[PATCH] Ranger : Do not process abnormal ssa-names.
Aldy Hernandez
aldyh@redhat.com
Fri Oct 15 14:21:02 GMT 2021
On 10/15/21 3:50 PM, Andrew MacLeod wrote:
> I've been looking at the pathological time issue ranger has with the
> testcase from, uuuuuh.. PR 97623 I think. I've lost the details, but
> kept the file since it was showing unpleasant behaviour.
>
> Most of the time is spent in callbacks from substitute_and_fold to
> value_on_edge() dealing with PHI results and arguments. Turns out, its
> virtually all wasted time dealing with SSA_NAMES with the
> OCCURS_IN_ABNORMAL_PHI flag set..
>
> This patch tells ranger not to consider any SSA_NAMEs which occur in
> abnormal PHIs. This reduces the memory footprint of all the caches, and
> also has a ripple effect with the new threader code which uses the GORI
> exports and imports tables, making it faster as well as no ssa-name with
> the abnormal flag set will be entered into the tables.
>
> That alone was not quite enough, as all the sheer volume of call backs
> still took time, so I added checks in the value_of_* class of routines
> used by substitute_and_fold to indicate there is no constant value
> available for any SSA_NAME with that flag set.
>
> On my x86_64 box, before this change, that test case looked like:
>
> tree VRP : 7.76 ( 4%) 0.23 ( 5%) 8.02
> ( 4%) 537k ( 0%)
> tree VRP threader : 7.20 ( 4%) 0.08 ( 2%) 7.28 (
> 4%) 392k ( 0%)
> tree Early VRP : 39.22 ( 22%) 0.07 ( 2%) 39.44 (
> 22%) 1142k ( 0%)
>
> And with this patch , the results are:
>
> tree VRP : 7.57 ( 6%) 0.26 ( 5%) 7.85
> ( 6%) 537k ( 0%)
> tree VRP threader : 0.62 ( 0%) 0.02 ( 0%) 0.65
> ( 0%) 392k ( 0%)
> tree Early VRP : 4.00 ( 3%) 0.01 ( 0%) 4.03
> ( 3%) 1142k ( 0%)
>
> Which is a significant improvement, both for EVRP and the threader..
>
> The patch adjusts the ranger folder, as well as the hybrid folder.
>
> bootstrapped on x86_64-pc-linux-gnu with no regressions and no missed
> cases that I have been able to find.
>
> I don't want to push it quite yet as I wanted feedback to make sure we
> don't actually do anything I'm not aware of with SSA_NAMES which have
> the ABNORMAL_PHI flag set. Most of the code i can find in VRP and
> vr-values appears to punt, so I presume not even considering those names
> is fine?
The backward threader skips both edges with EDGE_ABNORMAL set as well as
phi results to have SSA_NAME_OCCURS_IN_ABNORMAL_PHI.
The forward threader skips out on all abnormal edges as well. It seems
to even avoid threading through blocks where one of the 2 outgoing edges
is abnormal. Dunno if this was an oversight, or just being extra careful.
Anywhoooo, at least from the threaders you're safe.
Aldy
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