Home | History | Annotate | Download | only in XCore 
      1 //===-- XCoreLowerThreadLocal - Lower thread local variables --------------===//
      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 /// \brief This file contains a pass that lowers thread local variables on the
     12 ///        XCore.
     13 ///
     14 //===----------------------------------------------------------------------===//
     15 
     16 #include "XCore.h"
     17 #include "llvm/IR/Constants.h"
     18 #include "llvm/IR/DerivedTypes.h"
     19 #include "llvm/IR/GlobalVariable.h"
     20 #include "llvm/IR/Intrinsics.h"
     21 #include "llvm/IR/IRBuilder.h"
     22 #include "llvm/IR/Module.h"
     23 #include "llvm/Pass.h"
     24 #include "llvm/Support/CommandLine.h"
     25 
     26 #define DEBUG_TYPE "xcore-lower-thread-local"
     27 
     28 using namespace llvm;
     29 
     30 static cl::opt<unsigned> MaxThreads(
     31   "xcore-max-threads", cl::Optional,
     32   cl::desc("Maximum number of threads (for emulation thread-local storage)"),
     33   cl::Hidden, cl::value_desc("number"), cl::init(8));
     34 
     35 namespace {
     36   /// Lowers thread local variables on the XCore. Each thread local variable is
     37   /// expanded to an array of n elements indexed by the thread ID where n is the
     38   /// fixed number hardware threads supported by the device.
     39   struct XCoreLowerThreadLocal : public ModulePass {
     40     static char ID;
     41 
     42     XCoreLowerThreadLocal() : ModulePass(ID) {
     43       initializeXCoreLowerThreadLocalPass(*PassRegistry::getPassRegistry());
     44     }
     45 
     46     bool lowerGlobal(GlobalVariable *GV);
     47 
     48     bool runOnModule(Module &M);
     49   };
     50 }
     51 
     52 char XCoreLowerThreadLocal::ID = 0;
     53 
     54 INITIALIZE_PASS(XCoreLowerThreadLocal, "xcore-lower-thread-local",
     55                 "Lower thread local variables", false, false)
     56 
     57 ModulePass *llvm::createXCoreLowerThreadLocalPass() {
     58   return new XCoreLowerThreadLocal();
     59 }
     60 
     61 static ArrayType *createLoweredType(Type *OriginalType) {
     62   return ArrayType::get(OriginalType, MaxThreads);
     63 }
     64 
     65 static Constant *
     66 createLoweredInitializer(ArrayType *NewType, Constant *OriginalInitializer) {
     67   SmallVector<Constant *, 8> Elements(MaxThreads);
     68   for (unsigned i = 0; i != MaxThreads; ++i) {
     69     Elements[i] = OriginalInitializer;
     70   }
     71   return ConstantArray::get(NewType, Elements);
     72 }
     73 
     74 static bool hasNonInstructionUse(GlobalVariable *GV) {
     75   for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E;
     76        ++UI)
     77     if (!isa<Instruction>(*UI))
     78       return true;
     79 
     80   return false;
     81 }
     82 
     83 static bool isZeroLengthArray(Type *Ty) {
     84   ArrayType *AT = dyn_cast<ArrayType>(Ty);
     85   return AT && (AT->getNumElements() == 0);
     86 }
     87 
     88 bool XCoreLowerThreadLocal::lowerGlobal(GlobalVariable *GV) {
     89   Module *M = GV->getParent();
     90   LLVMContext &Ctx = M->getContext();
     91   if (!GV->isThreadLocal())
     92     return false;
     93 
     94   // Skip globals that we can't lower and leave it for the backend to error.
     95   if (hasNonInstructionUse(GV) ||
     96       !GV->getType()->isSized() || isZeroLengthArray(GV->getType()))
     97     return false;
     98 
     99   // Create replacement global.
    100   ArrayType *NewType = createLoweredType(GV->getType()->getElementType());
    101   Constant *NewInitializer = createLoweredInitializer(NewType,
    102                                                       GV->getInitializer());
    103   GlobalVariable *NewGV =
    104     new GlobalVariable(*M, NewType, GV->isConstant(), GV->getLinkage(),
    105                        NewInitializer, "", 0, GlobalVariable::NotThreadLocal,
    106                        GV->getType()->getAddressSpace(),
    107                        GV->isExternallyInitialized());
    108 
    109   // Update uses.
    110   SmallVector<User *, 16> Users(GV->use_begin(), GV->use_end());
    111   for (unsigned I = 0, E = Users.size(); I != E; ++I) {
    112     User *U = Users[I];
    113     Instruction *Inst = cast<Instruction>(U);
    114     IRBuilder<> Builder(Inst);
    115     Function *GetID = Intrinsic::getDeclaration(GV->getParent(),
    116                                                 Intrinsic::xcore_getid);
    117     Value *ThreadID = Builder.CreateCall(GetID);
    118     SmallVector<Value *, 2> Indices;
    119     Indices.push_back(Constant::getNullValue(Type::getInt64Ty(Ctx)));
    120     Indices.push_back(ThreadID);
    121     Value *Addr = Builder.CreateInBoundsGEP(NewGV, Indices);
    122     U->replaceUsesOfWith(GV, Addr);
    123   }
    124 
    125   // Remove old global.
    126   NewGV->takeName(GV);
    127   GV->eraseFromParent();
    128   return true;
    129 }
    130 
    131 bool XCoreLowerThreadLocal::runOnModule(Module &M) {
    132   // Find thread local globals.
    133   bool MadeChange = false;
    134   SmallVector<GlobalVariable *, 16> ThreadLocalGlobals;
    135   for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
    136        GVI != E; ++GVI) {
    137     GlobalVariable *GV = GVI;
    138     if (GV->isThreadLocal())
    139       ThreadLocalGlobals.push_back(GV);
    140   }
    141   for (unsigned I = 0, E = ThreadLocalGlobals.size(); I != E; ++I) {
    142     MadeChange |= lowerGlobal(ThreadLocalGlobals[I]);
    143   }
    144   return MadeChange;
    145 }
    146