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 
13 #include "AMDGPUCtorDtorLowering.h"
14 #include "AMDGPU.h"
15 #include "llvm/IR/Constants.h"
16 #include "llvm/IR/Function.h"
17 #include "llvm/IR/GlobalVariable.h"
18 #include "llvm/IR/IRBuilder.h"
19 #include "llvm/IR/Module.h"
20 #include "llvm/IR/Value.h"
21 #include "llvm/Pass.h"
22 #include "llvm/Transforms/Utils/ModuleUtils.h"
23 
24 using namespace llvm;
25 
26 #define DEBUG_TYPE "amdgpu-lower-ctor-dtor"
27 
28 namespace {
29 
30 static Function *createInitOrFiniKernelFunction(Module &M, bool IsCtor) {
31   StringRef InitOrFiniKernelName = "amdgcn.device.init";
32   if (!IsCtor)
33     InitOrFiniKernelName = "amdgcn.device.fini";
34 
35   Function *InitOrFiniKernel = Function::createWithDefaultAttr(
36       FunctionType::get(Type::getVoidTy(M.getContext()), false),
37       GlobalValue::ExternalLinkage, 0, InitOrFiniKernelName, &M);
38   BasicBlock *InitOrFiniKernelBB =
39       BasicBlock::Create(M.getContext(), "", InitOrFiniKernel);
40   ReturnInst::Create(M.getContext(), InitOrFiniKernelBB);
41 
42   InitOrFiniKernel->setCallingConv(CallingConv::AMDGPU_KERNEL);
43   if (IsCtor)
44     InitOrFiniKernel->addFnAttr("device-init");
45   else
46     InitOrFiniKernel->addFnAttr("device-fini");
47   return InitOrFiniKernel;
48 }
49 
50 static bool createInitOrFiniKernel(Module &M, StringRef GlobalName,
51                                    bool IsCtor) {
52   GlobalVariable *GV = M.getGlobalVariable(GlobalName);
53   if (!GV || !GV->hasInitializer())
54     return false;
55   ConstantArray *GA = dyn_cast<ConstantArray>(GV->getInitializer());
56   if (!GA || GA->getNumOperands() == 0)
57     return false;
58 
59   Function *InitOrFiniKernel = createInitOrFiniKernelFunction(M, IsCtor);
60   IRBuilder<> IRB(InitOrFiniKernel->getEntryBlock().getTerminator());
61 
62   FunctionType *ConstructorTy = InitOrFiniKernel->getFunctionType();
63 
64   for (Value *V : GA->operands()) {
65     auto *CS = cast<ConstantStruct>(V);
66     IRB.CreateCall(ConstructorTy, CS->getOperand(1));
67   }
68 
69   appendToUsed(M, {InitOrFiniKernel});
70 
71   GV->eraseFromParent();
72   return true;
73 }
74 
75 static bool lowerCtorsAndDtors(Module &M) {
76   bool Modified = false;
77   Modified |= createInitOrFiniKernel(M, "llvm.global_ctors", /*IsCtor =*/true);
78   Modified |= createInitOrFiniKernel(M, "llvm.global_dtors", /*IsCtor =*/false);
79   return Modified;
80 }
81 
82 class AMDGPUCtorDtorLoweringLegacy final : public ModulePass {
83 public:
84   static char ID;
85   AMDGPUCtorDtorLoweringLegacy() : ModulePass(ID) {}
86   bool runOnModule(Module &M) override {
87     return lowerCtorsAndDtors(M);
88   }
89 };
90 
91 } // End anonymous namespace
92 
93 PreservedAnalyses AMDGPUCtorDtorLoweringPass::run(Module &M,
94                                                   ModuleAnalysisManager &AM) {
95   lowerCtorsAndDtors(M);
96   return PreservedAnalyses::all();
97 }
98 
99 char AMDGPUCtorDtorLoweringLegacy::ID = 0;
100 char &llvm::AMDGPUCtorDtorLoweringLegacyPassID =
101     AMDGPUCtorDtorLoweringLegacy::ID;
102 INITIALIZE_PASS(AMDGPUCtorDtorLoweringLegacy, DEBUG_TYPE,
103                 "Lower ctors and dtors for AMDGPU", false, false)
104 
105 ModulePass *llvm::createAMDGPUCtorDtorLoweringLegacyPass() {
106   return new AMDGPUCtorDtorLoweringLegacy();
107 }
108