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
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
XCoreLowerThreadLocal__anon071309100111::XCoreLowerThreadLocal45 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
createXCoreLowerThreadLocalPass()60 ModulePass *llvm::createXCoreLowerThreadLocalPass() {
61 return new XCoreLowerThreadLocal();
62 }
63
createLoweredType(Type * OriginalType)64 static ArrayType *createLoweredType(Type *OriginalType) {
65 return ArrayType::get(OriginalType, MaxThreads);
66 }
67
68 static Constant *
createLoweredInitializer(ArrayType * NewType,Constant * OriginalInitializer)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 static Instruction *
createReplacementInstr(ConstantExpr * CE,Instruction * Instr)78 createReplacementInstr(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
replaceConstantExprOp(ConstantExpr * CE,Pass * P)129 static 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
rewriteNonInstructionUses(GlobalVariable * GV,Pass * P)161 static 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
isZeroLengthArray(Type * Ty)175 static bool isZeroLengthArray(Type *Ty) {
176 ArrayType *AT = dyn_cast<ArrayType>(Ty);
177 return AT && (AT->getNumElements() == 0);
178 }
179
lowerGlobal(GlobalVariable * GV)180 bool 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
runOnModule(Module & M)223 bool 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