EntryStage.cpp revision 360784 
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
18namespace llvm {
19namespace mca {
20
21bool EntryStage::hasWorkToComplete() const {
22  return static_cast<bool>(CurrentInstruction);
23}
24
25bool EntryStage::isAvailable(const InstRef & /* unused */) const {
26  if (CurrentInstruction)
27    return checkNextStage(CurrentInstruction);
28  return false;
29}
30
31void EntryStage::getNextInstruction() {
32  assert(!CurrentInstruction && "There is already an instruction to process!");
33  if (!SM.hasNext())
34    return;
35  SourceRef SR = SM.peekNext();
36  std::unique_ptr<Instruction> Inst = std::make_unique<Instruction>(SR.second);
37  CurrentInstruction = InstRef(SR.first, Inst.get());
38  Instructions.emplace_back(std::move(Inst));
39  SM.updateNext();
40}
41
42llvm::Error EntryStage::execute(InstRef & /*unused */) {
43  assert(CurrentInstruction && "There is no instruction to process!");
44  if (llvm::Error Val = moveToTheNextStage(CurrentInstruction))
45    return Val;
46
47  // Move the program counter.
48  CurrentInstruction.invalidate();
49  getNextInstruction();
50  return llvm::ErrorSuccess();
51}
52
53llvm::Error EntryStage::cycleStart() {
54  if (!CurrentInstruction)
55    getNextInstruction();
56  return llvm::ErrorSuccess();
57}
58
59llvm::Error EntryStage::cycleEnd() {
60  // Find the first instruction which hasn't been retired.
61  auto Range = make_range(&Instructions[NumRetired], Instructions.end());
62  auto It = find_if(Range, [](const std::unique_ptr<Instruction> &I) {
63    return !I->isRetired();
64  });
65
66  NumRetired = std::distance(Instructions.begin(), It);
67  // Erase instructions up to the first that hasn't been retired.
68  if ((NumRetired * 2) >= Instructions.size()) {
69    Instructions.erase(Instructions.begin(), It);
70    NumRetired = 0;
71  }
72
73  return llvm::ErrorSuccess();
74}
75
76} // namespace mca
77} // namespace llvm
78