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/*
* Copyright (c) 2013-2014 ARM Limited
* All rights reserved
*
* The license below extends only to copyright in the software and shall
* not be construed as granting a license to any other intellectual
* property including but not limited to intellectual property relating
* to a hardware implementation of the functionality of the software
* licensed hereunder. You may use the software subject to the license
* terms below provided that you ensure that this notice is replicated
* unmodified and in its entirety in all distributions of the software,
* modified or unmodified, in source code or in binary form.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met: redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer;
* redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution;
* neither the name of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Authors: Andrew Bardsley
*/
#include "cpu/minor/decode.hh"
#include "cpu/minor/pipeline.hh"
#include "debug/Decode.hh"
namespace Minor
{
Decode::Decode(const std::string &name,
MinorCPU &cpu_,
MinorCPUParams &params,
Latch<ForwardInstData>::Output inp_,
Latch<ForwardInstData>::Input out_,
std::vector<InputBuffer<ForwardInstData>> &next_stage_input_buffer) :
Named(name),
cpu(cpu_),
inp(inp_),
out(out_),
nextStageReserve(next_stage_input_buffer),
outputWidth(params.executeInputWidth),
processMoreThanOneInput(params.decodeCycleInput),
decodeInfo(params.numThreads),
threadPriority(0)
{
if (outputWidth < 1)
fatal("%s: executeInputWidth must be >= 1 (%d)\n", name, outputWidth);
if (params.decodeInputBufferSize < 1) {
fatal("%s: decodeInputBufferSize must be >= 1 (%d)\n", name,
params.decodeInputBufferSize);
}
/* Per-thread input buffers */
for (ThreadID tid = 0; tid < params.numThreads; tid++) {
inputBuffer.push_back(
InputBuffer<ForwardInstData>(
name + ".inputBuffer" + std::to_string(tid), "insts",
params.decodeInputBufferSize));
}
}
const ForwardInstData *
Decode::getInput(ThreadID tid)
{
/* Get insts from the inputBuffer to work with */
if (!inputBuffer[tid].empty()) {
const ForwardInstData &head = inputBuffer[tid].front();
return (head.isBubble() ? NULL : &(inputBuffer[tid].front()));
} else {
return NULL;
}
}
void
Decode::popInput(ThreadID tid)
{
if (!inputBuffer[tid].empty())
inputBuffer[tid].pop();
decodeInfo[tid].inputIndex = 0;
decodeInfo[tid].inMacroop = false;
}
#if TRACING_ON
/** Add the tracing data to an instruction. This originates in
* decode because this is the first place that execSeqNums are known
* (these are used as the 'FetchSeq' in tracing data) */
static void
dynInstAddTracing(MinorDynInstPtr inst, StaticInstPtr static_inst,
MinorCPU &cpu)
{
inst->traceData = cpu.getTracer()->getInstRecord(curTick(),
cpu.getContext(inst->id.threadId),
inst->staticInst, inst->pc, static_inst);
/* Use the execSeqNum as the fetch sequence number as this most closely
* matches the other processor models' idea of fetch sequence */
if (inst->traceData)
inst->traceData->setFetchSeq(inst->id.execSeqNum);
}
#endif
void
Decode::evaluate()
{
/* Push input onto appropriate input buffer */
if (!inp.outputWire->isBubble())
inputBuffer[inp.outputWire->threadId].setTail(*inp.outputWire);
ForwardInstData &insts_out = *out.inputWire;
assert(insts_out.isBubble());
for (ThreadID tid = 0; tid < cpu.numThreads; tid++)
decodeInfo[tid].blocked = !nextStageReserve[tid].canReserve();
ThreadID tid = getScheduledThread();
if (tid != InvalidThreadID) {
DecodeThreadInfo &decode_info = decodeInfo[tid];
const ForwardInstData *insts_in = getInput(tid);
unsigned int output_index = 0;
/* Pack instructions into the output while we can. This may involve
* using more than one input line */
while (insts_in &&
decode_info.inputIndex < insts_in->width() && /* Still more input */
output_index < outputWidth /* Still more output to fill */)
{
MinorDynInstPtr inst = insts_in->insts[decode_info.inputIndex];
if (inst->isBubble()) {
/* Skip */
decode_info.inputIndex++;
decode_info.inMacroop = false;
} else {
StaticInstPtr static_inst = inst->staticInst;
/* Static inst of a macro-op above the output_inst */
StaticInstPtr parent_static_inst = NULL;
MinorDynInstPtr output_inst = inst;
if (inst->isFault()) {
DPRINTF(Decode, "Fault being passed: %d\n",
inst->fault->name());
decode_info.inputIndex++;
decode_info.inMacroop = false;
} else if (static_inst->isMacroop()) {
/* Generate a new micro-op */
StaticInstPtr static_micro_inst;
/* Set up PC for the next micro-op emitted */
if (!decode_info.inMacroop) {
decode_info.microopPC = inst->pc;
decode_info.inMacroop = true;
}
/* Get the micro-op static instruction from the
* static_inst. */
static_micro_inst =
static_inst->fetchMicroop(
decode_info.microopPC.microPC());
output_inst = new MinorDynInst(inst->id);
output_inst->pc = decode_info.microopPC;
output_inst->staticInst = static_micro_inst;
output_inst->fault = NoFault;
/* Allow a predicted next address only on the last
* microop */
if (static_micro_inst->isLastMicroop()) {
output_inst->predictedTaken = inst->predictedTaken;
output_inst->predictedTarget = inst->predictedTarget;
}
DPRINTF(Decode, "Microop decomposition inputIndex:"
" %d output_index: %d lastMicroop: %s microopPC:"
" %d.%d inst: %d\n",
decode_info.inputIndex, output_index,
(static_micro_inst->isLastMicroop() ?
"true" : "false"),
decode_info.microopPC.instAddr(),
decode_info.microopPC.microPC(),
*output_inst);
/* Acknowledge that the static_inst isn't mine, it's my
* parent macro-op's */
parent_static_inst = static_inst;
static_micro_inst->advancePC(decode_info.microopPC);
/* Step input if this is the last micro-op */
if (static_micro_inst->isLastMicroop()) {
decode_info.inputIndex++;
decode_info.inMacroop = false;
}
} else {
/* Doesn't need decomposing, pass on instruction */
DPRINTF(Decode, "Passing on inst: %s inputIndex:"
" %d output_index: %d\n",
*output_inst, decode_info.inputIndex, output_index);
parent_static_inst = static_inst;
/* Step input */
decode_info.inputIndex++;
decode_info.inMacroop = false;
}
/* Set execSeqNum of output_inst */
output_inst->id.execSeqNum = decode_info.execSeqNum;
/* Add tracing */
#if TRACING_ON
dynInstAddTracing(output_inst, parent_static_inst, cpu);
#endif
/* Step to next sequence number */
decode_info.execSeqNum++;
/* Correctly size the output before writing */
if (output_index == 0) insts_out.resize(outputWidth);
/* Push into output */
insts_out.insts[output_index] = output_inst;
output_index++;
}
/* Have we finished with the input? */
if (decode_info.inputIndex == insts_in->width()) {
/* If we have just been producing micro-ops, we *must* have
* got to the end of that for inputIndex to be pushed past
* insts_in->width() */
assert(!decode_info.inMacroop);
popInput(tid);
insts_in = NULL;
if (processMoreThanOneInput) {
DPRINTF(Decode, "Wrapping\n");
insts_in = getInput(tid);
}
}
}
/* The rest of the output (if any) should already have been packed
* with bubble instructions by insts_out's initialisation
*
* for (; output_index < outputWidth; output_index++)
* assert(insts_out.insts[output_index]->isBubble());
*/
}
/* If we generated output, reserve space for the result in the next stage
* and mark the stage as being active this cycle */
if (!insts_out.isBubble()) {
/* Note activity of following buffer */
cpu.activityRecorder->activity();
insts_out.threadId = tid;
nextStageReserve[tid].reserve();
}
/* If we still have input to process and somewhere to put it,
* mark stage as active */
for (ThreadID i = 0; i < cpu.numThreads; i++)
{
if (getInput(i) && nextStageReserve[i].canReserve()) {
cpu.activityRecorder->activateStage(Pipeline::DecodeStageId);
break;
}
}
/* Make sure the input (if any left) is pushed */
if (!inp.outputWire->isBubble())
inputBuffer[inp.outputWire->threadId].pushTail();
}
inline ThreadID
Decode::getScheduledThread()
{
/* Select thread via policy. */
std::vector<ThreadID> priority_list;
switch (cpu.threadPolicy) {
case Enums::SingleThreaded:
priority_list.push_back(0);
break;
case Enums::RoundRobin:
priority_list = cpu.roundRobinPriority(threadPriority);
break;
case Enums::Random:
priority_list = cpu.randomPriority();
break;
default:
panic("Unknown fetch policy");
}
for (auto tid : priority_list) {
if (getInput(tid) && !decodeInfo[tid].blocked) {
threadPriority = tid;
return tid;
}
}
return InvalidThreadID;
}
bool
Decode::isDrained()
{
for (const auto &buffer : inputBuffer) {
if (!buffer.empty())
return false;
}
return (*inp.outputWire).isBubble();
}
void
Decode::minorTrace() const
{
std::ostringstream data;
if (decodeInfo[0].blocked)
data << 'B';
else
(*out.inputWire).reportData(data);
MINORTRACE("insts=%s\n", data.str());
inputBuffer[0].minorTrace();
}
}