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*> {
40 // New instructions receive a name to identifies them with the current pass.
43 // InsertedExpressions caches Values for reuse, so must track RAUW.
44 std::map<std::pair<const SCEV *, Instruction *>, TrackingVH<Value> >
46 // InsertedValues only flags inserted instructions so needs no RAUW.
47 std::set<AssertingVH<Value> > InsertedValues;
48 std::set<AssertingVH<Value> > InsertedPostIncValues;
50 /// RelevantLoops - A memoization of the "relevant" loop for a given SCEV.
51 DenseMap<const SCEV *, const Loop *> RelevantLoops;
53 /// PostIncLoops - Addrecs referring to any of the given loops are expanded
54 /// in post-inc mode. For example, expanding {1,+,1}<L> in post-inc mode
55 /// returns the add instruction that adds one to the phi for {0,+,1}<L>,
56 /// as opposed to a new phi starting at 1. This is only supported in
57 /// non-canonical mode.
58 PostIncLoopSet PostIncLoops;
60 /// IVIncInsertPos - When this is non-null, addrecs expanded in the
61 /// loop it indicates should be inserted with increments at
63 const Loop *IVIncInsertLoop;
65 /// IVIncInsertPos - When expanding addrecs in the IVIncInsertLoop loop,
66 /// insert the IV increment at this position.
67 Instruction *IVIncInsertPos;
69 /// Phis that complete an IV chain. Reuse
70 std::set<AssertingVH<PHINode> > ChainedPhis;
72 /// CanonicalMode - When true, expressions are expanded in "canonical"
73 /// form. In particular, addrecs are expanded as arithmetic based on
74 /// a canonical induction variable. When false, expression are expanded
75 /// in a more literal form.
78 /// When invoked from LSR, the expander is in "strength reduction" mode. The
79 /// only difference is that phi's are only reused if they are already in
83 typedef IRBuilder<true, TargetFolder> BuilderType;
87 const char *DebugType;
90 friend struct SCEVVisitor<SCEVExpander, Value*>;
93 /// SCEVExpander - Construct a SCEVExpander in "canonical" mode.
94 explicit SCEVExpander(ScalarEvolution &se, const char *name)
95 : SE(se), IVName(name), IVIncInsertLoop(nullptr), IVIncInsertPos(nullptr),
96 CanonicalMode(true), LSRMode(false),
97 Builder(se.getContext(), TargetFolder(se.DL)) {
104 void setDebugType(const char* s) { DebugType = s; }
107 /// clear - Erase the contents of the InsertedExpressions map so that users
108 /// trying to expand the same expression into multiple BasicBlocks or
109 /// different places within the same BasicBlock can do so.
111 InsertedExpressions.clear();
112 InsertedValues.clear();
113 InsertedPostIncValues.clear();
117 /// getOrInsertCanonicalInductionVariable - This method returns the
118 /// canonical induction variable of the specified type for the specified
119 /// loop (inserting one if there is none). A canonical induction variable
120 /// starts at zero and steps by one on each iteration.
121 PHINode *getOrInsertCanonicalInductionVariable(const Loop *L, Type *Ty);
123 /// getIVIncOperand - Return the induction variable increment's IV operand.
124 Instruction *getIVIncOperand(Instruction *IncV, Instruction *InsertPos,
127 /// hoistIVInc - Utility for hoisting an IV increment.
128 bool hoistIVInc(Instruction *IncV, Instruction *InsertPos);
130 /// replaceCongruentIVs - replace congruent phis with their most canonical
131 /// representative. Return the number of phis eliminated.
132 unsigned replaceCongruentIVs(Loop *L, const DominatorTree *DT,
133 SmallVectorImpl<WeakVH> &DeadInsts,
134 const TargetTransformInfo *TTI = nullptr);
136 /// expandCodeFor - Insert code to directly compute the specified SCEV
137 /// expression into the program. The inserted code is inserted into the
139 Value *expandCodeFor(const SCEV *SH, Type *Ty, Instruction *I);
141 /// setIVIncInsertPos - Set the current IV increment loop and position.
142 void setIVIncInsertPos(const Loop *L, Instruction *Pos) {
143 assert(!CanonicalMode &&
144 "IV increment positions are not supported in CanonicalMode");
146 IVIncInsertPos = Pos;
149 /// setPostInc - Enable post-inc expansion for addrecs referring to the
150 /// given loops. Post-inc expansion is only supported in non-canonical
152 void setPostInc(const PostIncLoopSet &L) {
153 assert(!CanonicalMode &&
154 "Post-inc expansion is not supported in CanonicalMode");
158 /// clearPostInc - Disable all post-inc expansion.
159 void clearPostInc() {
160 PostIncLoops.clear();
162 // When we change the post-inc loop set, cached expansions may no
164 InsertedPostIncValues.clear();
167 /// disableCanonicalMode - Disable the behavior of expanding expressions in
168 /// canonical form rather than in a more literal form. Non-canonical mode
169 /// is useful for late optimization passes.
170 void disableCanonicalMode() { CanonicalMode = false; }
172 void enableLSRMode() { LSRMode = true; }
174 /// clearInsertPoint - Clear the current insertion point. This is useful
175 /// if the instruction that had been serving as the insertion point may
176 /// have been deleted.
177 void clearInsertPoint() {
178 Builder.ClearInsertionPoint();
181 /// isInsertedInstruction - Return true if the specified instruction was
182 /// inserted by the code rewriter. If so, the client should not modify the
184 bool isInsertedInstruction(Instruction *I) const {
185 return InsertedValues.count(I) || InsertedPostIncValues.count(I);
188 void setChainedPhi(PHINode *PN) { ChainedPhis.insert(PN); }
191 LLVMContext &getContext() const { return SE.getContext(); }
193 /// InsertBinop - Insert the specified binary operator, doing a small amount
194 /// of work to avoid inserting an obviously redundant operation.
195 Value *InsertBinop(Instruction::BinaryOps Opcode, Value *LHS, Value *RHS);
197 /// ReuseOrCreateCast - Arange for there to be a cast of V to Ty at IP,
198 /// reusing an existing cast if a suitable one exists, moving an existing
199 /// cast if a suitable one exists but isn't in the right place, or
200 /// or creating a new one.
201 Value *ReuseOrCreateCast(Value *V, Type *Ty,
202 Instruction::CastOps Op,
203 BasicBlock::iterator IP);
205 /// InsertNoopCastOfTo - Insert a cast of V to the specified type,
206 /// which must be possible with a noop cast, doing what we can to
208 Value *InsertNoopCastOfTo(Value *V, Type *Ty);
210 /// expandAddToGEP - Expand a SCEVAddExpr with a pointer type into a GEP
211 /// instead of using ptrtoint+arithmetic+inttoptr.
212 Value *expandAddToGEP(const SCEV *const *op_begin,
213 const SCEV *const *op_end,
214 PointerType *PTy, Type *Ty, Value *V);
216 Value *expand(const SCEV *S);
218 /// expandCodeFor - Insert code to directly compute the specified SCEV
219 /// expression into the program. The inserted code is inserted into the
220 /// SCEVExpander's current insertion point. If a type is specified, the
221 /// result will be expanded to have that type, with a cast if necessary.
222 Value *expandCodeFor(const SCEV *SH, Type *Ty = nullptr);
224 /// getRelevantLoop - Determine the most "relevant" loop for the given SCEV.
225 const Loop *getRelevantLoop(const SCEV *);
227 Value *visitConstant(const SCEVConstant *S) {
228 return S->getValue();
231 Value *visitTruncateExpr(const SCEVTruncateExpr *S);
233 Value *visitZeroExtendExpr(const SCEVZeroExtendExpr *S);
235 Value *visitSignExtendExpr(const SCEVSignExtendExpr *S);
237 Value *visitAddExpr(const SCEVAddExpr *S);
239 Value *visitMulExpr(const SCEVMulExpr *S);
241 Value *visitUDivExpr(const SCEVUDivExpr *S);
243 Value *visitAddRecExpr(const SCEVAddRecExpr *S);
245 Value *visitSMaxExpr(const SCEVSMaxExpr *S);
247 Value *visitUMaxExpr(const SCEVUMaxExpr *S);
249 Value *visitUnknown(const SCEVUnknown *S) {
250 return S->getValue();
253 void rememberInstruction(Value *I);
255 bool isNormalAddRecExprPHI(PHINode *PN, Instruction *IncV, const Loop *L);
257 bool isExpandedAddRecExprPHI(PHINode *PN, Instruction *IncV, const Loop *L);
259 Value *expandAddRecExprLiterally(const SCEVAddRecExpr *);
260 PHINode *getAddRecExprPHILiterally(const SCEVAddRecExpr *Normalized,
266 Value *expandIVInc(PHINode *PN, Value *StepV, const Loop *L,
267 Type *ExpandTy, Type *IntTy, bool useSubtract);