1 //===---------------------- EntryStage.cpp ----------------------*- C++ -*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 /// \file
10 ///
11 /// This file defines the Fetch stage of an instruction pipeline.  Its sole
12 /// purpose in life is to produce instructions for the rest of the pipeline.
13 ///
14 //===----------------------------------------------------------------------===//
15 
16 #include "llvm/MCA/Stages/EntryStage.h"
17 #include "llvm/MCA/Instruction.h"
18 
19 namespace llvm {
20 namespace mca {
21 
hasWorkToComplete() const22 bool EntryStage::hasWorkToComplete() const { return CurrentInstruction; }
23 
isAvailable(const InstRef &) const24 bool EntryStage::isAvailable(const InstRef & /* unused */) const {
25   if (CurrentInstruction)
26     return checkNextStage(CurrentInstruction);
27   return false;
28 }
29 
getNextInstruction()30 void EntryStage::getNextInstruction() {
31   assert(!CurrentInstruction && "There is already an instruction to process!");
32   if (!SM.hasNext())
33     return;
34   SourceRef SR = SM.peekNext();
35   std::unique_ptr<Instruction> Inst = llvm::make_unique<Instruction>(SR.second);
36   CurrentInstruction = InstRef(SR.first, Inst.get());
37   Instructions.emplace_back(std::move(Inst));
38   SM.updateNext();
39 }
40 
execute(InstRef &)41 llvm::Error EntryStage::execute(InstRef & /*unused */) {
42   assert(CurrentInstruction && "There is no instruction to process!");
43   if (llvm::Error Val = moveToTheNextStage(CurrentInstruction))
44     return Val;
45 
46   // Move the program counter.
47   CurrentInstruction.invalidate();
48   getNextInstruction();
49   return llvm::ErrorSuccess();
50 }
51 
cycleStart()52 llvm::Error EntryStage::cycleStart() {
53   if (!CurrentInstruction)
54     getNextInstruction();
55   return llvm::ErrorSuccess();
56 }
57 
cycleEnd()58 llvm::Error EntryStage::cycleEnd() {
59   // Find the first instruction which hasn't been retired.
60   auto Range = make_range(&Instructions[NumRetired], Instructions.end());
61   auto It = find_if(Range, [](const std::unique_ptr<Instruction> &I) {
62     return !I->isRetired();
63   });
64 
65   NumRetired = std::distance(Instructions.begin(), It);
66   // Erase instructions up to the first that hasn't been retired.
67   if ((NumRetired * 2) >= Instructions.size()) {
68     Instructions.erase(Instructions.begin(), It);
69     NumRetired = 0;
70   }
71 
72   return llvm::ErrorSuccess();
73 }
74 
75 } // namespace mca
76 } // namespace llvm
77