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 11 #include "llvm/ExecutionEngine/Orc/AbsoluteSymbols.h" 12 #include "llvm/IR/BasicBlock.h" 13 #include "llvm/IR/Function.h" 14 #include "llvm/IR/IRBuilder.h" 15 #include "llvm/IR/Instruction.h" 16 #include "llvm/IR/Instructions.h" 17 #include "llvm/IR/LLVMContext.h" 18 #include "llvm/IR/Module.h" 19 #include "llvm/IR/Type.h" 20 #include "llvm/IR/Verifier.h" 21 22 namespace llvm { 23 24 namespace orc { 25 26 // ImplSymbolMap methods 27 void ImplSymbolMap::trackImpls(SymbolAliasMap ImplMaps, JITDylib *SrcJD) { 28 assert(SrcJD && "Tracking on Null Source .impl dylib"); 29 std::lock_guard<std::mutex> Lockit(ConcurrentAccess); 30 for (auto &I : ImplMaps) { 31 auto It = Maps.insert({I.first, {I.second.Aliasee, SrcJD}}); 32 // check rationale when independent dylibs have same symbol name? 33 assert(It.second && "ImplSymbols are already tracked for this Symbol?"); 34 (void)(It); 35 } 36 } 37 38 // Trigger Speculative Compiles. 39 void Speculator::speculateForEntryPoint(Speculator *Ptr, uint64_t StubId) { 40 assert(Ptr && " Null Address Received in orc_speculate_for "); 41 Ptr->speculateFor(ExecutorAddr(StubId)); 42 } 43 44 Error Speculator::addSpeculationRuntime(JITDylib &JD, 45 MangleAndInterner &Mangle) { 46 ExecutorSymbolDef ThisPtr(ExecutorAddr::fromPtr(this), 47 JITSymbolFlags::Exported); 48 ExecutorSymbolDef SpeculateForEntryPtr( 49 ExecutorAddr::fromPtr(&speculateForEntryPoint), JITSymbolFlags::Exported); 50 return JD.define(absoluteSymbols({ 51 {Mangle("__orc_speculator"), ThisPtr}, // Data Symbol 52 {Mangle("__orc_speculate_for"), SpeculateForEntryPtr} // Callable Symbol 53 })); 54 } 55 56 // If two modules, share the same LLVMContext, different threads must 57 // not access them concurrently without locking the associated LLVMContext 58 // this implementation follows this contract. 59 void IRSpeculationLayer::emit(std::unique_ptr<MaterializationResponsibility> R, 60 ThreadSafeModule TSM) { 61 62 assert(TSM && "Speculation Layer received Null Module ?"); 63 assert(TSM.getContext().getContext() != nullptr && 64 "Module with null LLVMContext?"); 65 66 // Instrumentation of runtime calls, lock the Module 67 TSM.withModuleDo([this, &R](Module &M) { 68 auto &MContext = M.getContext(); 69 auto SpeculatorVTy = StructType::create(MContext, "Class.Speculator"); 70 auto RuntimeCallTy = FunctionType::get( 71 Type::getVoidTy(MContext), 72 {PointerType::getUnqual(MContext), Type::getInt64Ty(MContext)}, false); 73 auto RuntimeCall = 74 Function::Create(RuntimeCallTy, Function::LinkageTypes::ExternalLinkage, 75 "__orc_speculate_for", &M); 76 auto SpeclAddr = new GlobalVariable( 77 M, SpeculatorVTy, false, GlobalValue::LinkageTypes::ExternalLinkage, 78 nullptr, "__orc_speculator"); 79 80 IRBuilder<> Mutator(MContext); 81 82 // QueryAnalysis allowed to transform the IR source, one such example is 83 // Simplify CFG helps the static branch prediction heuristics! 84 for (auto &Fn : M.getFunctionList()) { 85 if (!Fn.isDeclaration()) { 86 87 auto IRNames = QueryAnalysis(Fn); 88 // Instrument and register if Query has result 89 if (IRNames) { 90 91 // Emit globals for each function. 92 auto LoadValueTy = Type::getInt8Ty(MContext); 93 auto SpeculatorGuard = new GlobalVariable( 94 M, LoadValueTy, false, GlobalValue::LinkageTypes::InternalLinkage, 95 ConstantInt::get(LoadValueTy, 0), 96 "__orc_speculate.guard.for." + Fn.getName()); 97 SpeculatorGuard->setAlignment(Align(1)); 98 SpeculatorGuard->setUnnamedAddr(GlobalValue::UnnamedAddr::Local); 99 100 BasicBlock &ProgramEntry = Fn.getEntryBlock(); 101 // Create BasicBlocks before the program's entry basicblock 102 BasicBlock *SpeculateBlock = BasicBlock::Create( 103 MContext, "__orc_speculate.block", &Fn, &ProgramEntry); 104 BasicBlock *SpeculateDecisionBlock = BasicBlock::Create( 105 MContext, "__orc_speculate.decision.block", &Fn, SpeculateBlock); 106 107 assert(SpeculateDecisionBlock == &Fn.getEntryBlock() && 108 "SpeculateDecisionBlock not updated?"); 109 Mutator.SetInsertPoint(SpeculateDecisionBlock); 110 111 auto LoadGuard = 112 Mutator.CreateLoad(LoadValueTy, SpeculatorGuard, "guard.value"); 113 // if just loaded value equal to 0,return true. 114 auto CanSpeculate = 115 Mutator.CreateICmpEQ(LoadGuard, ConstantInt::get(LoadValueTy, 0), 116 "compare.to.speculate"); 117 Mutator.CreateCondBr(CanSpeculate, SpeculateBlock, &ProgramEntry); 118 119 Mutator.SetInsertPoint(SpeculateBlock); 120 auto ImplAddrToUint = 121 Mutator.CreatePtrToInt(&Fn, Type::getInt64Ty(MContext)); 122 Mutator.CreateCall(RuntimeCallTy, RuntimeCall, 123 {SpeclAddr, ImplAddrToUint}); 124 Mutator.CreateStore(ConstantInt::get(LoadValueTy, 1), 125 SpeculatorGuard); 126 Mutator.CreateBr(&ProgramEntry); 127 128 assert(Mutator.GetInsertBlock()->getParent() == &Fn && 129 "IR builder association mismatch?"); 130 S.registerSymbols(internToJITSymbols(*IRNames), 131 &R->getTargetJITDylib()); 132 } 133 } 134 } 135 }); 136 137 assert(!TSM.withModuleDo([](const Module &M) { return verifyModule(M); }) && 138 "Speculation Instrumentation breaks IR?"); 139 140 NextLayer.emit(std::move(R), std::move(TSM)); 141 } 142 143 } // namespace orc 144 } // namespace llvm 145