1 //===-- SIAnnotateControlFlow.cpp - ------------------===// 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 /// Annotates the control flow with hardware specific intrinsics. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #include "AMDGPU.h" 16 #include "llvm/ADT/DepthFirstIterator.h" 17 #include "llvm/Analysis/Dominators.h" 18 #include "llvm/IR/Constants.h" 19 #include "llvm/IR/Instructions.h" 20 #include "llvm/IR/Module.h" 21 #include "llvm/Pass.h" 22 #include "llvm/Transforms/Utils/BasicBlockUtils.h" 23 #include "llvm/Transforms/Utils/SSAUpdater.h" 24 25 using namespace llvm; 26 27 namespace { 28 29 // Complex types used in this pass 30 typedef std::pair<BasicBlock *, Value *> StackEntry; 31 typedef SmallVector<StackEntry, 16> StackVector; 32 33 // Intrinsic names the control flow is annotated with 34 static const char *const IfIntrinsic = "llvm.SI.if"; 35 static const char *const ElseIntrinsic = "llvm.SI.else"; 36 static const char *const BreakIntrinsic = "llvm.SI.break"; 37 static const char *const IfBreakIntrinsic = "llvm.SI.if.break"; 38 static const char *const ElseBreakIntrinsic = "llvm.SI.else.break"; 39 static const char *const LoopIntrinsic = "llvm.SI.loop"; 40 static const char *const EndCfIntrinsic = "llvm.SI.end.cf"; 41 42 class SIAnnotateControlFlow : public FunctionPass { 43 44 static char ID; 45 46 Type *Boolean; 47 Type *Void; 48 Type *Int64; 49 Type *ReturnStruct; 50 51 ConstantInt *BoolTrue; 52 ConstantInt *BoolFalse; 53 UndefValue *BoolUndef; 54 Constant *Int64Zero; 55 56 Constant *If; 57 Constant *Else; 58 Constant *Break; 59 Constant *IfBreak; 60 Constant *ElseBreak; 61 Constant *Loop; 62 Constant *EndCf; 63 64 DominatorTree *DT; 65 StackVector Stack; 66 SSAUpdater PhiInserter; 67 68 bool isTopOfStack(BasicBlock *BB); 69 70 Value *popSaved(); 71 72 void push(BasicBlock *BB, Value *Saved); 73 74 bool isElse(PHINode *Phi); 75 76 void eraseIfUnused(PHINode *Phi); 77 78 void openIf(BranchInst *Term); 79 80 void insertElse(BranchInst *Term); 81 82 void handleLoopCondition(Value *Cond); 83 84 void handleLoop(BranchInst *Term); 85 86 void closeControlFlow(BasicBlock *BB); 87 88 public: 89 SIAnnotateControlFlow(): 90 FunctionPass(ID) { } 91 92 virtual bool doInitialization(Module &M); 93 94 virtual bool runOnFunction(Function &F); 95 96 virtual const char *getPassName() const { 97 return "SI annotate control flow"; 98 } 99 100 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 101 AU.addRequired<DominatorTree>(); 102 AU.addPreserved<DominatorTree>(); 103 FunctionPass::getAnalysisUsage(AU); 104 } 105 106 }; 107 108 } // end anonymous namespace 109 110 char SIAnnotateControlFlow::ID = 0; 111 112 /// \brief Initialize all the types and constants used in the pass 113 bool SIAnnotateControlFlow::doInitialization(Module &M) { 114 LLVMContext &Context = M.getContext(); 115 116 Void = Type::getVoidTy(Context); 117 Boolean = Type::getInt1Ty(Context); 118 Int64 = Type::getInt64Ty(Context); 119 ReturnStruct = StructType::get(Boolean, Int64, (Type *)0); 120 121 BoolTrue = ConstantInt::getTrue(Context); 122 BoolFalse = ConstantInt::getFalse(Context); 123 BoolUndef = UndefValue::get(Boolean); 124 Int64Zero = ConstantInt::get(Int64, 0); 125 126 If = M.getOrInsertFunction( 127 IfIntrinsic, ReturnStruct, Boolean, (Type *)0); 128 129 Else = M.getOrInsertFunction( 130 ElseIntrinsic, ReturnStruct, Int64, (Type *)0); 131 132 Break = M.getOrInsertFunction( 133 BreakIntrinsic, Int64, Int64, (Type *)0); 134 135 IfBreak = M.getOrInsertFunction( 136 IfBreakIntrinsic, Int64, Boolean, Int64, (Type *)0); 137 138 ElseBreak = M.getOrInsertFunction( 139 ElseBreakIntrinsic, Int64, Int64, Int64, (Type *)0); 140 141 Loop = M.getOrInsertFunction( 142 LoopIntrinsic, Boolean, Int64, (Type *)0); 143 144 EndCf = M.getOrInsertFunction( 145 EndCfIntrinsic, Void, Int64, (Type *)0); 146 147 return false; 148 } 149 150 /// \brief Is BB the last block saved on the stack ? 151 bool SIAnnotateControlFlow::isTopOfStack(BasicBlock *BB) { 152 return !Stack.empty() && Stack.back().first == BB; 153 } 154 155 /// \brief Pop the last saved value from the control flow stack 156 Value *SIAnnotateControlFlow::popSaved() { 157 return Stack.pop_back_val().second; 158 } 159 160 /// \brief Push a BB and saved value to the control flow stack 161 void SIAnnotateControlFlow::push(BasicBlock *BB, Value *Saved) { 162 Stack.push_back(std::make_pair(BB, Saved)); 163 } 164 165 /// \brief Can the condition represented by this PHI node treated like 166 /// an "Else" block? 167 bool SIAnnotateControlFlow::isElse(PHINode *Phi) { 168 BasicBlock *IDom = DT->getNode(Phi->getParent())->getIDom()->getBlock(); 169 for (unsigned i = 0, e = Phi->getNumIncomingValues(); i != e; ++i) { 170 if (Phi->getIncomingBlock(i) == IDom) { 171 172 if (Phi->getIncomingValue(i) != BoolTrue) 173 return false; 174 175 } else { 176 if (Phi->getIncomingValue(i) != BoolFalse) 177 return false; 178 179 } 180 } 181 return true; 182 } 183 184 // \brief Erase "Phi" if it is not used any more 185 void SIAnnotateControlFlow::eraseIfUnused(PHINode *Phi) { 186 if (!Phi->hasNUsesOrMore(1)) 187 Phi->eraseFromParent(); 188 } 189 190 /// \brief Open a new "If" block 191 void SIAnnotateControlFlow::openIf(BranchInst *Term) { 192 Value *Ret = CallInst::Create(If, Term->getCondition(), "", Term); 193 Term->setCondition(ExtractValueInst::Create(Ret, 0, "", Term)); 194 push(Term->getSuccessor(1), ExtractValueInst::Create(Ret, 1, "", Term)); 195 } 196 197 /// \brief Close the last "If" block and open a new "Else" block 198 void SIAnnotateControlFlow::insertElse(BranchInst *Term) { 199 Value *Ret = CallInst::Create(Else, popSaved(), "", Term); 200 Term->setCondition(ExtractValueInst::Create(Ret, 0, "", Term)); 201 push(Term->getSuccessor(1), ExtractValueInst::Create(Ret, 1, "", Term)); 202 } 203 204 /// \brief Recursively handle the condition leading to a loop 205 void SIAnnotateControlFlow::handleLoopCondition(Value *Cond) { 206 if (PHINode *Phi = dyn_cast<PHINode>(Cond)) { 207 208 // Handle all non constant incoming values first 209 for (unsigned i = 0, e = Phi->getNumIncomingValues(); i != e; ++i) { 210 Value *Incoming = Phi->getIncomingValue(i); 211 if (isa<ConstantInt>(Incoming)) 212 continue; 213 214 Phi->setIncomingValue(i, BoolFalse); 215 handleLoopCondition(Incoming); 216 } 217 218 BasicBlock *Parent = Phi->getParent(); 219 BasicBlock *IDom = DT->getNode(Parent)->getIDom()->getBlock(); 220 221 for (unsigned i = 0, e = Phi->getNumIncomingValues(); i != e; ++i) { 222 223 Value *Incoming = Phi->getIncomingValue(i); 224 if (Incoming != BoolTrue) 225 continue; 226 227 BasicBlock *From = Phi->getIncomingBlock(i); 228 if (From == IDom) { 229 CallInst *OldEnd = dyn_cast<CallInst>(Parent->getFirstInsertionPt()); 230 if (OldEnd && OldEnd->getCalledFunction() == EndCf) { 231 Value *Args[] = { 232 OldEnd->getArgOperand(0), 233 PhiInserter.GetValueAtEndOfBlock(Parent) 234 }; 235 Value *Ret = CallInst::Create(ElseBreak, Args, "", OldEnd); 236 PhiInserter.AddAvailableValue(Parent, Ret); 237 continue; 238 } 239 } 240 241 TerminatorInst *Insert = From->getTerminator(); 242 Value *Arg = PhiInserter.GetValueAtEndOfBlock(From); 243 Value *Ret = CallInst::Create(Break, Arg, "", Insert); 244 PhiInserter.AddAvailableValue(From, Ret); 245 } 246 eraseIfUnused(Phi); 247 248 } else if (Instruction *Inst = dyn_cast<Instruction>(Cond)) { 249 BasicBlock *Parent = Inst->getParent(); 250 TerminatorInst *Insert = Parent->getTerminator(); 251 Value *Args[] = { Cond, PhiInserter.GetValueAtEndOfBlock(Parent) }; 252 Value *Ret = CallInst::Create(IfBreak, Args, "", Insert); 253 PhiInserter.AddAvailableValue(Parent, Ret); 254 255 } else { 256 assert(0 && "Unhandled loop condition!"); 257 } 258 } 259 260 /// \brief Handle a back edge (loop) 261 void SIAnnotateControlFlow::handleLoop(BranchInst *Term) { 262 BasicBlock *Target = Term->getSuccessor(1); 263 PHINode *Broken = PHINode::Create(Int64, 0, "", &Target->front()); 264 265 PhiInserter.Initialize(Int64, ""); 266 PhiInserter.AddAvailableValue(Target, Broken); 267 268 Value *Cond = Term->getCondition(); 269 Term->setCondition(BoolTrue); 270 handleLoopCondition(Cond); 271 272 BasicBlock *BB = Term->getParent(); 273 Value *Arg = PhiInserter.GetValueAtEndOfBlock(BB); 274 for (pred_iterator PI = pred_begin(Target), PE = pred_end(Target); 275 PI != PE; ++PI) { 276 277 Broken->addIncoming(*PI == BB ? Arg : Int64Zero, *PI); 278 } 279 280 Term->setCondition(CallInst::Create(Loop, Arg, "", Term)); 281 push(Term->getSuccessor(0), Arg); 282 } 283 284 /// \brief Close the last opened control flow 285 void SIAnnotateControlFlow::closeControlFlow(BasicBlock *BB) { 286 CallInst::Create(EndCf, popSaved(), "", BB->getFirstInsertionPt()); 287 } 288 289 /// \brief Annotate the control flow with intrinsics so the backend can 290 /// recognize if/then/else and loops. 291 bool SIAnnotateControlFlow::runOnFunction(Function &F) { 292 DT = &getAnalysis<DominatorTree>(); 293 294 for (df_iterator<BasicBlock *> I = df_begin(&F.getEntryBlock()), 295 E = df_end(&F.getEntryBlock()); I != E; ++I) { 296 297 BranchInst *Term = dyn_cast<BranchInst>((*I)->getTerminator()); 298 299 if (!Term || Term->isUnconditional()) { 300 if (isTopOfStack(*I)) 301 closeControlFlow(*I); 302 continue; 303 } 304 305 if (I.nodeVisited(Term->getSuccessor(1))) { 306 if (isTopOfStack(*I)) 307 closeControlFlow(*I); 308 handleLoop(Term); 309 continue; 310 } 311 312 if (isTopOfStack(*I)) { 313 PHINode *Phi = dyn_cast<PHINode>(Term->getCondition()); 314 if (Phi && Phi->getParent() == *I && isElse(Phi)) { 315 insertElse(Term); 316 eraseIfUnused(Phi); 317 continue; 318 } 319 closeControlFlow(*I); 320 } 321 openIf(Term); 322 } 323 324 assert(Stack.empty()); 325 return true; 326 } 327 328 /// \brief Create the annotation pass 329 FunctionPass *llvm::createSIAnnotateControlFlowPass() { 330 return new SIAnnotateControlFlow(); 331 } 332
