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