LLVM 19.0.0git
AMDGPUCtorDtorLowering.cpp
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1//===-- AMDGPUCtorDtorLowering.cpp - Handle global ctors and dtors --------===//
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 pass creates a unified init and fini kernel with the required metadata
11//===----------------------------------------------------------------------===//
12
14#include "AMDGPU.h"
15#include "llvm/IR/Constants.h"
16#include "llvm/IR/Function.h"
18#include "llvm/IR/IRBuilder.h"
19#include "llvm/IR/Module.h"
20#include "llvm/IR/Value.h"
21#include "llvm/Pass.h"
23
24using namespace llvm;
25
26#define DEBUG_TYPE "amdgpu-lower-ctor-dtor"
27
28namespace {
29
30static Function *createInitOrFiniKernelFunction(Module &M, bool IsCtor) {
31 StringRef InitOrFiniKernelName = "amdgcn.device.init";
32 if (!IsCtor)
33 InitOrFiniKernelName = "amdgcn.device.fini";
34 if (M.getFunction(InitOrFiniKernelName))
35 return nullptr;
36
37 Function *InitOrFiniKernel = Function::createWithDefaultAttr(
38 FunctionType::get(Type::getVoidTy(M.getContext()), false),
39 GlobalValue::WeakODRLinkage, 0, InitOrFiniKernelName, &M);
41 InitOrFiniKernel->addFnAttr("amdgpu-flat-work-group-size", "1,1");
42 if (IsCtor)
43 InitOrFiniKernel->addFnAttr("device-init");
44 else
45 InitOrFiniKernel->addFnAttr("device-fini");
46 return InitOrFiniKernel;
47}
48
49// The linker will provide the associated symbols to allow us to traverse the
50// global constructors / destructors in priority order. We create the IR
51// required to call each callback in this section. This is equivalent to the
52// following code.
53//
54// extern "C" void * __init_array_start[];
55// extern "C" void * __init_array_end[];
56// extern "C" void * __fini_array_start[];
57// extern "C" void * __fini_array_end[];
58//
59// using InitCallback = void();
60// using FiniCallback = void(void);
61//
62// void call_init_array_callbacks() {
63// for (auto start = __init_array_start; start != __init_array_end; ++start)
64// reinterpret_cast<InitCallback *>(*start)();
65// }
66//
67// void call_fini_array_callbacks() {
68// size_t fini_array_size = __fini_array_end - __fini_array_start;
69// for (size_t i = fini_array_size; i > 0; --i)
70// reinterpret_cast<FiniCallback *>(__fini_array_start[i - 1])();
71// }
72static void createInitOrFiniCalls(Function &F, bool IsCtor) {
73 Module &M = *F.getParent();
74 LLVMContext &C = M.getContext();
75
76 IRBuilder<> IRB(BasicBlock::Create(C, "entry", &F));
77 auto *LoopBB = BasicBlock::Create(C, "while.entry", &F);
78 auto *ExitBB = BasicBlock::Create(C, "while.end", &F);
80
81 auto *Begin = M.getOrInsertGlobal(
82 IsCtor ? "__init_array_start" : "__fini_array_start",
83 ArrayType::get(PtrTy, 0), [&]() {
84 return new GlobalVariable(
85 M, ArrayType::get(PtrTy, 0),
86 /*isConstant=*/true, GlobalValue::ExternalLinkage,
87 /*Initializer=*/nullptr,
88 IsCtor ? "__init_array_start" : "__fini_array_start",
89 /*InsertBefore=*/nullptr, GlobalVariable::NotThreadLocal,
90 /*AddressSpace=*/1);
91 });
92 auto *End = M.getOrInsertGlobal(
93 IsCtor ? "__init_array_end" : "__fini_array_end",
94 ArrayType::get(PtrTy, 0), [&]() {
95 return new GlobalVariable(
96 M, ArrayType::get(PtrTy, 0),
97 /*isConstant=*/true, GlobalValue::ExternalLinkage,
98 /*Initializer=*/nullptr,
99 IsCtor ? "__init_array_end" : "__fini_array_end",
100 /*InsertBefore=*/nullptr, GlobalVariable::NotThreadLocal,
101 /*AddressSpace=*/1);
102 });
103
104 // The constructor type is suppoed to allow using the argument vectors, but
105 // for now we just call them with no arguments.
106 auto *CallBackTy = FunctionType::get(IRB.getVoidTy(), {});
107
108 Value *Start = Begin;
109 Value *Stop = End;
110 // The destructor array must be called in reverse order. Get a constant
111 // expression to the end of the array and iterate backwards instead.
112 if (!IsCtor) {
113 Type *Int64Ty = IntegerType::getInt64Ty(C);
114 auto *EndPtr = IRB.CreatePtrToInt(End, Int64Ty);
115 auto *BeginPtr = IRB.CreatePtrToInt(Begin, Int64Ty);
116 auto *ByteSize = IRB.CreateSub(EndPtr, BeginPtr);
117 auto *Size = IRB.CreateAShr(ByteSize, ConstantInt::get(Int64Ty, 3));
118 auto *Offset = IRB.CreateSub(Size, ConstantInt::get(Int64Ty, 1));
119 Start = IRB.CreateInBoundsGEP(
120 ArrayType::get(IRB.getPtrTy(), 0), Begin,
121 ArrayRef<Value *>({ConstantInt::get(Int64Ty, 0), Offset}));
122 Stop = Begin;
123 }
124
125 IRB.CreateCondBr(
126 IRB.CreateCmp(IsCtor ? ICmpInst::ICMP_NE : ICmpInst::ICMP_UGE, Start,
127 Stop),
128 LoopBB, ExitBB);
129 IRB.SetInsertPoint(LoopBB);
130 auto *CallBackPHI = IRB.CreatePHI(PtrTy, 2, "ptr");
131 auto *CallBack = IRB.CreateLoad(IRB.getPtrTy(F.getAddressSpace()),
132 CallBackPHI, "callback");
133 IRB.CreateCall(CallBackTy, CallBack);
134 auto *NewCallBack =
135 IRB.CreateConstGEP1_64(PtrTy, CallBackPHI, IsCtor ? 1 : -1, "next");
136 auto *EndCmp = IRB.CreateCmp(IsCtor ? ICmpInst::ICMP_EQ : ICmpInst::ICMP_ULT,
137 NewCallBack, Stop, "end");
138 CallBackPHI->addIncoming(Start, &F.getEntryBlock());
139 CallBackPHI->addIncoming(NewCallBack, LoopBB);
140 IRB.CreateCondBr(EndCmp, ExitBB, LoopBB);
141 IRB.SetInsertPoint(ExitBB);
142 IRB.CreateRetVoid();
143}
144
145static bool createInitOrFiniKernel(Module &M, StringRef GlobalName,
146 bool IsCtor) {
147 GlobalVariable *GV = M.getGlobalVariable(GlobalName);
148 if (!GV || !GV->hasInitializer())
149 return false;
150 ConstantArray *GA = dyn_cast<ConstantArray>(GV->getInitializer());
151 if (!GA || GA->getNumOperands() == 0)
152 return false;
153
154 Function *InitOrFiniKernel = createInitOrFiniKernelFunction(M, IsCtor);
155 if (!InitOrFiniKernel)
156 return false;
157
158 createInitOrFiniCalls(*InitOrFiniKernel, IsCtor);
159
160 appendToUsed(M, {InitOrFiniKernel});
161 return true;
162}
163
164static bool lowerCtorsAndDtors(Module &M) {
165 bool Modified = false;
166 Modified |= createInitOrFiniKernel(M, "llvm.global_ctors", /*IsCtor =*/true);
167 Modified |= createInitOrFiniKernel(M, "llvm.global_dtors", /*IsCtor =*/false);
168 return Modified;
169}
170
171class AMDGPUCtorDtorLoweringLegacy final : public ModulePass {
172public:
173 static char ID;
174 AMDGPUCtorDtorLoweringLegacy() : ModulePass(ID) {}
175 bool runOnModule(Module &M) override { return lowerCtorsAndDtors(M); }
176};
177
178} // End anonymous namespace
179
182 return lowerCtorsAndDtors(M) ? PreservedAnalyses::none()
184}
185
186char AMDGPUCtorDtorLoweringLegacy::ID = 0;
188 AMDGPUCtorDtorLoweringLegacy::ID;
189INITIALIZE_PASS(AMDGPUCtorDtorLoweringLegacy, DEBUG_TYPE,
190 "Lower ctors and dtors for AMDGPU", false, false)
191
193 return new AMDGPUCtorDtorLoweringLegacy();
194}
This file contains the declarations for the subclasses of Constant, which represent the different fla...
uint64_t Size
bool End
Definition: ELF_riscv.cpp:480
#define DEBUG_TYPE
#define F(x, y, z)
Definition: MD5.cpp:55
Module.h This file contains the declarations for the Module class.
#define INITIALIZE_PASS(passName, arg, name, cfg, analysis)
Definition: PassSupport.h:38
PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM)
A container for analyses that lazily runs them and caches their results.
Definition: PassManager.h:321
ArrayRef - Represent a constant reference to an array (0 or more elements consecutively in memory),...
Definition: ArrayRef.h:41
static BasicBlock * Create(LLVMContext &Context, const Twine &Name="", Function *Parent=nullptr, BasicBlock *InsertBefore=nullptr)
Creates a new BasicBlock.
Definition: BasicBlock.h:199
ConstantArray - Constant Array Declarations.
Definition: Constants.h:423
void addFnAttr(Attribute::AttrKind Kind)
Add function attributes to this function.
Definition: Function.cpp:593
static Function * createWithDefaultAttr(FunctionType *Ty, LinkageTypes Linkage, unsigned AddrSpace, const Twine &N="", Module *M=nullptr)
Creates a function with some attributes recorded in llvm.module.flags applied.
Definition: Function.cpp:373
void setCallingConv(CallingConv::ID CC)
Definition: Function.h:267
@ WeakODRLinkage
Same, but only replaced by something equivalent.
Definition: GlobalValue.h:57
@ ExternalLinkage
Externally visible function.
Definition: GlobalValue.h:52
const Constant * getInitializer() const
getInitializer - Return the initializer for this global variable.
bool hasInitializer() const
Definitions have initializers, declarations don't.
Value * CreateConstGEP1_64(Type *Ty, Value *Ptr, uint64_t Idx0, const Twine &Name="")
Definition: IRBuilder.h:1927
Value * CreateInBoundsGEP(Type *Ty, Value *Ptr, ArrayRef< Value * > IdxList, const Twine &Name="")
Definition: IRBuilder.h:1876
Value * CreateCmp(CmpInst::Predicate Pred, Value *LHS, Value *RHS, const Twine &Name="", MDNode *FPMathTag=nullptr)
Definition: IRBuilder.h:2366
PHINode * CreatePHI(Type *Ty, unsigned NumReservedValues, const Twine &Name="")
Definition: IRBuilder.h:2397
Value * CreateSub(Value *LHS, Value *RHS, const Twine &Name="", bool HasNUW=false, bool HasNSW=false)
Definition: IRBuilder.h:1344
BranchInst * CreateCondBr(Value *Cond, BasicBlock *True, BasicBlock *False, MDNode *BranchWeights=nullptr, MDNode *Unpredictable=nullptr)
Create a conditional 'br Cond, TrueDest, FalseDest' instruction.
Definition: IRBuilder.h:1120
LoadInst * CreateLoad(Type *Ty, Value *Ptr, const char *Name)
Provided to resolve 'CreateLoad(Ty, Ptr, "...")' correctly, instead of converting the string to 'bool...
Definition: IRBuilder.h:1790
ReturnInst * CreateRetVoid()
Create a 'ret void' instruction.
Definition: IRBuilder.h:1090
Value * CreatePtrToInt(Value *V, Type *DestTy, const Twine &Name="")
Definition: IRBuilder.h:2117
PointerType * getPtrTy(unsigned AddrSpace=0)
Fetch the type representing a pointer.
Definition: IRBuilder.h:569
void SetInsertPoint(BasicBlock *TheBB)
This specifies that created instructions should be appended to the end of the specified block.
Definition: IRBuilder.h:180
Type * getVoidTy()
Fetch the type representing void.
Definition: IRBuilder.h:564
CallInst * CreateCall(FunctionType *FTy, Value *Callee, ArrayRef< Value * > Args=std::nullopt, const Twine &Name="", MDNode *FPMathTag=nullptr)
Definition: IRBuilder.h:2412
Value * CreateAShr(Value *LHS, Value *RHS, const Twine &Name="", bool isExact=false)
Definition: IRBuilder.h:1456
This provides a uniform API for creating instructions and inserting them into a basic block: either a...
Definition: IRBuilder.h:2666
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
A set of analyses that are preserved following a run of a transformation pass.
Definition: Analysis.h:109
static PreservedAnalyses none()
Convenience factory function for the empty preserved set.
Definition: Analysis.h:112
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
Definition: Analysis.h:115
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:50
The instances of the Type class are immutable: once they are created, they are never changed.
Definition: Type.h:45
static Type * getVoidTy(LLVMContext &C)
unsigned getNumOperands() const
Definition: User.h:191
LLVM Value Representation.
Definition: Value.h:74
@ GLOBAL_ADDRESS
Address space for global memory (RAT0, VTX0).
unsigned ID
LLVM IR allows to use arbitrary numbers as calling convention identifiers.
Definition: CallingConv.h:24
@ AMDGPU_KERNEL
Used for AMDGPU code object kernels.
Definition: CallingConv.h:200
@ 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
@ Offset
Definition: DWP.cpp:456
char & AMDGPUCtorDtorLoweringLegacyPassID
ModulePass * createAMDGPUCtorDtorLoweringLegacyPass()
void appendToUsed(Module &M, ArrayRef< GlobalValue * > Values)
Adds global values to the llvm.used list.