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/ReplaceConstant.h"
25 #include "llvm/IR/ValueHandle.h"
26 #include "llvm/Pass.h"
27 #include "llvm/Support/CommandLine.h"
28 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
29
30 #define DEBUG_TYPE "xcore-lower-thread-local"
31
32 using namespace llvm;
33
34 static cl::opt<unsigned> MaxThreads(
35 "xcore-max-threads", cl::Optional,
36 cl::desc("Maximum number of threads (for emulation thread-local storage)"),
37 cl::Hidden, cl::value_desc("number"), cl::init(8));
38
39 namespace {
40 /// Lowers thread local variables on the XCore. Each thread local variable is
41 /// expanded to an array of n elements indexed by the thread ID where n is the
42 /// fixed number hardware threads supported by the device.
43 struct XCoreLowerThreadLocal : public ModulePass {
44 static char ID;
45
XCoreLowerThreadLocal__anon722cbd2e0111::XCoreLowerThreadLocal46 XCoreLowerThreadLocal() : ModulePass(ID) {
47 initializeXCoreLowerThreadLocalPass(*PassRegistry::getPassRegistry());
48 }
49
50 bool lowerGlobal(GlobalVariable *GV);
51
52 bool runOnModule(Module &M) override;
53 };
54 }
55
56 char XCoreLowerThreadLocal::ID = 0;
57
58 INITIALIZE_PASS(XCoreLowerThreadLocal, "xcore-lower-thread-local",
59 "Lower thread local variables", false, false)
60
createXCoreLowerThreadLocalPass()61 ModulePass *llvm::createXCoreLowerThreadLocalPass() {
62 return new XCoreLowerThreadLocal();
63 }
64
createLoweredType(Type * OriginalType)65 static ArrayType *createLoweredType(Type *OriginalType) {
66 return ArrayType::get(OriginalType, MaxThreads);
67 }
68
69 static Constant *
createLoweredInitializer(ArrayType * NewType,Constant * OriginalInitializer)70 createLoweredInitializer(ArrayType *NewType, Constant *OriginalInitializer) {
71 SmallVector<Constant *, 8> Elements(MaxThreads);
72 for (unsigned i = 0; i != MaxThreads; ++i) {
73 Elements[i] = OriginalInitializer;
74 }
75 return ConstantArray::get(NewType, Elements);
76 }
77
78
replaceConstantExprOp(ConstantExpr * CE,Pass * P)79 static bool replaceConstantExprOp(ConstantExpr *CE, Pass *P) {
80 do {
81 SmallVector<WeakTrackingVH, 8> WUsers(CE->users());
82 llvm::sort(WUsers);
83 WUsers.erase(std::unique(WUsers.begin(), WUsers.end()), WUsers.end());
84 while (!WUsers.empty())
85 if (WeakTrackingVH WU = WUsers.pop_back_val()) {
86 if (PHINode *PN = dyn_cast<PHINode>(WU)) {
87 for (int I = 0, E = PN->getNumIncomingValues(); I < E; ++I)
88 if (PN->getIncomingValue(I) == CE) {
89 BasicBlock *PredBB = PN->getIncomingBlock(I);
90 if (PredBB->getTerminator()->getNumSuccessors() > 1)
91 PredBB = SplitEdge(PredBB, PN->getParent());
92 Instruction *InsertPos = PredBB->getTerminator();
93 Instruction *NewInst = createReplacementInstr(CE, InsertPos);
94 PN->setOperand(I, NewInst);
95 }
96 } else if (Instruction *Instr = dyn_cast<Instruction>(WU)) {
97 Instruction *NewInst = createReplacementInstr(CE, Instr);
98 Instr->replaceUsesOfWith(CE, NewInst);
99 } else {
100 ConstantExpr *CExpr = dyn_cast<ConstantExpr>(WU);
101 if (!CExpr || !replaceConstantExprOp(CExpr, P))
102 return false;
103 }
104 }
105 } while (CE->hasNUsesOrMore(1)); // We need to check because a recursive
106 // sibling may have used 'CE' when createReplacementInstr was called.
107 CE->destroyConstant();
108 return true;
109 }
110
rewriteNonInstructionUses(GlobalVariable * GV,Pass * P)111 static bool rewriteNonInstructionUses(GlobalVariable *GV, Pass *P) {
112 SmallVector<WeakTrackingVH, 8> WUsers;
113 for (User *U : GV->users())
114 if (!isa<Instruction>(U))
115 WUsers.push_back(WeakTrackingVH(U));
116 while (!WUsers.empty())
117 if (WeakTrackingVH WU = WUsers.pop_back_val()) {
118 ConstantExpr *CE = dyn_cast<ConstantExpr>(WU);
119 if (!CE || !replaceConstantExprOp(CE, P))
120 return false;
121 }
122 return true;
123 }
124
isZeroLengthArray(Type * Ty)125 static bool isZeroLengthArray(Type *Ty) {
126 ArrayType *AT = dyn_cast<ArrayType>(Ty);
127 return AT && (AT->getNumElements() == 0);
128 }
129
lowerGlobal(GlobalVariable * GV)130 bool XCoreLowerThreadLocal::lowerGlobal(GlobalVariable *GV) {
131 Module *M = GV->getParent();
132 if (!GV->isThreadLocal())
133 return false;
134
135 // Skip globals that we can't lower and leave it for the backend to error.
136 if (!rewriteNonInstructionUses(GV, this) ||
137 !GV->getType()->isSized() || isZeroLengthArray(GV->getType()))
138 return false;
139
140 // Create replacement global.
141 ArrayType *NewType = createLoweredType(GV->getValueType());
142 Constant *NewInitializer = nullptr;
143 if (GV->hasInitializer())
144 NewInitializer = createLoweredInitializer(NewType,
145 GV->getInitializer());
146 GlobalVariable *NewGV =
147 new GlobalVariable(*M, NewType, GV->isConstant(), GV->getLinkage(),
148 NewInitializer, "", nullptr,
149 GlobalVariable::NotThreadLocal,
150 GV->getType()->getAddressSpace(),
151 GV->isExternallyInitialized());
152
153 // Update uses.
154 SmallVector<User *, 16> Users(GV->users());
155 for (unsigned I = 0, E = Users.size(); I != E; ++I) {
156 User *U = Users[I];
157 Instruction *Inst = cast<Instruction>(U);
158 IRBuilder<> Builder(Inst);
159 Function *GetID = Intrinsic::getDeclaration(GV->getParent(),
160 Intrinsic::xcore_getid);
161 Value *ThreadID = Builder.CreateCall(GetID, {});
162 Value *Addr = Builder.CreateInBoundsGEP(NewGV->getValueType(), NewGV,
163 {Builder.getInt64(0), ThreadID});
164 U->replaceUsesOfWith(GV, Addr);
165 }
166
167 // Remove old global.
168 NewGV->takeName(GV);
169 GV->eraseFromParent();
170 return true;
171 }
172
runOnModule(Module & M)173 bool XCoreLowerThreadLocal::runOnModule(Module &M) {
174 // Find thread local globals.
175 bool MadeChange = false;
176 SmallVector<GlobalVariable *, 16> ThreadLocalGlobals;
177 for (GlobalVariable &GV : M.globals())
178 if (GV.isThreadLocal())
179 ThreadLocalGlobals.push_back(&GV);
180 for (unsigned I = 0, E = ThreadLocalGlobals.size(); I != E; ++I) {
181 MadeChange |= lowerGlobal(ThreadLocalGlobals[I]);
182 }
183 return MadeChange;
184 }
185