
109 /// loop (inserting one if there is none). A canonical induction variable
110 /// starts at zero and steps by one on each iteration.
111 PHINode *getOrInsertCanonicalInductionVariable(const Loop *L, Type *Ty);
113 /// hoistStep - Utility for hoisting an IV increment.
114 static bool hoistStep(Instruction *IncV, Instruction *InsertPos,
115 const DominatorTree *DT);
117 /// replaceCongruentIVs - replace congruent phis with their most canonical
118 /// representative. Return the number of phis eliminated.
119 unsigned replaceCongruentIVs(Loop *L, const DominatorTree *DT,
120 SmallVectorImpl<WeakVH> &DeadInsts,
121 const TargetLowering *TLI = NULL);
123 /// expandCodeFor - Insert code to directly compute the specified SCEV
124 /// expression into the program. The inserted code is inserted into the
126 Value *expandCodeFor(const SCEV *SH, Type *Ty, Instruction *I);
128 /// setIVIncInsertPos - Set the current IV increment loop and position.
129 void setIVIncInsertPos(const Loop *L, Instruction *Pos) {
130 assert(!CanonicalMode &&
131 "IV increment positions are not supported in CanonicalMode");
133 IVIncInsertPos = Pos;
136 /// setPostInc - Enable post-inc expansion for addrecs referring to the
137 /// given loops. Post-inc expansion is only supported in non-canonical
139 void setPostInc(const PostIncLoopSet &L) {
140 assert(!CanonicalMode &&
141 "Post-inc expansion is not supported in CanonicalMode");
145 /// clearPostInc - Disable all post-inc expansion.
146 void clearPostInc() {
147 PostIncLoops.clear();
149 // When we change the post-inc loop set, cached expansions may no
151 InsertedPostIncValues.clear();
154 /// disableCanonicalMode - Disable the behavior of expanding expressions in
155 /// canonical form rather than in a more literal form. Non-canonical mode
156 /// is useful for late optimization passes.
157 void disableCanonicalMode() { CanonicalMode = false; }
159 void enableLSRMode() { LSRMode = true; }
161 /// clearInsertPoint - Clear the current insertion point. This is useful
162 /// if the instruction that had been serving as the insertion point may
163 /// have been deleted.
164 void clearInsertPoint() {
165 Builder.ClearInsertionPoint();
168 LLVMContext &getContext() const { return SE.getContext(); }
170 /// InsertBinop - Insert the specified binary operator, doing a small amount
171 /// of work to avoid inserting an obviously redundant operation.
172 Value *InsertBinop(Instruction::BinaryOps Opcode, Value *LHS, Value *RHS);
174 /// ReuseOrCreateCast - Arange for there to be a cast of V to Ty at IP,
175 /// reusing an existing cast if a suitable one exists, moving an existing
176 /// cast if a suitable one exists but isn't in the right place, or
177 /// or creating a new one.
178 Value *ReuseOrCreateCast(Value *V, Type *Ty,
179 Instruction::CastOps Op,
180 BasicBlock::iterator IP);
182 /// InsertNoopCastOfTo - Insert a cast of V to the specified type,
183 /// which must be possible with a noop cast, doing what we can to
185 Value *InsertNoopCastOfTo(Value *V, Type *Ty);
187 /// expandAddToGEP - Expand a SCEVAddExpr with a pointer type into a GEP
188 /// instead of using ptrtoint+arithmetic+inttoptr.
189 Value *expandAddToGEP(const SCEV *const *op_begin,
190 const SCEV *const *op_end,
191 PointerType *PTy, Type *Ty, Value *V);
193 Value *expand(const SCEV *S);
195 /// expandCodeFor - Insert code to directly compute the specified SCEV
196 /// expression into the program. The inserted code is inserted into the
197 /// SCEVExpander's current insertion point. If a type is specified, the
198 /// result will be expanded to have that type, with a cast if necessary.
199 Value *expandCodeFor(const SCEV *SH, Type *Ty = 0);
201 /// isInsertedInstruction - Return true if the specified instruction was
202 /// inserted by the code rewriter. If so, the client should not modify the
204 bool isInsertedInstruction(Instruction *I) const {
205 return InsertedValues.count(I) || InsertedPostIncValues.count(I);
208 /// getRelevantLoop - Determine the most "relevant" loop for the given SCEV.
209 const Loop *getRelevantLoop(const SCEV *);
211 Value *visitConstant(const SCEVConstant *S) {
212 return S->getValue();
215 Value *visitTruncateExpr(const SCEVTruncateExpr *S);
217 Value *visitZeroExtendExpr(const SCEVZeroExtendExpr *S);
219 Value *visitSignExtendExpr(const SCEVSignExtendExpr *S);
221 Value *visitAddExpr(const SCEVAddExpr *S);
223 Value *visitMulExpr(const SCEVMulExpr *S);
225 Value *visitUDivExpr(const SCEVUDivExpr *S);
227 Value *visitAddRecExpr(const SCEVAddRecExpr *S);
229 Value *visitSMaxExpr(const SCEVSMaxExpr *S);
231 Value *visitUMaxExpr(const SCEVUMaxExpr *S);
233 Value *visitUnknown(const SCEVUnknown *S) {
234 return S->getValue();
237 void rememberInstruction(Value *I);
239 void restoreInsertPoint(BasicBlock *BB, BasicBlock::iterator I);
241 bool isNormalAddRecExprPHI(PHINode *PN, Instruction *IncV, const Loop *L);
243 bool isExpandedAddRecExprPHI(PHINode *PN, Instruction *IncV, const Loop *L);
245 Value *expandAddRecExprLiterally(const SCEVAddRecExpr *);
246 PHINode *getAddRecExprPHILiterally(const SCEVAddRecExpr *Normalized,
250 Value *expandIVInc(PHINode *PN, Value *StepV, const Loop *L,
251 Type *ExpandTy, Type *IntTy, bool useSubtract);