From 0c50a0b4fe3956f9d2e08e75d47c9cbd79bf0268 Mon Sep 17 00:00:00 2001 From: Rekai Gonzalez-Alberquilla 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 Reviewed-on: https://gem5-review.googlesource.com/c/13105 Reviewed-by: Andreas Sandberg Reviewed-by: Jason Lowe-Power Maintainer: Andreas Sandberg Maintainer: Jason Lowe-Power --- src/cpu/o3/decode_impl.hh | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) (limited to 'src/cpu/o3/decode_impl.hh') diff --git a/src/cpu/o3/decode_impl.hh b/src/cpu/o3/decode_impl.hh index 15ec76f5a..51c1b9de1 100644 --- a/src/cpu/o3/decode_impl.hh +++ b/src/cpu/o3/decode_impl.hh @@ -288,7 +288,7 @@ DefaultDecode::unblock(ThreadID tid) template void -DefaultDecode::squash(DynInstPtr &inst, ThreadID tid) +DefaultDecode::squash(const DynInstPtr &inst, ThreadID tid) { DPRINTF(Decode, "[tid:%i]: [sn:%i] Squashing due to incorrect branch " "prediction detected at decode.\n", tid, inst->seqNum); @@ -650,8 +650,6 @@ DefaultDecode::decodeInsts(ThreadID tid) ++decodeRunCycles; } - DynInstPtr inst; - std::queue &insts_to_decode = decodeStatus[tid] == Unblocking ? skidBuffer[tid] : insts[tid]; @@ -661,7 +659,7 @@ DefaultDecode::decodeInsts(ThreadID tid) while (insts_available > 0 && toRenameIndex < decodeWidth) { assert(!insts_to_decode.empty()); - inst = insts_to_decode.front(); + DynInstPtr inst = std::move(insts_to_decode.front()); insts_to_decode.pop(); -- cgit v1.2.3