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| author | Rekai Gonzalez-Alberquilla <rekai.gonzalezalberquilla@arm.com> | 2017-02-06 11:10:06 +0000 |
|---|---|---|
| committer | Giacomo Gabrielli <giacomo.gabrielli@arm.com> | 2018-11-16 10:39:03 +0000 |
| commit | 0c50a0b4fe3956f9d2e08e75d47c9cbd79bf0268 (patch) | |
| tree | 7679abe2343e0504c93eb73d09635d546a211455 /src/cpu/o3/fetch_impl.hh | |
| parent | 338a173e822298bd22741342a7b24352450afdd1 (diff) | |
| download | gem5-0c50a0b4fe3956f9d2e08e75d47c9cbd79bf0268.tar.xz | |
cpu: Fix the usage of const DynInstPtr
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>
Diffstat (limited to 'src/cpu/o3/fetch_impl.hh')
| -rw-r--r-- | src/cpu/o3/fetch_impl.hh | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/src/cpu/o3/fetch_impl.hh b/src/cpu/o3/fetch_impl.hh index 2df7b84ee..5810c032f 100644 --- a/src/cpu/o3/fetch_impl.hh +++ b/src/cpu/o3/fetch_impl.hh @@ -546,7 +546,7 @@ DefaultFetch<Impl>::deactivateThread(ThreadID tid) template <class Impl> bool DefaultFetch<Impl>::lookupAndUpdateNextPC( - DynInstPtr &inst, TheISA::PCState &nextPC) + const DynInstPtr &inst, TheISA::PCState &nextPC) { // Do branch prediction check here. // A bit of a misnomer...next_PC is actually the current PC until @@ -953,7 +953,7 @@ DefaultFetch<Impl>::tick() while (available_insts != 0 && insts_to_decode < decodeWidth) { ThreadID tid = *tid_itr; if (!stalls[tid].decode && !fetchQueue[tid].empty()) { - auto inst = fetchQueue[tid].front(); + const auto& inst = fetchQueue[tid].front(); toDecode->insts[toDecode->size++] = inst; DPRINTF(Fetch, "[tid:%i][sn:%i]: Sending instruction to decode from " "fetch queue. Fetch queue size: %i.\n", |