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(llvm::unique(WUsers), 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 BasicBlock::iterator InsertPos = 92 PredBB->getTerminator()->getIterator(); 93 Instruction *NewInst = CE->getAsInstruction(); 94 NewInst->insertBefore(*PredBB, InsertPos); 95 PN->setOperand(I, NewInst); 96 } 97 } else if (Instruction *Instr = dyn_cast<Instruction>(WU)) { 98 Instruction *NewInst = CE->getAsInstruction(); 99 NewInst->insertBefore(*Instr->getParent(), Instr->getIterator()); 100 Instr->replaceUsesOfWith(CE, NewInst); 101 } else { 102 ConstantExpr *CExpr = dyn_cast<ConstantExpr>(WU); 103 if (!CExpr || !replaceConstantExprOp(CExpr, P)) 104 return false; 105 } 106 } 107 } while (CE->hasNUsesOrMore(1)); // We need to check because a recursive 108 // sibling may have used 'CE' when getAsInstruction was called. 109 CE->destroyConstant(); 110 return true; 111 } 112 113 static bool rewriteNonInstructionUses(GlobalVariable *GV, Pass *P) { 114 SmallVector<WeakTrackingVH, 8> WUsers; 115 for (User *U : GV->users()) 116 if (!isa<Instruction>(U)) 117 WUsers.push_back(WeakTrackingVH(U)); 118 while (!WUsers.empty()) 119 if (WeakTrackingVH WU = WUsers.pop_back_val()) { 120 ConstantExpr *CE = dyn_cast<ConstantExpr>(WU); 121 if (!CE || !replaceConstantExprOp(CE, P)) 122 return false; 123 } 124 return true; 125 } 126 127 static bool isZeroLengthArray(Type *Ty) { 128 ArrayType *AT = dyn_cast<ArrayType>(Ty); 129 return AT && (AT->getNumElements() == 0); 130 } 131 132 bool XCoreLowerThreadLocal::lowerGlobal(GlobalVariable *GV) { 133 Module *M = GV->getParent(); 134 if (!GV->isThreadLocal()) 135 return false; 136 137 // Skip globals that we can't lower and leave it for the backend to error. 138 if (!rewriteNonInstructionUses(GV, this) || 139 !GV->getType()->isSized() || isZeroLengthArray(GV->getType())) 140 return false; 141 142 // Create replacement global. 143 ArrayType *NewType = createLoweredType(GV->getValueType()); 144 Constant *NewInitializer = nullptr; 145 if (GV->hasInitializer()) 146 NewInitializer = createLoweredInitializer(NewType, 147 GV->getInitializer()); 148 GlobalVariable *NewGV = 149 new GlobalVariable(*M, NewType, GV->isConstant(), GV->getLinkage(), 150 NewInitializer, "", nullptr, 151 GlobalVariable::NotThreadLocal, 152 GV->getType()->getAddressSpace(), 153 GV->isExternallyInitialized()); 154 155 // Update uses. 156 SmallVector<User *, 16> Users(GV->users()); 157 for (User *U : Users) { 158 Instruction *Inst = cast<Instruction>(U); 159 IRBuilder<> Builder(Inst); 160 Function *GetID = Intrinsic::getDeclaration(GV->getParent(), 161 Intrinsic::xcore_getid); 162 Value *ThreadID = Builder.CreateCall(GetID, {}); 163 Value *Addr = Builder.CreateInBoundsGEP(NewGV->getValueType(), NewGV, 164 {Builder.getInt64(0), ThreadID}); 165 U->replaceUsesOfWith(GV, Addr); 166 } 167 168 // Remove old global. 169 NewGV->takeName(GV); 170 GV->eraseFromParent(); 171 return true; 172 } 173 174 bool XCoreLowerThreadLocal::runOnModule(Module &M) { 175 // Find thread local globals. 176 bool MadeChange = false; 177 SmallVector<GlobalVariable *, 16> ThreadLocalGlobals; 178 for (GlobalVariable &GV : M.globals()) 179 if (GV.isThreadLocal()) 180 ThreadLocalGlobals.push_back(&GV); 181 for (GlobalVariable *GV : ThreadLocalGlobals) 182 MadeChange |= lowerGlobal(GV); 183 return MadeChange; 184 } 185