1 //===-- XCoreLowerThreadLocal - Lower thread local variables --------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 /// 9 /// \file 10 /// This file contains a pass that lowers thread local variables on the 11 /// XCore. 12 /// 13 //===----------------------------------------------------------------------===// 14 15 #include "XCore.h" 16 #include "llvm/IR/Constants.h" 17 #include "llvm/IR/DerivedTypes.h" 18 #include "llvm/IR/GlobalVariable.h" 19 #include "llvm/IR/IRBuilder.h" 20 #include "llvm/IR/Intrinsics.h" 21 #include "llvm/IR/IntrinsicsXCore.h" 22 #include "llvm/IR/Module.h" 23 #include "llvm/IR/NoFolder.h" 24 #include "llvm/IR/ValueHandle.h" 25 #include "llvm/Pass.h" 26 #include "llvm/Support/CommandLine.h" 27 #include "llvm/Transforms/Utils/BasicBlockUtils.h" 28 29 #define DEBUG_TYPE "xcore-lower-thread-local" 30 31 using namespace llvm; 32 33 static cl::opt<unsigned> MaxThreads( 34 "xcore-max-threads", cl::Optional, 35 cl::desc("Maximum number of threads (for emulation thread-local storage)"), 36 cl::Hidden, cl::value_desc("number"), cl::init(8)); 37 38 namespace { 39 /// Lowers thread local variables on the XCore. Each thread local variable is 40 /// expanded to an array of n elements indexed by the thread ID where n is the 41 /// fixed number hardware threads supported by the device. 42 struct XCoreLowerThreadLocal : public ModulePass { 43 static char ID; 44 45 XCoreLowerThreadLocal() : ModulePass(ID) { 46 initializeXCoreLowerThreadLocalPass(*PassRegistry::getPassRegistry()); 47 } 48 49 bool lowerGlobal(GlobalVariable *GV); 50 51 bool runOnModule(Module &M) override; 52 }; 53 } 54 55 char XCoreLowerThreadLocal::ID = 0; 56 57 INITIALIZE_PASS(XCoreLowerThreadLocal, "xcore-lower-thread-local", 58 "Lower thread local variables", false, false) 59 60 ModulePass *llvm::createXCoreLowerThreadLocalPass() { 61 return new XCoreLowerThreadLocal(); 62 } 63 64 static ArrayType *createLoweredType(Type *OriginalType) { 65 return ArrayType::get(OriginalType, MaxThreads); 66 } 67 68 static Constant * 69 createLoweredInitializer(ArrayType *NewType, Constant *OriginalInitializer) { 70 SmallVector<Constant *, 8> Elements(MaxThreads); 71 for (unsigned i = 0; i != MaxThreads; ++i) { 72 Elements[i] = OriginalInitializer; 73 } 74 return ConstantArray::get(NewType, Elements); 75 } 76 77 78 static bool replaceConstantExprOp(ConstantExpr *CE, Pass *P) { 79 do { 80 SmallVector<WeakTrackingVH, 8> WUsers(CE->users()); 81 llvm::sort(WUsers); 82 WUsers.erase(std::unique(WUsers.begin(), WUsers.end()), WUsers.end()); 83 while (!WUsers.empty()) 84 if (WeakTrackingVH WU = WUsers.pop_back_val()) { 85 if (PHINode *PN = dyn_cast<PHINode>(WU)) { 86 for (int I = 0, E = PN->getNumIncomingValues(); I < E; ++I) 87 if (PN->getIncomingValue(I) == CE) { 88 BasicBlock *PredBB = PN->getIncomingBlock(I); 89 if (PredBB->getTerminator()->getNumSuccessors() > 1) 90 PredBB = SplitEdge(PredBB, PN->getParent()); 91 Instruction *InsertPos = PredBB->getTerminator(); 92 Instruction *NewInst = CE->getAsInstruction(InsertPos); 93 PN->setOperand(I, NewInst); 94 } 95 } else if (Instruction *Instr = dyn_cast<Instruction>(WU)) { 96 Instruction *NewInst = CE->getAsInstruction(Instr); 97 Instr->replaceUsesOfWith(CE, NewInst); 98 } else { 99 ConstantExpr *CExpr = dyn_cast<ConstantExpr>(WU); 100 if (!CExpr || !replaceConstantExprOp(CExpr, P)) 101 return false; 102 } 103 } 104 } while (CE->hasNUsesOrMore(1)); // We need to check because a recursive 105 // sibling may have used 'CE' when getAsInstruction was called. 106 CE->destroyConstant(); 107 return true; 108 } 109 110 static bool rewriteNonInstructionUses(GlobalVariable *GV, Pass *P) { 111 SmallVector<WeakTrackingVH, 8> WUsers; 112 for (User *U : GV->users()) 113 if (!isa<Instruction>(U)) 114 WUsers.push_back(WeakTrackingVH(U)); 115 while (!WUsers.empty()) 116 if (WeakTrackingVH WU = WUsers.pop_back_val()) { 117 ConstantExpr *CE = dyn_cast<ConstantExpr>(WU); 118 if (!CE || !replaceConstantExprOp(CE, P)) 119 return false; 120 } 121 return true; 122 } 123 124 static bool isZeroLengthArray(Type *Ty) { 125 ArrayType *AT = dyn_cast<ArrayType>(Ty); 126 return AT && (AT->getNumElements() == 0); 127 } 128 129 bool XCoreLowerThreadLocal::lowerGlobal(GlobalVariable *GV) { 130 Module *M = GV->getParent(); 131 if (!GV->isThreadLocal()) 132 return false; 133 134 // Skip globals that we can't lower and leave it for the backend to error. 135 if (!rewriteNonInstructionUses(GV, this) || 136 !GV->getType()->isSized() || isZeroLengthArray(GV->getType())) 137 return false; 138 139 // Create replacement global. 140 ArrayType *NewType = createLoweredType(GV->getValueType()); 141 Constant *NewInitializer = nullptr; 142 if (GV->hasInitializer()) 143 NewInitializer = createLoweredInitializer(NewType, 144 GV->getInitializer()); 145 GlobalVariable *NewGV = 146 new GlobalVariable(*M, NewType, GV->isConstant(), GV->getLinkage(), 147 NewInitializer, "", nullptr, 148 GlobalVariable::NotThreadLocal, 149 GV->getType()->getAddressSpace(), 150 GV->isExternallyInitialized()); 151 152 // Update uses. 153 SmallVector<User *, 16> Users(GV->users()); 154 for (unsigned I = 0, E = Users.size(); I != E; ++I) { 155 User *U = Users[I]; 156 Instruction *Inst = cast<Instruction>(U); 157 IRBuilder<> Builder(Inst); 158 Function *GetID = Intrinsic::getDeclaration(GV->getParent(), 159 Intrinsic::xcore_getid); 160 Value *ThreadID = Builder.CreateCall(GetID, {}); 161 Value *Addr = Builder.CreateInBoundsGEP(NewGV->getValueType(), NewGV, 162 {Builder.getInt64(0), ThreadID}); 163 U->replaceUsesOfWith(GV, Addr); 164 } 165 166 // Remove old global. 167 NewGV->takeName(GV); 168 GV->eraseFromParent(); 169 return true; 170 } 171 172 bool XCoreLowerThreadLocal::runOnModule(Module &M) { 173 // Find thread local globals. 174 bool MadeChange = false; 175 SmallVector<GlobalVariable *, 16> ThreadLocalGlobals; 176 for (GlobalVariable &GV : M.globals()) 177 if (GV.isThreadLocal()) 178 ThreadLocalGlobals.push_back(&GV); 179 for (unsigned I = 0, E = ThreadLocalGlobals.size(); I != E; ++I) { 180 MadeChange |= lowerGlobal(ThreadLocalGlobals[I]); 181 } 182 return MadeChange; 183 } 184