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
28using namespace llvm;
29
30static 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
35namespace {
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
52char XCoreLowerThreadLocal::ID = 0;
53
54INITIALIZE_PASS(XCoreLowerThreadLocal, "xcore-lower-thread-local",
55                "Lower thread local variables", false, false)
56
57ModulePass *llvm::createXCoreLowerThreadLocalPass() {
58  return new XCoreLowerThreadLocal();
59}
60
61static ArrayType *createLoweredType(Type *OriginalType) {
62  return ArrayType::get(OriginalType, MaxThreads);
63}
64
65static Constant *
66createLoweredInitializer(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
74static 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
83static bool isZeroLengthArray(Type *Ty) {
84  ArrayType *AT = dyn_cast<ArrayType>(Ty);
85  return AT && (AT->getNumElements() == 0);
86}
87
88bool 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
131bool 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