XCoreLowerThreadLocal.cpp revision 288943 
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/IRBuilder.h"
21#include "llvm/IR/Intrinsics.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
31using namespace llvm;
32
33static 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
38namespace {
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
55char XCoreLowerThreadLocal::ID = 0;
56
57INITIALIZE_PASS(XCoreLowerThreadLocal, "xcore-lower-thread-local",
58                "Lower thread local variables", false, false)
59
60ModulePass *llvm::createXCoreLowerThreadLocalPass() {
61  return new XCoreLowerThreadLocal();
62}
63
64static ArrayType *createLoweredType(Type *OriginalType) {
65  return ArrayType::get(OriginalType, MaxThreads);
66}
67
68static Constant *
69createLoweredInitializer(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
77static Instruction *
78createReplacementInstr(ConstantExpr *CE, Instruction *Instr) {
79  IRBuilder<true,NoFolder> Builder(Instr);
80  unsigned OpCode = CE->getOpcode();
81  switch (OpCode) {
82    case Instruction::GetElementPtr: {
83      SmallVector<Value *,4> CEOpVec(CE->op_begin(), CE->op_end());
84      ArrayRef<Value *> CEOps(CEOpVec);
85      return dyn_cast<Instruction>(Builder.CreateInBoundsGEP(
86          cast<GEPOperator>(CE)->getSourceElementType(), CEOps[0],
87          CEOps.slice(1)));
88    }
89    case Instruction::Add:
90    case Instruction::Sub:
91    case Instruction::Mul:
92    case Instruction::UDiv:
93    case Instruction::SDiv:
94    case Instruction::FDiv:
95    case Instruction::URem:
96    case Instruction::SRem:
97    case Instruction::FRem:
98    case Instruction::Shl:
99    case Instruction::LShr:
100    case Instruction::AShr:
101    case Instruction::And:
102    case Instruction::Or:
103    case Instruction::Xor:
104      return dyn_cast<Instruction>(
105                  Builder.CreateBinOp((Instruction::BinaryOps)OpCode,
106                                      CE->getOperand(0), CE->getOperand(1),
107                                      CE->getName()));
108    case Instruction::Trunc:
109    case Instruction::ZExt:
110    case Instruction::SExt:
111    case Instruction::FPToUI:
112    case Instruction::FPToSI:
113    case Instruction::UIToFP:
114    case Instruction::SIToFP:
115    case Instruction::FPTrunc:
116    case Instruction::FPExt:
117    case Instruction::PtrToInt:
118    case Instruction::IntToPtr:
119    case Instruction::BitCast:
120      return dyn_cast<Instruction>(
121                  Builder.CreateCast((Instruction::CastOps)OpCode,
122                                     CE->getOperand(0), CE->getType(),
123                                     CE->getName()));
124    default:
125      llvm_unreachable("Unhandled constant expression!\n");
126  }
127}
128
129static bool replaceConstantExprOp(ConstantExpr *CE, Pass *P) {
130  do {
131    SmallVector<WeakVH,8> WUsers(CE->user_begin(), CE->user_end());
132    std::sort(WUsers.begin(), WUsers.end());
133    WUsers.erase(std::unique(WUsers.begin(), WUsers.end()), WUsers.end());
134    while (!WUsers.empty())
135      if (WeakVH WU = WUsers.pop_back_val()) {
136        if (PHINode *PN = dyn_cast<PHINode>(WU)) {
137          for (int I = 0, E = PN->getNumIncomingValues(); I < E; ++I)
138            if (PN->getIncomingValue(I) == CE) {
139              BasicBlock *PredBB = PN->getIncomingBlock(I);
140              if (PredBB->getTerminator()->getNumSuccessors() > 1)
141                PredBB = SplitEdge(PredBB, PN->getParent());
142              Instruction *InsertPos = PredBB->getTerminator();
143              Instruction *NewInst = createReplacementInstr(CE, InsertPos);
144              PN->setOperand(I, NewInst);
145            }
146        } else if (Instruction *Instr = dyn_cast<Instruction>(WU)) {
147          Instruction *NewInst = createReplacementInstr(CE, Instr);
148          Instr->replaceUsesOfWith(CE, NewInst);
149        } else {
150          ConstantExpr *CExpr = dyn_cast<ConstantExpr>(WU);
151          if (!CExpr || !replaceConstantExprOp(CExpr, P))
152            return false;
153        }
154      }
155  } while (CE->hasNUsesOrMore(1)); // We need to check because a recursive
156  // sibling may have used 'CE' when createReplacementInstr was called.
157  CE->destroyConstant();
158  return true;
159}
160
161static bool rewriteNonInstructionUses(GlobalVariable *GV, Pass *P) {
162  SmallVector<WeakVH,8> WUsers;
163  for (User *U : GV->users())
164    if (!isa<Instruction>(U))
165      WUsers.push_back(WeakVH(U));
166  while (!WUsers.empty())
167    if (WeakVH WU = WUsers.pop_back_val()) {
168      ConstantExpr *CE = dyn_cast<ConstantExpr>(WU);
169      if (!CE || !replaceConstantExprOp(CE, P))
170        return false;
171    }
172  return true;
173}
174
175static bool isZeroLengthArray(Type *Ty) {
176  ArrayType *AT = dyn_cast<ArrayType>(Ty);
177  return AT && (AT->getNumElements() == 0);
178}
179
180bool XCoreLowerThreadLocal::lowerGlobal(GlobalVariable *GV) {
181  Module *M = GV->getParent();
182  LLVMContext &Ctx = M->getContext();
183  if (!GV->isThreadLocal())
184    return false;
185
186  // Skip globals that we can't lower and leave it for the backend to error.
187  if (!rewriteNonInstructionUses(GV, this) ||
188      !GV->getType()->isSized() || isZeroLengthArray(GV->getType()))
189    return false;
190
191  // Create replacement global.
192  ArrayType *NewType = createLoweredType(GV->getType()->getElementType());
193  Constant *NewInitializer = nullptr;
194  if (GV->hasInitializer())
195    NewInitializer = createLoweredInitializer(NewType,
196                                              GV->getInitializer());
197  GlobalVariable *NewGV =
198    new GlobalVariable(*M, NewType, GV->isConstant(), GV->getLinkage(),
199                       NewInitializer, "", nullptr,
200                       GlobalVariable::NotThreadLocal,
201                       GV->getType()->getAddressSpace(),
202                       GV->isExternallyInitialized());
203
204  // Update uses.
205  SmallVector<User *, 16> Users(GV->user_begin(), GV->user_end());
206  for (unsigned I = 0, E = Users.size(); I != E; ++I) {
207    User *U = Users[I];
208    Instruction *Inst = cast<Instruction>(U);
209    IRBuilder<> Builder(Inst);
210    Function *GetID = Intrinsic::getDeclaration(GV->getParent(),
211                                                Intrinsic::xcore_getid);
212    Value *ThreadID = Builder.CreateCall(GetID, {});
213    SmallVector<Value *, 2> Indices;
214    Indices.push_back(Constant::getNullValue(Type::getInt64Ty(Ctx)));
215    Indices.push_back(ThreadID);
216    Value *Addr =
217        Builder.CreateInBoundsGEP(NewGV->getValueType(), NewGV, Indices);
218    U->replaceUsesOfWith(GV, Addr);
219  }
220
221  // Remove old global.
222  NewGV->takeName(GV);
223  GV->eraseFromParent();
224  return true;
225}
226
227bool XCoreLowerThreadLocal::runOnModule(Module &M) {
228  // Find thread local globals.
229  bool MadeChange = false;
230  SmallVector<GlobalVariable *, 16> ThreadLocalGlobals;
231  for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
232       GVI != E; ++GVI) {
233    GlobalVariable *GV = GVI;
234    if (GV->isThreadLocal())
235      ThreadLocalGlobals.push_back(GV);
236  }
237  for (unsigned I = 0, E = ThreadLocalGlobals.size(); I != E; ++I) {
238    MadeChange |= lowerGlobal(ThreadLocalGlobals[I]);
239  }
240  return MadeChange;
241}
242