1 //===---------------------- EntryStage.cpp ----------------------*- C++ -*-===// 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 /// \file 9 /// 10 /// This file defines the Fetch stage of an instruction pipeline. Its sole 11 /// purpose in life is to produce instructions for the rest of the pipeline. 12 /// 13 //===----------------------------------------------------------------------===// 14 15 #include "llvm/MCA/Stages/EntryStage.h" 16 #include "llvm/MCA/Instruction.h" 17 18 namespace llvm { 19 namespace mca { 20 21 bool EntryStage::hasWorkToComplete() const { 22 return static_cast<bool>(CurrentInstruction) || !SM.isEnd(); 23 } 24 25 bool EntryStage::isAvailable(const InstRef & /* unused */) const { 26 if (CurrentInstruction) 27 return checkNextStage(CurrentInstruction); 28 return false; 29 } 30 31 Error EntryStage::getNextInstruction() { 32 assert(!CurrentInstruction && "There is already an instruction to process!"); 33 if (!SM.hasNext()) { 34 if (!SM.isEnd()) 35 return llvm::make_error<InstStreamPause>(); 36 else 37 return llvm::ErrorSuccess(); 38 } 39 SourceRef SR = SM.peekNext(); 40 std::unique_ptr<Instruction> Inst = std::make_unique<Instruction>(SR.second); 41 CurrentInstruction = InstRef(SR.first, Inst.get()); 42 Instructions.emplace_back(std::move(Inst)); 43 SM.updateNext(); 44 return llvm::ErrorSuccess(); 45 } 46 47 llvm::Error EntryStage::execute(InstRef & /*unused */) { 48 assert(CurrentInstruction && "There is no instruction to process!"); 49 if (llvm::Error Val = moveToTheNextStage(CurrentInstruction)) 50 return Val; 51 52 // Move the program counter. 53 CurrentInstruction.invalidate(); 54 return getNextInstruction(); 55 } 56 57 llvm::Error EntryStage::cycleStart() { 58 if (!CurrentInstruction) 59 return getNextInstruction(); 60 return llvm::ErrorSuccess(); 61 } 62 63 llvm::Error EntryStage::cycleResume() { 64 assert(!CurrentInstruction); 65 return getNextInstruction(); 66 } 67 68 llvm::Error EntryStage::cycleEnd() { 69 // Find the first instruction which hasn't been retired. 70 auto Range = 71 make_range(Instructions.begin() + NumRetired, Instructions.end()); 72 auto It = find_if(Range, [](const std::unique_ptr<Instruction> &I) { 73 return !I->isRetired(); 74 }); 75 76 NumRetired = std::distance(Instructions.begin(), It); 77 // Erase instructions up to the first that hasn't been retired. 78 if ((NumRetired * 2) >= Instructions.size()) { 79 Instructions.erase(Instructions.begin(), It); 80 NumRetired = 0; 81 } 82 83 return llvm::ErrorSuccess(); 84 } 85 86 } // namespace mca 87 } // namespace llvm 88