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
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__anonffdf90230111::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
replaceConstantExprOp(ConstantExpr * CE,Pass * P)78 static bool replaceConstantExprOp(ConstantExpr *CE, Pass *P) {
79 do {
80 SmallVector<WeakTrackingVH, 8> WUsers(CE->users());
81 llvm::sort(WUsers);
82 WUsers.erase(llvm::unique(WUsers), WUsers.end());
83 while (!WUsers.empty())
84 if (WeakTrackingVH WU = WUsers.pop_back_val()) {
85 if (PHINode *PN = dyn_cast<PHINode>(WU)) {
86 for (int I = 0, E = PN->getNumIncomingValues(); I < E; ++I)
87 if (PN->getIncomingValue(I) == CE) {
88 BasicBlock *PredBB = PN->getIncomingBlock(I);
89 if (PredBB->getTerminator()->getNumSuccessors() > 1)
90 PredBB = SplitEdge(PredBB, PN->getParent());
91 BasicBlock::iterator InsertPos =
92 PredBB->getTerminator()->getIterator();
93 Instruction *NewInst = CE->getAsInstruction();
94 NewInst->insertBefore(*PredBB, InsertPos);
95 PN->setOperand(I, NewInst);
96 }
97 } else if (Instruction *Instr = dyn_cast<Instruction>(WU)) {
98 Instruction *NewInst = CE->getAsInstruction();
99 NewInst->insertBefore(*Instr->getParent(), Instr->getIterator());
100 Instr->replaceUsesOfWith(CE, NewInst);
101 } else {
102 ConstantExpr *CExpr = dyn_cast<ConstantExpr>(WU);
103 if (!CExpr || !replaceConstantExprOp(CExpr, P))
104 return false;
105 }
106 }
107 } while (CE->hasNUsesOrMore(1)); // We need to check because a recursive
108 // sibling may have used 'CE' when getAsInstruction was called.
109 CE->destroyConstant();
110 return true;
111 }
112
rewriteNonInstructionUses(GlobalVariable * GV,Pass * P)113 static bool rewriteNonInstructionUses(GlobalVariable *GV, Pass *P) {
114 SmallVector<WeakTrackingVH, 8> WUsers;
115 for (User *U : GV->users())
116 if (!isa<Instruction>(U))
117 WUsers.push_back(WeakTrackingVH(U));
118 while (!WUsers.empty())
119 if (WeakTrackingVH WU = WUsers.pop_back_val()) {
120 ConstantExpr *CE = dyn_cast<ConstantExpr>(WU);
121 if (!CE || !replaceConstantExprOp(CE, P))
122 return false;
123 }
124 return true;
125 }
126
isZeroLengthArray(Type * Ty)127 static bool isZeroLengthArray(Type *Ty) {
128 ArrayType *AT = dyn_cast<ArrayType>(Ty);
129 return AT && (AT->getNumElements() == 0);
130 }
131
lowerGlobal(GlobalVariable * GV)132 bool XCoreLowerThreadLocal::lowerGlobal(GlobalVariable *GV) {
133 Module *M = GV->getParent();
134 if (!GV->isThreadLocal())
135 return false;
136
137 // Skip globals that we can't lower and leave it for the backend to error.
138 if (!rewriteNonInstructionUses(GV, this) ||
139 !GV->getType()->isSized() || isZeroLengthArray(GV->getType()))
140 return false;
141
142 // Create replacement global.
143 ArrayType *NewType = createLoweredType(GV->getValueType());
144 Constant *NewInitializer = nullptr;
145 if (GV->hasInitializer())
146 NewInitializer = createLoweredInitializer(NewType,
147 GV->getInitializer());
148 GlobalVariable *NewGV =
149 new GlobalVariable(*M, NewType, GV->isConstant(), GV->getLinkage(),
150 NewInitializer, "", nullptr,
151 GlobalVariable::NotThreadLocal,
152 GV->getType()->getAddressSpace(),
153 GV->isExternallyInitialized());
154
155 // Update uses.
156 SmallVector<User *, 16> Users(GV->users());
157 for (User *U : Users) {
158 Instruction *Inst = cast<Instruction>(U);
159 IRBuilder<> Builder(Inst);
160 Function *GetID = Intrinsic::getDeclaration(GV->getParent(),
161 Intrinsic::xcore_getid);
162 Value *ThreadID = Builder.CreateCall(GetID, {});
163 Value *Addr = Builder.CreateInBoundsGEP(NewGV->getValueType(), NewGV,
164 {Builder.getInt64(0), ThreadID});
165 U->replaceUsesOfWith(GV, Addr);
166 }
167
168 // Remove old global.
169 NewGV->takeName(GV);
170 GV->eraseFromParent();
171 return true;
172 }
173
runOnModule(Module & M)174 bool XCoreLowerThreadLocal::runOnModule(Module &M) {
175 // Find thread local globals.
176 bool MadeChange = false;
177 SmallVector<GlobalVariable *, 16> ThreadLocalGlobals;
178 for (GlobalVariable &GV : M.globals())
179 if (GV.isThreadLocal())
180 ThreadLocalGlobals.push_back(&GV);
181 for (GlobalVariable *GV : ThreadLocalGlobals)
182 MadeChange |= lowerGlobal(GV);
183 return MadeChange;
184 }
185