1 //===-- NVPTXCtorDtorLowering.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 "NVPTXCtorDtorLowering.h" 14 #include "NVPTX.h" 15 #include "llvm/ADT/StringExtras.h" 16 #include "llvm/IR/Constants.h" 17 #include "llvm/IR/Function.h" 18 #include "llvm/IR/GlobalVariable.h" 19 #include "llvm/IR/IRBuilder.h" 20 #include "llvm/IR/Module.h" 21 #include "llvm/IR/Value.h" 22 #include "llvm/Pass.h" 23 #include "llvm/Support/CommandLine.h" 24 #include "llvm/Transforms/Utils/ModuleUtils.h" 25 26 using namespace llvm; 27 28 #define DEBUG_TYPE "nvptx-lower-ctor-dtor" 29 30 static cl::opt<std::string> 31 GlobalStr("nvptx-lower-global-ctor-dtor-id", 32 cl::desc("Override unique ID of ctor/dtor globals."), 33 cl::init(""), cl::Hidden); 34 35 namespace { 36 37 static std::string getHash(StringRef Str) { 38 llvm::MD5 Hasher; 39 llvm::MD5::MD5Result Hash; 40 Hasher.update(Str); 41 Hasher.final(Hash); 42 return llvm::utohexstr(Hash.low(), /*LowerCase=*/true); 43 } 44 45 static bool createInitOrFiniGlobls(Module &M, StringRef GlobalName, 46 bool IsCtor) { 47 GlobalVariable *GV = M.getGlobalVariable(GlobalName); 48 if (!GV || !GV->hasInitializer()) 49 return false; 50 ConstantArray *GA = dyn_cast<ConstantArray>(GV->getInitializer()); 51 if (!GA || GA->getNumOperands() == 0) 52 return false; 53 54 // NVPTX has no way to emit variables at specific sections or support for 55 // the traditional constructor sections. Instead, we emit mangled global 56 // names so the runtime can build the list manually. 57 for (Value *V : GA->operands()) { 58 auto *CS = cast<ConstantStruct>(V); 59 auto *F = cast<Constant>(CS->getOperand(1)); 60 uint64_t Priority = cast<ConstantInt>(CS->getOperand(0))->getSExtValue(); 61 std::string PriorityStr = "." + std::to_string(Priority); 62 // We append a semi-unique hash and the priority to the global name. 63 std::string GlobalID = 64 !GlobalStr.empty() ? GlobalStr : getHash(M.getSourceFileName()); 65 std::string NameStr = 66 ((IsCtor ? "__init_array_object_" : "__fini_array_object_") + 67 F->getName() + "_" + GlobalID + "_" + std::to_string(Priority)) 68 .str(); 69 // PTX does not support exported names with '.' in them. 70 llvm::transform(NameStr, NameStr.begin(), 71 [](char c) { return c == '.' ? '_' : c; }); 72 73 auto *GV = new GlobalVariable(M, F->getType(), /*IsConstant=*/true, 74 GlobalValue::ExternalLinkage, F, NameStr, 75 nullptr, GlobalValue::NotThreadLocal, 76 /*AddressSpace=*/4); 77 // This isn't respected by Nvidia, simply put here for clarity. 78 GV->setSection(IsCtor ? ".init_array" + PriorityStr 79 : ".fini_array" + PriorityStr); 80 GV->setVisibility(GlobalVariable::ProtectedVisibility); 81 appendToUsed(M, {GV}); 82 } 83 84 GV->eraseFromParent(); 85 return true; 86 } 87 88 static bool lowerCtorsAndDtors(Module &M) { 89 bool Modified = false; 90 Modified |= createInitOrFiniGlobls(M, "llvm.global_ctors", /*IsCtor =*/true); 91 Modified |= createInitOrFiniGlobls(M, "llvm.global_dtors", /*IsCtor =*/false); 92 return Modified; 93 } 94 95 class NVPTXCtorDtorLoweringLegacy final : public ModulePass { 96 public: 97 static char ID; 98 NVPTXCtorDtorLoweringLegacy() : ModulePass(ID) {} 99 bool runOnModule(Module &M) override { return lowerCtorsAndDtors(M); } 100 }; 101 102 } // End anonymous namespace 103 104 PreservedAnalyses NVPTXCtorDtorLoweringPass::run(Module &M, 105 ModuleAnalysisManager &AM) { 106 return lowerCtorsAndDtors(M) ? PreservedAnalyses::none() 107 : PreservedAnalyses::all(); 108 } 109 110 char NVPTXCtorDtorLoweringLegacy::ID = 0; 111 char &llvm::NVPTXCtorDtorLoweringLegacyPassID = NVPTXCtorDtorLoweringLegacy::ID; 112 INITIALIZE_PASS(NVPTXCtorDtorLoweringLegacy, DEBUG_TYPE, 113 "Lower ctors and dtors for NVPTX", false, false) 114 115 ModulePass *llvm::createNVPTXCtorDtorLoweringLegacyPass() { 116 return new NVPTXCtorDtorLoweringLegacy(); 117 } 118