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//===---------------------- RetireControlUnit.cpp ---------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
/// \file
///
/// This file simulates the hardware responsible for retiring instructions.
///
//===----------------------------------------------------------------------===//
#include "llvm/MCA/HardwareUnits/RetireControlUnit.h"
#include "llvm/Support/Debug.h"
#define DEBUG_TYPE "llvm-mca"
namespace llvm {
namespace mca {
RetireControlUnit::RetireControlUnit(const MCSchedModel &SM)
: NextAvailableSlotIdx(0), CurrentInstructionSlotIdx(0),
AvailableEntries(SM.isOutOfOrder() ? SM.MicroOpBufferSize : 0),
MaxRetirePerCycle(0) {
// Check if the scheduling model provides extra information about the machine
// processor. If so, then use that information to set the reorder buffer size
// and the maximum number of instructions retired per cycle.
if (SM.hasExtraProcessorInfo()) {
const MCExtraProcessorInfo &EPI = SM.getExtraProcessorInfo();
if (EPI.ReorderBufferSize)
AvailableEntries = EPI.ReorderBufferSize;
MaxRetirePerCycle = EPI.MaxRetirePerCycle;
}
NumROBEntries = AvailableEntries;
if (!SM.isOutOfOrder() && !NumROBEntries)
return;
assert(NumROBEntries && "Invalid reorder buffer size!");
Queue.resize(2 * NumROBEntries);
}
// Reserves a number of slots, and returns a new token.
unsigned RetireControlUnit::dispatch(const InstRef &IR) {
if (!NumROBEntries)
return UnhandledTokenID;
const Instruction &Inst = *IR.getInstruction();
unsigned Entries = normalizeQuantity(Inst.getNumMicroOps());
assert((AvailableEntries >= Entries) && "Reorder Buffer unavailable!");
unsigned TokenID = NextAvailableSlotIdx;
Queue[NextAvailableSlotIdx] = {IR, Entries, false};
NextAvailableSlotIdx += std::max(1U, Entries);
NextAvailableSlotIdx %= Queue.size();
assert(TokenID < UnhandledTokenID && "Invalid token ID");
AvailableEntries -= Entries;
return TokenID;
}
const RetireControlUnit::RUToken &RetireControlUnit::getCurrentToken() const {
const RetireControlUnit::RUToken &Current = Queue[CurrentInstructionSlotIdx];
#ifndef NDEBUG
const Instruction *Inst = Current.IR.getInstruction();
assert(Inst && "Invalid RUToken in the RCU queue.");
#endif
return Current;
}
unsigned RetireControlUnit::computeNextSlotIdx() const {
const RetireControlUnit::RUToken &Current = getCurrentToken();
unsigned NextSlotIdx = CurrentInstructionSlotIdx + std::max(1U, Current.NumSlots);
return NextSlotIdx % Queue.size();
}
const RetireControlUnit::RUToken &RetireControlUnit::peekNextToken() const {
return Queue[computeNextSlotIdx()];
}
void RetireControlUnit::consumeCurrentToken() {
RetireControlUnit::RUToken &Current = Queue[CurrentInstructionSlotIdx];
Current.IR.getInstruction()->retire();
// Update the slot index to be the next item in the circular queue.
CurrentInstructionSlotIdx += std::max(1U, Current.NumSlots);
CurrentInstructionSlotIdx %= Queue.size();
AvailableEntries += Current.NumSlots;
Current = { InstRef(), 0U, false };
}
void RetireControlUnit::onInstructionExecuted(unsigned TokenID) {
assert(Queue.size() > TokenID);
assert(Queue[TokenID].IR.getInstruction() && "Instruction was not dispatched!");
assert(Queue[TokenID].Executed == false && "Instruction already executed!");
Queue[TokenID].Executed = true;
}
#ifndef NDEBUG
void RetireControlUnit::dump() const {
dbgs() << "Retire Unit: { Total ROB Entries =" << NumROBEntries
<< ", Available ROB entries=" << AvailableEntries << " }\n";
}
#endif
} // namespace mca
} // namespace llvm
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