On 10/31/18 12:34 AM, bin.cheng wrote:
> Hi,
> This patch fixes AutoFDO breakage on trunk. The main reason for breakage is
> AutoFDO
> relies on standalone edge count computing and propagating profile
> count/probability info
> on CFG, but in new infra, edge count is actually computed from probability,
> which leads
> to chicken-egg problem and corrupted profile count. This patch fixes the
> issue by using
> explicit edge count.
>
> There is another issue not touched yet that, in quite common case, profiled
> samples are
> not enough and profile info computed for lots of blocks is ZERO. In the
> future, we may
> add some heuristics checking quality of sampled counts and reverting to
> guessed profile
> count if necessary. I think change made in this patch is also needed for
> that.
>
> Package mysql server is used in test of this patch set. It can't be compiled
> with autofdo
> on trunk, even with compilation issues worked-around, there isn't performance
> improvement.
> I local experiments, with this patch set it's improved by 12.3%, 4.3%
> irrespectively for
> read-only/write-heavy benchmarks. Unfortunately, this patch set was written
> against
> GCC 8 branch a while ago, improvement gets worse on trunk and I haven't
> investigated
> the reason yet. I guess there are still other issues which need to be fixed
> in the future.
>
> Bootstrap and test on x86_64 in patch set. Is it OK?
>
> Thanks,
> bin
> 2018-10-31 Bin Cheng <bin.ch...@linux.alibaba.com>
>
> * auto-profile.c (AFDO_EINFO): New macro.
> (struct edge_info): New structure.
> (is_edge_annotated, set_edge_annotated): Delete.
> (afdo_propagate_edge, afdo_propagate_circuit, afdo_propagate): Remove
> parameter. Adjust edge count computation and annotation using struct
> edge_info.
> (afdo_calculate_branch_prob): Ditto.
> (afdo_annotate_cfg): Simplify code setting basic block profile count.
>
>
> 0004-Fix-AutoFDO-breakage-after-profile-count-rewriting.patch
>
> From 6506c12d1b633b6d1bfae839b3633a4f99b3a481 Mon Sep 17 00:00:00 2001
> From: chengbin <bin.ch...@linux.alibaba.com>
> Date: Mon, 20 Aug 2018 15:25:02 +0800
> Subject: [PATCH 4/4] Fix AutoFDO breakage after profile count rewriting.
>
> ---
> gcc/auto-profile.c | 190
> ++++++++++++++++++++++++++---------------------------
> 1 file changed, 95 insertions(+), 95 deletions(-)
>
> diff --git a/gcc/auto-profile.c b/gcc/auto-profile.c
> index cde4f41c1d9..ff3ea23d830 100644
> --- a/gcc/auto-profile.c
> +++ b/gcc/auto-profile.c
> @@ -101,6 +101,17 @@ along with GCC; see the file COPYING3. If not see
> namespace autofdo
> {
>
> +/* Intermediate edge info used when propagating AutoFDO profile information.
> + We can't edge->count() directly since it's computed from edge's
> probability
> + while probability is yet not decided during propagation. */
> +#define AFDO_EINFO(e) ((struct edge_info *) e->aux)
> +struct edge_info
> +{
> + edge_info () : count (profile_count::zero ().afdo ()), annotated_p (false)
> {}
> + profile_count count;
> + bool annotated_p;
> +};
edge_info isn't POD, so make it a class rather than a struct.
OK with that change assuming it does not have a hard dependency on prior
patches in this series.
jeff
