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cpu: Fix the usage of const DynInstPtr

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Summary: Usage of const DynInstPtr& when possible and introduction of
move operators to RefCountingPtr.

In many places, scoped references to dynamic instructions do a copy of
the DynInstPtr when a reference would do. This is detrimental to
performance. On top of that, in case there is a need for reference
tracking for debugging, the redundant copies make the process much more
painful than it already is.

Also, from the theoretical point of view, a function/method that
defines a convenience name to access an instruction should not be
considered an owner of the data, i.e., doing a copy and not a reference
is not justified.

On a related topic, C++11 introduces move semantics, and those are
useful when, for example, there is a class modelling a HW structure that
contains a list, and has a getHeadOfList function, to prevent doing a
copy to an internal variable -> update pointer, remove from the list ->
update pointer, return value making a copy to the assined variable ->
update pointer, destroy the returned value -> update pointer.

Change-Id: I3bb46c20ef23b6873b469fd22befb251ac44d2f6
Signed-off-by: Giacomo Gabrielli <giacomo.gabrielli@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/13105
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>
This commit is contained in:
Rekai Gonzalez-Alberquilla
2017-02-06 11:10:06 +00:00
committed by Giacomo Gabrielli
parent 338a173e82
commit 0c50a0b4fe
36 changed files with 274 additions and 210 deletions
Download Patch File Download Diff File Expand all files Collapse all files

16
src/cpu/o3/commit_impl.hh
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@@ -636,7 +636,7 @@ DefaultCommit<Impl>::squashFromSquashAfter(ThreadID tid)
template <class Impl>
void
DefaultCommit<Impl>::squashAfter(ThreadID tid, DynInstPtr &head_inst)
DefaultCommit<Impl>::squashAfter(ThreadID tid, const DynInstPtr &head_inst)
{
DPRINTF(Commit, "Executing squash after for [tid:%i] inst [sn:%lli]\n",
tid, head_inst->seqNum);
@@ -696,14 +696,14 @@ DefaultCommit<Impl>::tick()
// will be active.
_nextStatus = Active;
DynInstPtr inst = rob->readHeadInst(tid);
const DynInstPtr &inst M5_VAR_USED = rob->readHeadInst(tid);
DPRINTF(Commit,"[tid:%i]: Instruction [sn:%lli] PC %s is head of"
" ROB and ready to commit\n",
tid, inst->seqNum, inst->pcState());
} else if (!rob->isEmpty(tid)) {
DynInstPtr inst = rob->readHeadInst(tid);
const DynInstPtr &inst = rob->readHeadInst(tid);
ppCommitStall->notify(inst);
@@ -1136,7 +1136,7 @@ DefaultCommit<Impl>::commitInsts()
template <class Impl>
bool
DefaultCommit<Impl>::commitHead(DynInstPtr &head_inst, unsigned inst_num)
DefaultCommit<Impl>::commitHead(const DynInstPtr &head_inst, unsigned inst_num)
{
assert(head_inst);
@@ -1317,9 +1317,7 @@ DefaultCommit<Impl>::getInsts()
int insts_to_process = std::min((int)renameWidth, fromRename->size);
for (int inst_num = 0; inst_num < insts_to_process; ++inst_num) {
DynInstPtr inst;
inst = fromRename->insts[inst_num];
const DynInstPtr &inst = fromRename->insts[inst_num];
ThreadID tid = inst->threadNumber;
if (!inst->isSquashed() &&
@@ -1366,7 +1364,7 @@ DefaultCommit<Impl>::markCompletedInsts()
template <class Impl>
void
DefaultCommit<Impl>::updateComInstStats(DynInstPtr &inst)
DefaultCommit<Impl>::updateComInstStats(const DynInstPtr &inst)
{
ThreadID tid = inst->threadNumber;
@@ -1507,7 +1505,7 @@ DefaultCommit<Impl>::oldestReady()
if (rob->isHeadReady(tid)) {
DynInstPtr head_inst = rob->readHeadInst(tid);
const DynInstPtr &head_inst = rob->readHeadInst(tid);
if (first) {
oldest = tid;