Ping.
Thanks,
Kyrill
> On 13 Dec 2024, at 16:47, Kyrylo Tkachov <ktkac...@nvidia.com> wrote:
>
> Ping.
> Thanks,
> Kyrill
>
>> On 28 Nov 2024, at 11:22, Kyrylo Tkachov <ktkac...@nvidia.com> wrote:
>>
>> Ping.
>>
>>> On 15 Nov 2024, at 17:04, Kyrylo Tkachov <ktkac...@nvidia.com> wrote:
>>>
>>> Hi all,
>>>
>>> This is a patch submission following-up from the RFC at:
>>> https://gcc.gnu.org/pipermail/gcc/2024-November/245076.html
>>> The patch is rebased and retested against current trunk, some debugging code
>>> removed, comments improved and some fixes added as I've we've done more
>>> testing.
>>>
>>> ------------------------>8-----------------------------------------------------
>>> Implement partitioning and cloning in the callgraph to help locality.
>>> A new -flto-partition=locality flag is used to enable this.
>>> The majority of the logic is in the new IPA pass in ipa-locality-cloning.cc
>>> The optimization has two components:
>>> * Partitioning the callgraph so as to group callers and callees that
>>> frequently
>>> call each other in the same partition
>>> * Cloning functions that straddle multiple callchains and allowing each
>>> clone
>>> to be local to the partition of its callchain.
>>>
>>> The majority of the logic is in the new IPA pass in ipa-locality-cloning.cc.
>>> It creates a partitioning plan and does the prerequisite cloning.
>>> The partitioning is then implemented during the existing LTO partitioning
>>> pass.
>>>
>>> To guide these locality heuristics we use PGO data.
>>> In the absence of PGO data we use a static heuristic that uses the
>>> accumulated
>>> estimated edge frequencies of the callees for each function to guide the
>>> reordering.
>>> We are investigating some more elaborate static heuristics, in particular
>>> using
>>> the demangled C++ names to group template instantiatios together.
>>> This is promising but we are working out some kinks in the implementation
>>> currently and want to send that out as a follow-up once we're more confident
>>> in it.
>>>
>>> A new bootstrap-lto-locality bootstrap config is added that allows us to
>>> test
>>> this on GCC itself with either static or PGO heuristics.
>>> GCC bootstraps with both (normal LTO bootstrap and profiledbootstrap).
>>>
>>> With this optimization we are seeing good performance gains on some large
>>> internal workloads that stress the parts of the processor that is sensitive
>>> to code locality, but we'd appreciate wider performance evaluation.
>>>
>>> Bootstrapped and tested on aarch64-none-linux-gnu.
>>> Ok for mainline?
>>> Thanks,
>>> Kyrill
>>>
>>> Signed-off-by: Prachi Godbole <pgodb...@nvidia.com>
>>> Co-authored-by: Kyrylo Tkachov <ktkac...@nvidia.com>
>>>
>>> config/ChangeLog:
>>> * bootstrap-lto-locality.mk: New file.
>>>
>>> gcc/ChangeLog:
>>> * Makefile.in (OBJS): Add ipa-locality-cloning.o
>>> (GTFILES): Add ipa-locality-cloning.cc dependency.
>>> * common.opt (lto_partition_model): Add locality value.
>>> * flag-types.h (lto_partition_model): Add LTO_PARTITION_LOCALITY
>>> value.
>>> (enum lto_locality_cloning_model): Define.
>>> * lto-cgraph.cc (lto_set_symtab_encoder_in_partition): Add dumping
>>> of node
>>> and index.
>>> * params.opt (lto_locality_cloning_model): New enum.
>>> (lto-partition-locality-cloning): New param.
>>> (lto-partition-locality-frequency-cutoff): Likewise.
>>> (lto-partition-locality-size-cutoff): Likewise.
>>> (lto-max-locality-partition): Likewise.
>>> * passes.def: Add pass_ipa_locality_cloning.
>>> * timevar.def (TV_IPA_LC): New timevar.
>>> * tree-pass.h (make_pass_ipa_locality_cloning): Declare.
>>> * ipa-locality-cloning.cc: New file.
>>> * ipa-locality-cloning.h: New file.
>>>
>>> gcc/lto/ChangeLog:
>>> * lto-partition.cc: Include ipa-locality-cloning.h
>>> (add_node_references_to_partition): Define.
>>> (create_partition): Likewise.
>>> (lto_locality_map): Likewise.
>>> (lto_promote_cross_file_statics): Add extra dumping.
>>> * lto-partition.h (lto_locality_map): Declare.
>>> * lto.cc (do_whole_program_analysis): Handle
>>> LTO_PARTITION_LOCALITY.
>>>
>>> <0001-Introduce-flto-partition-locality.patch>
>>
>
