lib/Target/XCore/XCoreLowerThreadLocal.cpp

   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/Module.h"
  22 #include "llvm/IR/NoFolder.h"
  23 #include "llvm/IR/ValueHandle.h"
  24 #include "llvm/Pass.h"
  25 #include "llvm/Support/CommandLine.h"
  26 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
  27
  28 #define DEBUG_TYPE "xcore-lower-thread-local"
  29
  30 using namespace llvm;
  31
  32 static cl::opt<unsigned> MaxThreads(
  33   "xcore-max-threads", cl::Optional,
  34   cl::desc("Maximum number of threads (for emulation thread-local storage)"),
  35   cl::Hidden, cl::value_desc("number"), cl::init(8));
  36
  37 namespace {
  38   /// Lowers thread local variables on the XCore. Each thread local variable is
  39   /// expanded to an array of n elements indexed by the thread ID where n is the
  40   /// fixed number hardware threads supported by the device.
  41   struct XCoreLowerThreadLocal : public ModulePass {
  42     static char ID;
  43
  44     XCoreLowerThreadLocal() : ModulePass(ID) {
  45       initializeXCoreLowerThreadLocalPass(*PassRegistry::getPassRegistry());
  46     }
  47
  48     bool lowerGlobal(GlobalVariable *GV);
  49
  50     bool runOnModule(Module &M) override;
  51   };
  52 }
  53
  54 char XCoreLowerThreadLocal::ID = 0;
  55
  56 INITIALIZE_PASS(XCoreLowerThreadLocal, "xcore-lower-thread-local",
  57                 "Lower thread local variables", false, false)
  58
  59 ModulePass *llvm::createXCoreLowerThreadLocalPass() {
  60   return new XCoreLowerThreadLocal();
  61 }
  62
  63 static ArrayType *createLoweredType(Type *OriginalType) {
  64   return ArrayType::get(OriginalType, MaxThreads);
  65 }
  66
  67 static Constant *
  68 createLoweredInitializer(ArrayType *NewType, Constant *OriginalInitializer) {
  69   SmallVector<Constant *, 8> Elements(MaxThreads);
  70   for (unsigned i = 0; i != MaxThreads; ++i) {
  71     Elements[i] = OriginalInitializer;
  72   }
  73   return ConstantArray::get(NewType, Elements);
  74 }
  75
  76 static Instruction *
  77 createReplacementInstr(ConstantExpr *CE, Instruction *Instr) {
  78   IRBuilder<NoFolder> Builder(Instr);
  79   unsigned OpCode = CE->getOpcode();
  80   switch (OpCode) {
  81     case Instruction::GetElementPtr: {
  82       SmallVector<Value *,4> CEOpVec(CE->op_begin(), CE->op_end());
  83       ArrayRef<Value *> CEOps(CEOpVec);
  84       return dyn_cast<Instruction>(Builder.CreateInBoundsGEP(
  85           cast<GEPOperator>(CE)->getSourceElementType(), CEOps[0],
  86           CEOps.slice(1)));
  87     }
  88     case Instruction::Add:
  89     case Instruction::Sub:
  90     case Instruction::Mul:
  91     case Instruction::UDiv:
  92     case Instruction::SDiv:
  93     case Instruction::FDiv:
  94     case Instruction::URem:
  95     case Instruction::SRem:
  96     case Instruction::FRem:
  97     case Instruction::Shl:
  98     case Instruction::LShr:
  99     case Instruction::AShr:
 100     case Instruction::And:
 101     case Instruction::Or:
 102     case Instruction::Xor:
 103       return dyn_cast<Instruction>(
 104                   Builder.CreateBinOp((Instruction::BinaryOps)OpCode,
 105                                       CE->getOperand(0), CE->getOperand(1),
 106                                       CE->getName()));
 107     case Instruction::Trunc:
 108     case Instruction::ZExt:
 109     case Instruction::SExt:
 110     case Instruction::FPToUI:
 111     case Instruction::FPToSI:
 112     case Instruction::UIToFP:
 113     case Instruction::SIToFP:
 114     case Instruction::FPTrunc:
 115     case Instruction::FPExt:
 116     case Instruction::PtrToInt:
 117     case Instruction::IntToPtr:
 118     case Instruction::BitCast:
 119       return dyn_cast<Instruction>(
 120                   Builder.CreateCast((Instruction::CastOps)OpCode,
 121                                      CE->getOperand(0), CE->getType(),
 122                                      CE->getName()));
 123     default:
 124       llvm_unreachable("Unhandled constant expression!\n");
 125   }
 126 }
 127
 128 static bool replaceConstantExprOp(ConstantExpr *CE, Pass *P) {
 129   do {
 130     SmallVector<WeakTrackingVH, 8> WUsers(CE->user_begin(), CE->user_end());
 131     llvm::sort(WUsers);
 132     WUsers.erase(std::unique(WUsers.begin(), WUsers.end()), WUsers.end());
 133     while (!WUsers.empty())
 134       if (WeakTrackingVH WU = WUsers.pop_back_val()) {
 135         if (PHINode *PN = dyn_cast<PHINode>(WU)) {
 136           for (int I = 0, E = PN->getNumIncomingValues(); I < E; ++I)
 137             if (PN->getIncomingValue(I) == CE) {
 138               BasicBlock *PredBB = PN->getIncomingBlock(I);
 139               if (PredBB->getTerminator()->getNumSuccessors() > 1)
 140                 PredBB = SplitEdge(PredBB, PN->getParent());
 141               Instruction *InsertPos = PredBB->getTerminator();
 142               Instruction *NewInst = createReplacementInstr(CE, InsertPos);
 143               PN->setOperand(I, NewInst);
 144             }
 145         } else if (Instruction *Instr = dyn_cast<Instruction>(WU)) {
 146           Instruction *NewInst = createReplacementInstr(CE, Instr);
 147           Instr->replaceUsesOfWith(CE, NewInst);
 148         } else {
 149           ConstantExpr *CExpr = dyn_cast<ConstantExpr>(WU);
 150           if (!CExpr || !replaceConstantExprOp(CExpr, P))
 151             return false;
 152         }
 153       }
 154   } while (CE->hasNUsesOrMore(1)); // We need to check because a recursive
 155   // sibling may have used 'CE' when createReplacementInstr was called.
 156   CE->destroyConstant();
 157   return true;
 158 }
 159
 160 static bool rewriteNonInstructionUses(GlobalVariable *GV, Pass *P) {
 161   SmallVector<WeakTrackingVH, 8> WUsers;
 162   for (User *U : GV->users())
 163     if (!isa<Instruction>(U))
 164       WUsers.push_back(WeakTrackingVH(U));
 165   while (!WUsers.empty())
 166     if (WeakTrackingVH WU = WUsers.pop_back_val()) {
 167       ConstantExpr *CE = dyn_cast<ConstantExpr>(WU);
 168       if (!CE || !replaceConstantExprOp(CE, P))
 169         return false;
 170     }
 171   return true;
 172 }
 173
 174 static bool isZeroLengthArray(Type *Ty) {
 175   ArrayType *AT = dyn_cast<ArrayType>(Ty);
 176   return AT && (AT->getNumElements() == 0);
 177 }
 178
 179 bool XCoreLowerThreadLocal::lowerGlobal(GlobalVariable *GV) {
 180   Module *M = GV->getParent();
 181   if (!GV->isThreadLocal())
 182     return false;
 183
 184   // Skip globals that we can't lower and leave it for the backend to error.
 185   if (!rewriteNonInstructionUses(GV, this) ||
 186       !GV->getType()->isSized() || isZeroLengthArray(GV->getType()))
 187     return false;
 188
 189   // Create replacement global.
 190   ArrayType *NewType = createLoweredType(GV->getValueType());
 191   Constant *NewInitializer = nullptr;
 192   if (GV->hasInitializer())
 193     NewInitializer = createLoweredInitializer(NewType,
 194                                               GV->getInitializer());
 195   GlobalVariable *NewGV =
 196     new GlobalVariable(*M, NewType, GV->isConstant(), GV->getLinkage(),
 197                        NewInitializer, "", nullptr,
 198                        GlobalVariable::NotThreadLocal,
 199                        GV->getType()->getAddressSpace(),
 200                        GV->isExternallyInitialized());
 201
 202   // Update uses.
 203   SmallVector<User *, 16> Users(GV->user_begin(), GV->user_end());
 204   for (unsigned I = 0, E = Users.size(); I != E; ++I) {
 205     User *U = Users[I];
 206     Instruction *Inst = cast<Instruction>(U);
 207     IRBuilder<> Builder(Inst);
 208     Function *GetID = Intrinsic::getDeclaration(GV->getParent(),
 209                                                 Intrinsic::xcore_getid);
 210     Value *ThreadID = Builder.CreateCall(GetID, {});
 211     Value *Addr = Builder.CreateInBoundsGEP(NewGV->getValueType(), NewGV,
 212                                             {Builder.getInt64(0), ThreadID});
 213     U->replaceUsesOfWith(GV, Addr);
 214   }
 215
 216   // Remove old global.
 217   NewGV->takeName(GV);
 218   GV->eraseFromParent();
 219   return true;
 220 }
 221
 222 bool XCoreLowerThreadLocal::runOnModule(Module &M) {
 223   // Find thread local globals.
 224   bool MadeChange = false;
 225   SmallVector<GlobalVariable *, 16> ThreadLocalGlobals;
 226   for (GlobalVariable &GV : M.globals())
 227     if (GV.isThreadLocal())
 228       ThreadLocalGlobals.push_back(&GV);
 229   for (unsigned I = 0, E = ThreadLocalGlobals.size(); I != E; ++I) {
 230     MadeChange |= lowerGlobal(ThreadLocalGlobals[I]);
 231   }
 232   return MadeChange;
 233 }