From 0c50a0b4fe3956f9d2e08e75d47c9cbd79bf0268 Mon Sep 17 00:00:00 2001
From: Rekai Gonzalez-Alberquilla <rekai.gonzalezalberquilla@arm.com>
Date: Mon, 6 Feb 2017 11:10:06 +0000
Subject: 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>
---
 src/cpu/o3/iew_impl.hh | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

(limited to 'src/cpu/o3/iew_impl.hh')

diff --git a/src/cpu/o3/iew_impl.hh b/src/cpu/o3/iew_impl.hh
index 8270a71b5..e46bc5ba5 100644
--- a/src/cpu/o3/iew_impl.hh
+++ b/src/cpu/o3/iew_impl.hh
@@ -478,7 +478,7 @@ DefaultIEW<Impl>::squash(ThreadID tid)
 
 template<class Impl>
 void
-DefaultIEW<Impl>::squashDueToBranch(DynInstPtr &inst, ThreadID tid)
+DefaultIEW<Impl>::squashDueToBranch(const DynInstPtr& inst, ThreadID tid)
 {
     DPRINTF(IEW, "[tid:%i]: Squashing from a specific instruction, PC: %s "
             "[sn:%i].\n", tid, inst->pcState(), inst->seqNum);
@@ -503,7 +503,7 @@ DefaultIEW<Impl>::squashDueToBranch(DynInstPtr &inst, ThreadID tid)
 
 template<class Impl>
 void
-DefaultIEW<Impl>::squashDueToMemOrder(DynInstPtr &inst, ThreadID tid)
+DefaultIEW<Impl>::squashDueToMemOrder(const DynInstPtr& inst, ThreadID tid)
 {
     DPRINTF(IEW, "[tid:%i]: Memory violation, squashing violator and younger "
             "insts, PC: %s [sn:%i].\n", tid, inst->pcState(), inst->seqNum);
@@ -566,28 +566,28 @@ DefaultIEW<Impl>::unblock(ThreadID tid)
 
 template<class Impl>
 void
-DefaultIEW<Impl>::wakeDependents(DynInstPtr &inst)
+DefaultIEW<Impl>::wakeDependents(const DynInstPtr& inst)
 {
     instQueue.wakeDependents(inst);
 }
 
 template<class Impl>
 void
-DefaultIEW<Impl>::rescheduleMemInst(DynInstPtr &inst)
+DefaultIEW<Impl>::rescheduleMemInst(const DynInstPtr& inst)
 {
     instQueue.rescheduleMemInst(inst);
 }
 
 template<class Impl>
 void
-DefaultIEW<Impl>::replayMemInst(DynInstPtr &inst)
+DefaultIEW<Impl>::replayMemInst(const DynInstPtr& inst)
 {
     instQueue.replayMemInst(inst);
 }
 
 template<class Impl>
 void
-DefaultIEW<Impl>::blockMemInst(DynInstPtr& inst)
+DefaultIEW<Impl>::blockMemInst(const DynInstPtr& inst)
 {
     instQueue.blockMemInst(inst);
 }
@@ -601,7 +601,7 @@ DefaultIEW<Impl>::cacheUnblocked()
 
 template<class Impl>
 void
-DefaultIEW<Impl>::instToCommit(DynInstPtr &inst)
+DefaultIEW<Impl>::instToCommit(const DynInstPtr& inst)
 {
     // This function should not be called after writebackInsts in a
     // single cycle.  That will cause problems with an instruction
@@ -1578,7 +1578,7 @@ DefaultIEW<Impl>::tick()
 
 template <class Impl>
 void
-DefaultIEW<Impl>::updateExeInstStats(DynInstPtr &inst)
+DefaultIEW<Impl>::updateExeInstStats(const DynInstPtr& inst)
 {
     ThreadID tid = inst->threadNumber;
 
@@ -1610,7 +1610,7 @@ DefaultIEW<Impl>::updateExeInstStats(DynInstPtr &inst)
 
 template <class Impl>
 void
-DefaultIEW<Impl>::checkMisprediction(DynInstPtr &inst)
+DefaultIEW<Impl>::checkMisprediction(const DynInstPtr& inst)
 {
     ThreadID tid = inst->threadNumber;
 
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