XCoreLowerThreadLocal.cpp revision 360784 
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
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<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<WeakTrackingVH, 8> WUsers(CE->user_begin(), CE->user_end());
132    llvm::sort(WUsers);
133    WUsers.erase(std::unique(WUsers.begin(), WUsers.end()), WUsers.end());
134    while (!WUsers.empty())
135      if (WeakTrackingVH 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<WeakTrackingVH, 8> WUsers;
163  for (User *U : GV->users())
164    if (!isa<Instruction>(U))
165      WUsers.push_back(WeakTrackingVH(U));
166  while (!WUsers.empty())
167    if (WeakTrackingVH 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  if (!GV->isThreadLocal())
183    return false;
184
185  // Skip globals that we can't lower and leave it for the backend to error.
186  if (!rewriteNonInstructionUses(GV, this) ||
187      !GV->getType()->isSized() || isZeroLengthArray(GV->getType()))
188    return false;
189
190  // Create replacement global.
191  ArrayType *NewType = createLoweredType(GV->getValueType());
192  Constant *NewInitializer = nullptr;
193  if (GV->hasInitializer())
194    NewInitializer = createLoweredInitializer(NewType,
195                                              GV->getInitializer());
196  GlobalVariable *NewGV =
197    new GlobalVariable(*M, NewType, GV->isConstant(), GV->getLinkage(),
198                       NewInitializer, "", nullptr,
199                       GlobalVariable::NotThreadLocal,
200                       GV->getType()->getAddressSpace(),
201                       GV->isExternallyInitialized());
202
203  // Update uses.
204  SmallVector<User *, 16> Users(GV->user_begin(), GV->user_end());
205  for (unsigned I = 0, E = Users.size(); I != E; ++I) {
206    User *U = Users[I];
207    Instruction *Inst = cast<Instruction>(U);
208    IRBuilder<> Builder(Inst);
209    Function *GetID = Intrinsic::getDeclaration(GV->getParent(),
210                                                Intrinsic::xcore_getid);
211    Value *ThreadID = Builder.CreateCall(GetID, {});
212    Value *Addr = Builder.CreateInBoundsGEP(NewGV->getValueType(), NewGV,
213                                            {Builder.getInt64(0), ThreadID});
214    U->replaceUsesOfWith(GV, Addr);
215  }
216
217  // Remove old global.
218  NewGV->takeName(GV);
219  GV->eraseFromParent();
220  return true;
221}
222
223bool XCoreLowerThreadLocal::runOnModule(Module &M) {
224  // Find thread local globals.
225  bool MadeChange = false;
226  SmallVector<GlobalVariable *, 16> ThreadLocalGlobals;
227  for (GlobalVariable &GV : M.globals())
228    if (GV.isThreadLocal())
229      ThreadLocalGlobals.push_back(&GV);
230  for (unsigned I = 0, E = ThreadLocalGlobals.size(); I != E; ++I) {
231    MadeChange |= lowerGlobal(ThreadLocalGlobals[I]);
232  }
233  return MadeChange;
234}
235