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_SCALAREVOLUTIONEXPANDER_H
15 #define LLVM_ANALYSIS_SCALAREVOLUTIONEXPANDER_H
17 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
18 #include "llvm/Analysis/ScalarEvolutionNormalization.h"
19 #include "llvm/Analysis/TargetFolder.h"
20 #include "llvm/IR/IRBuilder.h"
21 #include "llvm/IR/ValueHandle.h"
25 class TargetTransformInfo;
27 /// Return true if the given expression is safe to expand in the sense that
28 /// all materialized values are safe to speculate.
29 bool isSafeToExpand(const SCEV *S, ScalarEvolution &SE);
31 /// SCEVExpander - This class uses information about analyze scalars to
32 /// rewrite expressions in canonical form.
34 /// Clients should create an instance of this class when rewriting is needed,
35 /// and destroy it when finished to allow the release of the associated
37 class SCEVExpander : public SCEVVisitor<SCEVExpander, Value*> {
41 // New instructions receive a name to identifies them with the current pass.
44 // InsertedExpressions caches Values for reuse, so must track RAUW.
45 std::map<std::pair<const SCEV *, Instruction *>, TrackingVH<Value> >
47 // InsertedValues only flags inserted instructions so needs no RAUW.
48 std::set<AssertingVH<Value> > InsertedValues;
49 std::set<AssertingVH<Value> > InsertedPostIncValues;
51 /// RelevantLoops - A memoization of the "relevant" loop for a given SCEV.
52 DenseMap<const SCEV *, const Loop *> RelevantLoops;
54 /// PostIncLoops - Addrecs referring to any of the given loops are expanded
55 /// in post-inc mode. For example, expanding {1,+,1}<L> in post-inc mode
56 /// returns the add instruction that adds one to the phi for {0,+,1}<L>,
57 /// as opposed to a new phi starting at 1. This is only supported in
58 /// non-canonical mode.
59 PostIncLoopSet PostIncLoops;
61 /// IVIncInsertPos - When this is non-null, addrecs expanded in the
62 /// loop it indicates should be inserted with increments at
64 const Loop *IVIncInsertLoop;
66 /// IVIncInsertPos - When expanding addrecs in the IVIncInsertLoop loop,
67 /// insert the IV increment at this position.
68 Instruction *IVIncInsertPos;
70 /// Phis that complete an IV chain. Reuse
71 std::set<AssertingVH<PHINode> > ChainedPhis;
73 /// CanonicalMode - When true, expressions are expanded in "canonical"
74 /// form. In particular, addrecs are expanded as arithmetic based on
75 /// a canonical induction variable. When false, expression are expanded
76 /// in a more literal form.
79 /// When invoked from LSR, the expander is in "strength reduction" mode. The
80 /// only difference is that phi's are only reused if they are already in
84 typedef IRBuilder<true, TargetFolder> BuilderType;
88 const char *DebugType;
91 friend struct SCEVVisitor<SCEVExpander, Value*>;
94 /// SCEVExpander - Construct a SCEVExpander in "canonical" mode.
95 explicit SCEVExpander(ScalarEvolution &se, const DataLayout &DL,
97 : SE(se), DL(DL), IVName(name), IVIncInsertLoop(nullptr),
98 IVIncInsertPos(nullptr), CanonicalMode(true), LSRMode(false),
99 Builder(se.getContext(), TargetFolder(DL)) {
106 void setDebugType(const char* s) { DebugType = s; }
109 /// clear - Erase the contents of the InsertedExpressions map so that users
110 /// trying to expand the same expression into multiple BasicBlocks or
111 /// different places within the same BasicBlock can do so.
113 InsertedExpressions.clear();
114 InsertedValues.clear();
115 InsertedPostIncValues.clear();
119 /// getOrInsertCanonicalInductionVariable - This method returns the
120 /// canonical induction variable of the specified type for the specified
121 /// loop (inserting one if there is none). A canonical induction variable
122 /// starts at zero and steps by one on each iteration.
123 PHINode *getOrInsertCanonicalInductionVariable(const Loop *L, Type *Ty);
125 /// getIVIncOperand - Return the induction variable increment's IV operand.
126 Instruction *getIVIncOperand(Instruction *IncV, Instruction *InsertPos,
129 /// hoistIVInc - Utility for hoisting an IV increment.
130 bool hoistIVInc(Instruction *IncV, Instruction *InsertPos);
132 /// replaceCongruentIVs - replace congruent phis with their most canonical
133 /// representative. Return the number of phis eliminated.
134 unsigned replaceCongruentIVs(Loop *L, const DominatorTree *DT,
135 SmallVectorImpl<WeakVH> &DeadInsts,
136 const TargetTransformInfo *TTI = nullptr);
138 /// expandCodeFor - Insert code to directly compute the specified SCEV
139 /// expression into the program. The inserted code is inserted into the
141 Value *expandCodeFor(const SCEV *SH, Type *Ty, Instruction *I);
143 /// setIVIncInsertPos - Set the current IV increment loop and position.
144 void setIVIncInsertPos(const Loop *L, Instruction *Pos) {
145 assert(!CanonicalMode &&
146 "IV increment positions are not supported in CanonicalMode");
148 IVIncInsertPos = Pos;
151 /// setPostInc - Enable post-inc expansion for addrecs referring to the
152 /// given loops. Post-inc expansion is only supported in non-canonical
154 void setPostInc(const PostIncLoopSet &L) {
155 assert(!CanonicalMode &&
156 "Post-inc expansion is not supported in CanonicalMode");
160 /// clearPostInc - Disable all post-inc expansion.
161 void clearPostInc() {
162 PostIncLoops.clear();
164 // When we change the post-inc loop set, cached expansions may no
166 InsertedPostIncValues.clear();
169 /// disableCanonicalMode - Disable the behavior of expanding expressions in
170 /// canonical form rather than in a more literal form. Non-canonical mode
171 /// is useful for late optimization passes.
172 void disableCanonicalMode() { CanonicalMode = false; }
174 void enableLSRMode() { LSRMode = true; }
176 /// clearInsertPoint - Clear the current insertion point. This is useful
177 /// if the instruction that had been serving as the insertion point may
178 /// have been deleted.
179 void clearInsertPoint() {
180 Builder.ClearInsertionPoint();
183 /// isInsertedInstruction - Return true if the specified instruction was
184 /// inserted by the code rewriter. If so, the client should not modify the
186 bool isInsertedInstruction(Instruction *I) const {
187 return InsertedValues.count(I) || InsertedPostIncValues.count(I);
190 void setChainedPhi(PHINode *PN) { ChainedPhis.insert(PN); }
193 LLVMContext &getContext() const { return SE.getContext(); }
195 /// InsertBinop - Insert the specified binary operator, doing a small amount
196 /// of work to avoid inserting an obviously redundant operation.
197 Value *InsertBinop(Instruction::BinaryOps Opcode, Value *LHS, Value *RHS);
199 /// ReuseOrCreateCast - Arange for there to be a cast of V to Ty at IP,
200 /// reusing an existing cast if a suitable one exists, moving an existing
201 /// cast if a suitable one exists but isn't in the right place, or
202 /// or creating a new one.
203 Value *ReuseOrCreateCast(Value *V, Type *Ty,
204 Instruction::CastOps Op,
205 BasicBlock::iterator IP);
207 /// InsertNoopCastOfTo - Insert a cast of V to the specified type,
208 /// which must be possible with a noop cast, doing what we can to
210 Value *InsertNoopCastOfTo(Value *V, Type *Ty);
212 /// expandAddToGEP - Expand a SCEVAddExpr with a pointer type into a GEP
213 /// instead of using ptrtoint+arithmetic+inttoptr.
214 Value *expandAddToGEP(const SCEV *const *op_begin,
215 const SCEV *const *op_end,
216 PointerType *PTy, Type *Ty, Value *V);
218 Value *expand(const SCEV *S);
220 /// expandCodeFor - Insert code to directly compute the specified SCEV
221 /// expression into the program. The inserted code is inserted into the
222 /// SCEVExpander's current insertion point. If a type is specified, the
223 /// result will be expanded to have that type, with a cast if necessary.
224 Value *expandCodeFor(const SCEV *SH, Type *Ty = nullptr);
226 /// getRelevantLoop - Determine the most "relevant" loop for the given SCEV.
227 const Loop *getRelevantLoop(const SCEV *);
229 Value *visitConstant(const SCEVConstant *S) {
230 return S->getValue();
233 Value *visitTruncateExpr(const SCEVTruncateExpr *S);
235 Value *visitZeroExtendExpr(const SCEVZeroExtendExpr *S);
237 Value *visitSignExtendExpr(const SCEVSignExtendExpr *S);
239 Value *visitAddExpr(const SCEVAddExpr *S);
241 Value *visitMulExpr(const SCEVMulExpr *S);
243 Value *visitUDivExpr(const SCEVUDivExpr *S);
245 Value *visitAddRecExpr(const SCEVAddRecExpr *S);
247 Value *visitSMaxExpr(const SCEVSMaxExpr *S);
249 Value *visitUMaxExpr(const SCEVUMaxExpr *S);
251 Value *visitUnknown(const SCEVUnknown *S) {
252 return S->getValue();
255 void rememberInstruction(Value *I);
257 bool isNormalAddRecExprPHI(PHINode *PN, Instruction *IncV, const Loop *L);
259 bool isExpandedAddRecExprPHI(PHINode *PN, Instruction *IncV, const Loop *L);
261 Value *expandAddRecExprLiterally(const SCEVAddRecExpr *);
262 PHINode *getAddRecExprPHILiterally(const SCEVAddRecExpr *Normalized,
268 Value *expandIVInc(PHINode *PN, Value *StepV, const Loop *L,
269 Type *ExpandTy, Type *IntTy, bool useSubtract);