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cpu: Modernise the branch predictor (STL and C++11)

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This patch does some minor house keeping of the branch predictor by
adopting STL containers, and shifting some iterator to use range-based
for loops.

The predictor history is also changed from a list to a deque as we
never to insertion/deletion other than at the front and back.
This commit is contained in:
Andreas Hansson 2014-08-13 06:57:21 -04:00
parent 94daae6864
commit 66904b9584
2 changed files with 21 additions and 25 deletions
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11
src/cpu/pred/bpred_unit.hh
View file

@ -1,5 +1,5 @@
/*
* Copyright (c) 2011-2012 ARM Limited
* Copyright (c) 2011-2012, 2014 ARM Limited
* Copyright (c) 2010 The University of Edinburgh
* All rights reserved
*
@ -47,7 +47,7 @@
#ifndef __CPU_PRED_BPRED_UNIT_HH__
#define __CPU_PRED_BPRED_UNIT_HH__
#include <list>
#include <deque>
#include "base/statistics.hh"
#include "base/types.hh"
@ -244,8 +244,7 @@ class BPredUnit : public SimObject
bool wasReturn;
};
typedef std::list<PredictorHistory> History;
typedef History::iterator HistoryIt;
typedef std::deque<PredictorHistory> History;
/** Number of the threads for which the branch history is maintained. */
uint32_t numThreads;
@ -255,13 +254,13 @@ class BPredUnit : public SimObject
* as instructions are committed, or restore it to the proper state after
* a squash.
*/
History *predHist;
std::vector<History> predHist;
/** The BTB. */
DefaultBTB BTB;
/** The per-thread return address stack. */
ReturnAddrStack *RAS;
std::vector<ReturnAddrStack> RAS;
/** Stat for number of BP lookups. */
Stats::Scalar lookups;

35
src/cpu/pred/bpred_unit_impl.hh
View file

@ -1,5 +1,5 @@
/*
* Copyright (c) 2011-2012 ARM Limited
* Copyright (c) 2011-2012, 2014 ARM Limited
* Copyright (c) 2010 The University of Edinburgh
* Copyright (c) 2012 Mark D. Hill and David A. Wood
* All rights reserved
@ -57,17 +57,15 @@
BPredUnit::BPredUnit(const Params *params)
: SimObject(params),
numThreads(params->numThreads),
predHist(numThreads),
BTB(params->BTBEntries,
params->BTBTagSize,
params->instShiftAmt)
params->instShiftAmt),
RAS(numThreads)
{
numThreads = params->numThreads;
predHist = new History[numThreads];
RAS = new ReturnAddrStack[numThreads];
for (int i=0; i < numThreads; i++)
RAS[i].init(params->RASSize);
for (auto& r : RAS)
r.init(params->RASSize);
}
void
@ -126,8 +124,8 @@ BPredUnit::drainSanityCheck() const
{
// We shouldn't have any outstanding requests when we resume from
// a drained system.
for (int i = 0; i < numThreads; ++i)
assert(predHist[i].empty());
for (const auto& ph M5_VAR_USED : predHist)
assert(ph.empty());
}
bool
@ -448,7 +446,7 @@ BPredUnit::squash(const InstSeqNum &squashed_sn,
// fix up the entry.
if (!pred_hist.empty()) {
HistoryIt hist_it = pred_hist.begin();
auto hist_it = pred_hist.begin();
//HistoryIt hist_it = find(pred_hist.begin(), pred_hist.end(),
// squashed_sn);
@ -516,15 +514,14 @@ BPredUnit::squash(const InstSeqNum &squashed_sn,
void
BPredUnit::dump()
{
HistoryIt pred_hist_it;
int i = 0;
for (const auto& ph : predHist) {
if (!ph.empty()) {
auto pred_hist_it = ph.begin();
for (int i = 0; i < numThreads; ++i) {
if (!predHist[i].empty()) {
pred_hist_it = predHist[i].begin();
cprintf("predHist[%i].size(): %i\n", i++, ph.size());
cprintf("predHist[%i].size(): %i\n", i, predHist[i].size());
while (pred_hist_it != predHist[i].end()) {
while (pred_hist_it != ph.end()) {
cprintf("[sn:%lli], PC:%#x, tid:%i, predTaken:%i, "
"bpHistory:%#x\n",
pred_hist_it->seqNum, pred_hist_it->pc,