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