llvm/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/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 }