LLVM 17.0.0git
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1//===- LowerEmuTLS.cpp - Add __emutls_[vt].* variables --------------------===//
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
9// This transformation is required for targets depending on libgcc style
10// emulated thread local storage variables. For every defined TLS variable xyz,
11// an __emutls_v.xyz is generated. If there is non-zero initialized value
12// an __emutls_t.xyz is also generated.
17#include "llvm/CodeGen/Passes.h"
19#include "llvm/IR/Constants.h"
20#include "llvm/IR/Module.h"
22#include "llvm/Pass.h"
25using namespace llvm;
27#define DEBUG_TYPE "loweremutls"
29namespace {
31class LowerEmuTLS : public ModulePass {
33 static char ID; // Pass identification, replacement for typeid
34 LowerEmuTLS() : ModulePass(ID) {
36 }
38 bool runOnModule(Module &M) override;
40 bool addEmuTlsVar(Module &M, const GlobalVariable *GV);
41 static void copyLinkageVisibility(Module &M,
42 const GlobalVariable *from,
43 GlobalVariable *to) {
44 to->setLinkage(from->getLinkage());
45 to->setVisibility(from->getVisibility());
46 to->setDSOLocal(from->isDSOLocal());
47 if (from->hasComdat()) {
48 to->setComdat(M.getOrInsertComdat(to->getName()));
50 }
51 }
55char LowerEmuTLS::ID = 0;
58 "Add __emutls_[vt]. variables for emultated TLS model", false,
59 false)
61ModulePass *llvm::createLowerEmuTLSPass() { return new LowerEmuTLS(); }
63bool LowerEmuTLS::runOnModule(Module &M) {
64 if (skipModule(M))
65 return false;
67 auto *TPC = getAnalysisIfAvailable<TargetPassConfig>();
68 if (!TPC)
69 return false;
71 auto &TM = TPC->getTM<TargetMachine>();
72 if (!TM.useEmulatedTLS())
73 return false;
75 bool Changed = false;
77 for (const auto &G : M.globals()) {
78 if (G.isThreadLocal())
79 TlsVars.append({&G});
80 }
81 for (const auto *const G : TlsVars)
82 Changed |= addEmuTlsVar(M, G);
83 return Changed;
86bool LowerEmuTLS::addEmuTlsVar(Module &M, const GlobalVariable *GV) {
87 LLVMContext &C = M.getContext();
88 PointerType *VoidPtrType = Type::getInt8PtrTy(C);
90 std::string EmuTlsVarName = ("__emutls_v." + GV->getName()).str();
91 GlobalVariable *EmuTlsVar = M.getNamedGlobal(EmuTlsVarName);
92 if (EmuTlsVar)
93 return false; // It has been added before.
95 const DataLayout &DL = M.getDataLayout();
96 Constant *NullPtr = ConstantPointerNull::get(VoidPtrType);
98 // Get non-zero initializer from GV's initializer.
99 const Constant *InitValue = nullptr;
100 if (GV->hasInitializer()) {
101 InitValue = GV->getInitializer();
102 const ConstantInt *InitIntValue = dyn_cast<ConstantInt>(InitValue);
103 // When GV's init value is all 0, omit the EmuTlsTmplVar and let
104 // the emutls library function to reset newly allocated TLS variables.
105 if (isa<ConstantAggregateZero>(InitValue) ||
106 (InitIntValue && InitIntValue->isZero()))
107 InitValue = nullptr;
108 }
110 // Create the __emutls_v. symbol, whose type has 4 fields:
111 // word size; // size of GV in bytes
112 // word align; // alignment of GV
113 // void *ptr; // initialized to 0; set at run time per thread.
114 // void *templ; // 0 or point to __emutls_t.*
115 // sizeof(word) should be the same as sizeof(void*) on target.
116 IntegerType *WordType = DL.getIntPtrType(C);
117 PointerType *InitPtrType = InitValue ?
118 PointerType::getUnqual(InitValue->getType()) : VoidPtrType;
119 Type *ElementTypes[4] = {WordType, WordType, VoidPtrType, InitPtrType};
120 ArrayRef<Type*> ElementTypeArray(ElementTypes, 4);
121 StructType *EmuTlsVarType = StructType::create(ElementTypeArray);
122 EmuTlsVar = cast<GlobalVariable>(
123 M.getOrInsertGlobal(EmuTlsVarName, EmuTlsVarType));
124 copyLinkageVisibility(M, GV, EmuTlsVar);
126 // Define "__emutls_t.*" and "__emutls_v.*" only if GV is defined.
127 if (!GV->hasInitializer())
128 return true;
130 Type *GVType = GV->getValueType();
131 Align GVAlignment = DL.getValueOrABITypeAlignment(GV->getAlign(), GVType);
133 // Define "__emutls_t.*" if there is InitValue
134 GlobalVariable *EmuTlsTmplVar = nullptr;
135 if (InitValue) {
136 std::string EmuTlsTmplName = ("__emutls_t." + GV->getName()).str();
137 EmuTlsTmplVar = dyn_cast_or_null<GlobalVariable>(
138 M.getOrInsertGlobal(EmuTlsTmplName, GVType));
139 assert(EmuTlsTmplVar && "Failed to create emualted TLS initializer");
140 EmuTlsTmplVar->setConstant(true);
141 EmuTlsTmplVar->setInitializer(const_cast<Constant*>(InitValue));
142 EmuTlsTmplVar->setAlignment(GVAlignment);
143 copyLinkageVisibility(M, GV, EmuTlsTmplVar);
144 }
146 // Define "__emutls_v.*" with initializer and alignment.
147 Constant *ElementValues[4] = {
148 ConstantInt::get(WordType, DL.getTypeStoreSize(GVType)),
149 ConstantInt::get(WordType, GVAlignment.value()), NullPtr,
150 EmuTlsTmplVar ? EmuTlsTmplVar : NullPtr};
151 ArrayRef<Constant*> ElementValueArray(ElementValues, 4);
152 EmuTlsVar->setInitializer(
153 ConstantStruct::get(EmuTlsVarType, ElementValueArray));
154 Align MaxAlignment =
155 std::max(DL.getABITypeAlign(WordType), DL.getABITypeAlign(VoidPtrType));
156 EmuTlsVar->setAlignment(MaxAlignment);
157 return true;
MachineBasicBlock MachineBasicBlock::iterator DebugLoc DL
This file contains the declarations for the subclasses of Constant, which represent the different fla...
#define DEBUG_TYPE
Definition: LowerEmuTLS.cpp:27
#define G(x, y, z)
Definition: MD5.cpp:56
Module.h This file contains the declarations for the Module class.
const char LLVMTargetMachineRef TM
#define INITIALIZE_PASS(passName, arg, name, cfg, analysis)
Definition: PassSupport.h:38
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
This file defines the SmallVector class.
Target-Independent Code Generator Pass Configuration Options pass.
ArrayRef - Represent a constant reference to an array (0 or more elements consecutively in memory),...
Definition: ArrayRef.h:41
void setSelectionKind(SelectionKind Val)
Definition: Comdat.h:47
SelectionKind getSelectionKind() const
Definition: Comdat.h:46
This is the shared class of boolean and integer constants.
Definition: Constants.h:78
bool isZero() const
This is just a convenience method to make client code smaller for a common code.
Definition: Constants.h:197
static Constant * get(Type *Ty, uint64_t V, bool IsSigned=false)
If Ty is a vector type, return a Constant with a splat of the given value.
Definition: Constants.cpp:888
static ConstantPointerNull * get(PointerType *T)
Static factory methods - Return objects of the specified value.
Definition: Constants.cpp:1691
static Constant * get(StructType *T, ArrayRef< Constant * > V)
Definition: Constants.cpp:1300
This is an important base class in LLVM.
Definition: Constant.h:41
A parsed version of the target data layout string in and methods for querying it.
Definition: DataLayout.h:110
MaybeAlign getAlign() const
Returns the alignment of the given variable or function.
Definition: GlobalObject.h:79
void setAlignment(Align Align)
Sets the alignment attribute of the GlobalObject.
Definition: Globals.cpp:128
void setComdat(Comdat *C)
Definition: Globals.cpp:196
bool hasComdat() const
Definition: GlobalObject.h:127
const Comdat * getComdat() const
Definition: GlobalObject.h:128
bool isDSOLocal() const
Definition: GlobalValue.h:301
VisibilityTypes getVisibility() const
Definition: GlobalValue.h:244
LinkageTypes getLinkage() const
Definition: GlobalValue.h:541
void setLinkage(LinkageTypes LT)
Definition: GlobalValue.h:532
void setDSOLocal(bool Local)
Definition: GlobalValue.h:299
void setVisibility(VisibilityTypes V)
Definition: GlobalValue.h:250
Type * getValueType() const
Definition: GlobalValue.h:292
const Constant * getInitializer() const
getInitializer - Return the initializer for this global variable.
void setInitializer(Constant *InitVal)
setInitializer - Sets the initializer for this global variable, removing any existing initializer if ...
Definition: Globals.cpp:458
bool hasInitializer() const
Definitions have initializers, declarations don't.
void setConstant(bool Val)
Class to represent integer types.
Definition: DerivedTypes.h:40
This is an important class for using LLVM in a threaded context.
Definition: LLVMContext.h:67
ModulePass class - This class is used to implement unstructured interprocedural optimizations and ana...
Definition: Pass.h:251
virtual bool runOnModule(Module &M)=0
runOnModule - Virtual method overriden by subclasses to process the module being operated on.
A Module instance is used to store all the information related to an LLVM module.
Definition: Module.h:65
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
void append(ItTy in_start, ItTy in_end)
Add the specified range to the end of the SmallVector.
Definition: SmallVector.h:687
This is a 'vector' (really, a variable-sized array), optimized for the case when the array is small.
Definition: SmallVector.h:1200
Class to represent struct types.
Definition: DerivedTypes.h:213
static StructType * create(LLVMContext &Context, StringRef Name)
This creates an identified struct.
Definition: Type.cpp:574
Primary interface to the complete machine description for the target machine.
Definition: TargetMachine.h:78
The instances of the Type class are immutable: once they are created, they are never changed.
Definition: Type.h:45
static PointerType * getInt8PtrTy(LLVMContext &C, unsigned AS=0)
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:255
StringRef getName() const
Return a constant reference to the value's name.
Definition: Value.cpp:309
unsigned ID
LLVM IR allows to use arbitrary numbers as calling convention identifiers.
Definition: CallingConv.h:24
@ C
The default llvm calling convention, compatible with C.
Definition: CallingConv.h:34
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
ModulePass * createLowerEmuTLSPass()
LowerEmuTLS - This pass generates __emutls_[vt].xyz variables for all TLS variables for the emulated ...
void initializeLowerEmuTLSPass(PassRegistry &)
This struct is a compact representation of a valid (non-zero power of two) alignment.
Definition: Alignment.h:39
uint64_t value() const
This is a hole in the type system and should not be abused.
Definition: Alignment.h:85