1 //===- PredicateInfo.h - Build PredicateInfo ----------------------*-C++-*-===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 /// 10 /// \file 11 /// \brief This file implements the PredicateInfo analysis, which creates an Extended 12 /// SSA form for operations used in branch comparisons and llvm.assume 13 /// comparisons. 14 /// 15 /// Copies of these operations are inserted into the true/false edge (and after 16 /// assumes), and information attached to the copies. All uses of the original 17 /// operation in blocks dominated by the true/false edge (and assume), are 18 /// replaced with uses of the copies. This enables passes to easily and sparsely 19 /// propagate condition based info into the operations that may be affected. 20 /// 21 /// Example: 22 /// %cmp = icmp eq i32 %x, 50 23 /// br i1 %cmp, label %true, label %false 24 /// true: 25 /// ret i32 %x 26 /// false: 27 /// ret i32 1 28 /// 29 /// will become 30 /// 31 /// %cmp = icmp eq i32, %x, 50 32 /// br i1 %cmp, label %true, label %false 33 /// true: 34 /// %x.0 = call @llvm.ssa_copy.i32(i32 %x) 35 /// ret i32 %x.0 36 /// false: 37 /// ret i32 1 38 /// 39 /// Using getPredicateInfoFor on x.0 will give you the comparison it is 40 /// dominated by (the icmp), and that you are located in the true edge of that 41 /// comparison, which tells you x.0 is 50. 42 /// 43 /// In order to reduce the number of copies inserted, predicateinfo is only 44 /// inserted where it would actually be live. This means if there are no uses of 45 /// an operation dominated by the branch edges, or by an assume, the associated 46 /// predicate info is never inserted. 47 /// 48 /// 49 //===----------------------------------------------------------------------===// 50 51 #ifndef LLVM_TRANSFORMS_UTILS_PREDICATEINFO_H 52 #define LLVM_TRANSFORMS_UTILS_PREDICATEINFO_H 53 54 #include "llvm/ADT/DenseMap.h" 55 #include "llvm/ADT/DenseSet.h" 56 #include "llvm/ADT/SmallPtrSet.h" 57 #include "llvm/ADT/SmallVector.h" 58 #include "llvm/ADT/ilist.h" 59 #include "llvm/ADT/ilist_node.h" 60 #include "llvm/ADT/iterator.h" 61 #include "llvm/Analysis/AssumptionCache.h" 62 #include "llvm/IR/BasicBlock.h" 63 #include "llvm/IR/Dominators.h" 64 #include "llvm/IR/Instructions.h" 65 #include "llvm/IR/IntrinsicInst.h" 66 #include "llvm/IR/Module.h" 67 #include "llvm/IR/OperandTraits.h" 68 #include "llvm/IR/Type.h" 69 #include "llvm/IR/Use.h" 70 #include "llvm/IR/User.h" 71 #include "llvm/IR/Value.h" 72 #include "llvm/Pass.h" 73 #include "llvm/PassAnalysisSupport.h" 74 #include "llvm/Support/Casting.h" 75 #include "llvm/Support/Compiler.h" 76 #include "llvm/Support/ErrorHandling.h" 77 #include "llvm/Transforms/Utils/OrderedInstructions.h" 78 #include <algorithm> 79 #include <cassert> 80 #include <cstddef> 81 #include <iterator> 82 #include <memory> 83 #include <utility> 84 85 namespace llvm { 86 87 class DominatorTree; 88 class Function; 89 class Instruction; 90 class MemoryAccess; 91 class LLVMContext; 92 class raw_ostream; 93 94 enum PredicateType { PT_Branch, PT_Assume, PT_Switch }; 95 96 // Base class for all predicate information we provide. 97 // All of our predicate information has at least a comparison. 98 class PredicateBase : public ilist_node<PredicateBase> { 99 public: 100 PredicateType Type; 101 // The original operand before we renamed it. 102 // This can be use by passes, when destroying predicateinfo, to know 103 // whether they can just drop the intrinsic, or have to merge metadata. 104 Value *OriginalOp; 105 PredicateBase(const PredicateBase &) = delete; 106 PredicateBase &operator=(const PredicateBase &) = delete; 107 PredicateBase() = delete; 108 virtual ~PredicateBase() = default; 109 110 protected: 111 PredicateBase(PredicateType PT, Value *Op) : Type(PT), OriginalOp(Op) {} 112 }; 113 114 class PredicateWithCondition : public PredicateBase { 115 public: 116 Value *Condition; 117 static bool classof(const PredicateBase *PB) { 118 return PB->Type == PT_Assume || PB->Type == PT_Branch || 119 PB->Type == PT_Switch; 120 } 121 122 protected: 123 PredicateWithCondition(PredicateType PT, Value *Op, Value *Condition) 124 : PredicateBase(PT, Op), Condition(Condition) {} 125 }; 126 127 // Provides predicate information for assumes. Since assumes are always true, 128 // we simply provide the assume instruction, so you can tell your relative 129 // position to it. 130 class PredicateAssume : public PredicateWithCondition { 131 public: 132 IntrinsicInst *AssumeInst; 133 PredicateAssume(Value *Op, IntrinsicInst *AssumeInst, Value *Condition) 134 : PredicateWithCondition(PT_Assume, Op, Condition), 135 AssumeInst(AssumeInst) {} 136 PredicateAssume() = delete; 137 static bool classof(const PredicateBase *PB) { 138 return PB->Type == PT_Assume; 139 } 140 }; 141 142 // Mixin class for edge predicates. The FROM block is the block where the 143 // predicate originates, and the TO block is the block where the predicate is 144 // valid. 145 class PredicateWithEdge : public PredicateWithCondition { 146 public: 147 BasicBlock *From; 148 BasicBlock *To; 149 PredicateWithEdge() = delete; 150 static bool classof(const PredicateBase *PB) { 151 return PB->Type == PT_Branch || PB->Type == PT_Switch; 152 } 153 154 protected: 155 PredicateWithEdge(PredicateType PType, Value *Op, BasicBlock *From, 156 BasicBlock *To, Value *Cond) 157 : PredicateWithCondition(PType, Op, Cond), From(From), To(To) {} 158 }; 159 160 // Provides predicate information for branches. 161 class PredicateBranch : public PredicateWithEdge { 162 public: 163 // If true, SplitBB is the true successor, otherwise it's the false successor. 164 bool TrueEdge; 165 PredicateBranch(Value *Op, BasicBlock *BranchBB, BasicBlock *SplitBB, 166 Value *Condition, bool TakenEdge) 167 : PredicateWithEdge(PT_Branch, Op, BranchBB, SplitBB, Condition), 168 TrueEdge(TakenEdge) {} 169 PredicateBranch() = delete; 170 static bool classof(const PredicateBase *PB) { 171 return PB->Type == PT_Branch; 172 } 173 }; 174 175 class PredicateSwitch : public PredicateWithEdge { 176 public: 177 Value *CaseValue; 178 // This is the switch instruction. 179 SwitchInst *Switch; 180 PredicateSwitch(Value *Op, BasicBlock *SwitchBB, BasicBlock *TargetBB, 181 Value *CaseValue, SwitchInst *SI) 182 : PredicateWithEdge(PT_Switch, Op, SwitchBB, TargetBB, 183 SI->getCondition()), 184 CaseValue(CaseValue), Switch(SI) {} 185 PredicateSwitch() = delete; 186 static bool classof(const PredicateBase *PB) { 187 return PB->Type == PT_Switch; 188 } 189 }; 190 191 // This name is used in a few places, so kick it into their own namespace 192 namespace PredicateInfoClasses { 193 struct ValueDFS; 194 } 195 196 /// \brief Encapsulates PredicateInfo, including all data associated with memory 197 /// accesses. 198 class PredicateInfo { 199 private: 200 // Used to store information about each value we might rename. 201 struct ValueInfo { 202 // Information about each possible copy. During processing, this is each 203 // inserted info. After processing, we move the uninserted ones to the 204 // uninserted vector. 205 SmallVector<PredicateBase *, 4> Infos; 206 SmallVector<PredicateBase *, 4> UninsertedInfos; 207 }; 208 // This owns the all the predicate infos in the function, placed or not. 209 iplist<PredicateBase> AllInfos; 210 211 public: 212 PredicateInfo(Function &, DominatorTree &, AssumptionCache &); 213 ~PredicateInfo(); 214 215 void verifyPredicateInfo() const; 216 217 void dump() const; 218 void print(raw_ostream &) const; 219 220 const PredicateBase *getPredicateInfoFor(const Value *V) const { 221 return PredicateMap.lookup(V); 222 } 223 224 protected: 225 // Used by PredicateInfo annotater, dumpers, and wrapper pass. 226 friend class PredicateInfoAnnotatedWriter; 227 friend class PredicateInfoPrinterLegacyPass; 228 229 private: 230 void buildPredicateInfo(); 231 void processAssume(IntrinsicInst *, BasicBlock *, SmallPtrSetImpl<Value *> &); 232 void processBranch(BranchInst *, BasicBlock *, SmallPtrSetImpl<Value *> &); 233 void processSwitch(SwitchInst *, BasicBlock *, SmallPtrSetImpl<Value *> &); 234 void renameUses(SmallPtrSetImpl<Value *> &); 235 using ValueDFS = PredicateInfoClasses::ValueDFS; 236 typedef SmallVectorImpl<ValueDFS> ValueDFSStack; 237 void convertUsesToDFSOrdered(Value *, SmallVectorImpl<ValueDFS> &); 238 Value *materializeStack(unsigned int &, ValueDFSStack &, Value *); 239 bool stackIsInScope(const ValueDFSStack &, const ValueDFS &) const; 240 void popStackUntilDFSScope(ValueDFSStack &, const ValueDFS &); 241 ValueInfo &getOrCreateValueInfo(Value *); 242 void addInfoFor(SmallPtrSetImpl<Value *> &OpsToRename, Value *Op, 243 PredicateBase *PB); 244 const ValueInfo &getValueInfo(Value *) const; 245 Function &F; 246 DominatorTree &DT; 247 AssumptionCache &AC; 248 OrderedInstructions OI; 249 // This maps from copy operands to Predicate Info. Note that it does not own 250 // the Predicate Info, they belong to the ValueInfo structs in the ValueInfos 251 // vector. 252 DenseMap<const Value *, const PredicateBase *> PredicateMap; 253 // This stores info about each operand or comparison result we make copies 254 // of. The real ValueInfos start at index 1, index 0 is unused so that we can 255 // more easily detect invalid indexing. 256 SmallVector<ValueInfo, 32> ValueInfos; 257 // This gives the index into the ValueInfos array for a given Value. Because 258 // 0 is not a valid Value Info index, you can use DenseMap::lookup and tell 259 // whether it returned a valid result. 260 DenseMap<Value *, unsigned int> ValueInfoNums; 261 // The set of edges along which we can only handle phi uses, due to critical 262 // edges. 263 DenseSet<std::pair<BasicBlock *, BasicBlock *>> EdgeUsesOnly; 264 }; 265 266 // This pass does eager building and then printing of PredicateInfo. It is used 267 // by 268 // the tests to be able to build, dump, and verify PredicateInfo. 269 class PredicateInfoPrinterLegacyPass : public FunctionPass { 270 public: 271 PredicateInfoPrinterLegacyPass(); 272 273 static char ID; 274 bool runOnFunction(Function &) override; 275 void getAnalysisUsage(AnalysisUsage &AU) const override; 276 }; 277 278 /// \brief Printer pass for \c PredicateInfo. 279 class PredicateInfoPrinterPass 280 : public PassInfoMixin<PredicateInfoPrinterPass> { 281 raw_ostream &OS; 282 283 public: 284 explicit PredicateInfoPrinterPass(raw_ostream &OS) : OS(OS) {} 285 PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM); 286 }; 287 288 /// \brief Verifier pass for \c PredicateInfo. 289 struct PredicateInfoVerifierPass : PassInfoMixin<PredicateInfoVerifierPass> { 290 PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM); 291 }; 292 293 } // end namespace llvm 294 295 #endif // LLVM_TRANSFORMS_UTILS_PREDICATEINFO_H 296