1 //===---------- speculation.cpp - Utilities for Speculation ----------===// 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 #include "llvm/ExecutionEngine/Orc/Speculation.h" 10 #include "llvm/IR/BasicBlock.h" 11 #include "llvm/IR/Function.h" 12 #include "llvm/IR/IRBuilder.h" 13 #include "llvm/IR/Instruction.h" 14 #include "llvm/IR/Instructions.h" 15 #include "llvm/IR/LLVMContext.h" 16 #include "llvm/IR/Module.h" 17 #include "llvm/IR/Type.h" 18 #include "llvm/IR/Verifier.h" 19 20 namespace llvm { 21 22 namespace orc { 23 24 // ImplSymbolMap methods 25 void ImplSymbolMap::trackImpls(SymbolAliasMap ImplMaps, JITDylib *SrcJD) { 26 assert(SrcJD && "Tracking on Null Source .impl dylib"); 27 std::lock_guard<std::mutex> Lockit(ConcurrentAccess); 28 for (auto &I : ImplMaps) { 29 auto It = Maps.insert({I.first, {I.second.Aliasee, SrcJD}}); 30 // check rationale when independent dylibs have same symbol name? 31 assert(It.second && "ImplSymbols are already tracked for this Symbol?"); 32 (void)(It); 33 } 34 } 35 36 // Trigger Speculative Compiles. 37 void Speculator::speculateForEntryPoint(Speculator *Ptr, uint64_t StubId) { 38 assert(Ptr && " Null Address Received in orc_speculate_for "); 39 Ptr->speculateFor(StubId); 40 } 41 42 Error Speculator::addSpeculationRuntime(JITDylib &JD, 43 MangleAndInterner &Mangle) { 44 JITEvaluatedSymbol ThisPtr(pointerToJITTargetAddress(this), 45 JITSymbolFlags::Exported); 46 JITEvaluatedSymbol SpeculateForEntryPtr( 47 pointerToJITTargetAddress(&speculateForEntryPoint), 48 JITSymbolFlags::Exported); 49 return JD.define(absoluteSymbols({ 50 {Mangle("__orc_speculator"), ThisPtr}, // Data Symbol 51 {Mangle("__orc_speculate_for"), SpeculateForEntryPtr} // Callable Symbol 52 })); 53 } 54 55 // If two modules, share the same LLVMContext, different threads must 56 // not access them concurrently without locking the associated LLVMContext 57 // this implementation follows this contract. 58 void IRSpeculationLayer::emit(std::unique_ptr<MaterializationResponsibility> R, 59 ThreadSafeModule TSM) { 60 61 assert(TSM && "Speculation Layer received Null Module ?"); 62 assert(TSM.getContext().getContext() != nullptr && 63 "Module with null LLVMContext?"); 64 65 // Instrumentation of runtime calls, lock the Module 66 TSM.withModuleDo([this, &R](Module &M) { 67 auto &MContext = M.getContext(); 68 auto SpeculatorVTy = StructType::create(MContext, "Class.Speculator"); 69 auto RuntimeCallTy = FunctionType::get( 70 Type::getVoidTy(MContext), 71 {SpeculatorVTy->getPointerTo(), Type::getInt64Ty(MContext)}, false); 72 auto RuntimeCall = 73 Function::Create(RuntimeCallTy, Function::LinkageTypes::ExternalLinkage, 74 "__orc_speculate_for", &M); 75 auto SpeclAddr = new GlobalVariable( 76 M, SpeculatorVTy, false, GlobalValue::LinkageTypes::ExternalLinkage, 77 nullptr, "__orc_speculator"); 78 79 IRBuilder<> Mutator(MContext); 80 81 // QueryAnalysis allowed to transform the IR source, one such example is 82 // Simplify CFG helps the static branch prediction heuristics! 83 for (auto &Fn : M.getFunctionList()) { 84 if (!Fn.isDeclaration()) { 85 86 auto IRNames = QueryAnalysis(Fn); 87 // Instrument and register if Query has result 88 if (IRNames.hasValue()) { 89 90 // Emit globals for each function. 91 auto LoadValueTy = Type::getInt8Ty(MContext); 92 auto SpeculatorGuard = new GlobalVariable( 93 M, LoadValueTy, false, GlobalValue::LinkageTypes::InternalLinkage, 94 ConstantInt::get(LoadValueTy, 0), 95 "__orc_speculate.guard.for." + Fn.getName()); 96 SpeculatorGuard->setAlignment(Align(1)); 97 SpeculatorGuard->setUnnamedAddr(GlobalValue::UnnamedAddr::Local); 98 99 BasicBlock &ProgramEntry = Fn.getEntryBlock(); 100 // Create BasicBlocks before the program's entry basicblock 101 BasicBlock *SpeculateBlock = BasicBlock::Create( 102 MContext, "__orc_speculate.block", &Fn, &ProgramEntry); 103 BasicBlock *SpeculateDecisionBlock = BasicBlock::Create( 104 MContext, "__orc_speculate.decision.block", &Fn, SpeculateBlock); 105 106 assert(SpeculateDecisionBlock == &Fn.getEntryBlock() && 107 "SpeculateDecisionBlock not updated?"); 108 Mutator.SetInsertPoint(SpeculateDecisionBlock); 109 110 auto LoadGuard = 111 Mutator.CreateLoad(LoadValueTy, SpeculatorGuard, "guard.value"); 112 // if just loaded value equal to 0,return true. 113 auto CanSpeculate = 114 Mutator.CreateICmpEQ(LoadGuard, ConstantInt::get(LoadValueTy, 0), 115 "compare.to.speculate"); 116 Mutator.CreateCondBr(CanSpeculate, SpeculateBlock, &ProgramEntry); 117 118 Mutator.SetInsertPoint(SpeculateBlock); 119 auto ImplAddrToUint = 120 Mutator.CreatePtrToInt(&Fn, Type::getInt64Ty(MContext)); 121 Mutator.CreateCall(RuntimeCallTy, RuntimeCall, 122 {SpeclAddr, ImplAddrToUint}); 123 Mutator.CreateStore(ConstantInt::get(LoadValueTy, 1), 124 SpeculatorGuard); 125 Mutator.CreateBr(&ProgramEntry); 126 127 assert(Mutator.GetInsertBlock()->getParent() == &Fn && 128 "IR builder association mismatch?"); 129 S.registerSymbols(internToJITSymbols(IRNames.getValue()), 130 &R->getTargetJITDylib()); 131 } 132 } 133 } 134 }); 135 136 assert(!TSM.withModuleDo([](const Module &M) { return verifyModule(M); }) && 137 "Speculation Instrumentation breaks IR?"); 138 139 NextLayer.emit(std::move(R), std::move(TSM)); 140 } 141 142 } // namespace orc 143 } // namespace llvm 144