From: Igor Munkin via Tarantool-patches <tarantool-patches@dev.tarantool.org> To: Sergey Kaplun <skaplun@tarantool.org> Cc: tarantool-patches@dev.tarantool.org Subject: Re: [Tarantool-patches] [PATCH luajit] Detect inconsistent renames even in the presence of sunk values. Date: Mon, 2 Aug 2021 16:34:25 +0300 [thread overview] Message-ID: <20210802133425.GB27855@tarantool.org> (raw) In-Reply-To: <YQbIgbDXTEI1vunu@root> Sergey, Thanks for your review! On 01.08.21, Sergey Kaplun wrote: > Hi, Igor! > Thanks for the patch! > > Is there no point to simplify the test -- we have 5 different traces, > when really need the only one (with RENAME between two possible jump > to fallback branches with restoration from snapshot)? Well... It was a tough issue to provide a stable reproducer to Mike. Reducing this one is a much more complex issue: we need to compile a trace for a loop with a rename emitted between two guards with the same exitno in a variant part and leave the compiled loop via the guard at the first iteration before the emitted RENAME. Sounds more complex than even the existing test, doesn't it? > Feel free to ignore. Ignoring. > > Side note: also, we should test that sunk optimization still works, > shouldn't we? Emm, nothing in the patch affects sink optimization per se, so if it's OK without the patch, it's still OK with it. > Feel free to ignore. Ignoring. > > Otherwise, LGTM. Added your tag: | Reviewed-by: Sergey Kaplun <skaplun@tarantool.org> > > On 24.07.21, Igor Munkin wrote: > > From: Mike Pall <mike> > > > > Reported by Igor Munkin. > > > > (cherry picked from commit 33e3f4badfde8cd9c202cedd1f4ed9275bc92e7d) > > > > Side exits with the same exitno use the same snapshot for restoring > > guest stack values. This obliges all guards related to the particular > > snapshot use the same RegSP mapping for the values to be restored at the > > trace exit. RENAME emitted prior to the guard for the same snapshot > > leads to the aforementioned invariant violation. > > This sentence a little bit unclear to me: > > 1) Leads how? RENAME changes the effective register to be used prior to the particular snapshot[1]. Hence if RENAME is emitted between the guards with the same exitno, RegSP mapping is inconsistent for the former one. > 2) Do you mean it in terms of recording (i. e. the reverse instrucions > recording order) or not? The trace is recorded in a direct order, but *assembled* in a reverse order. I implies the latter one. > > > The easy way to save > > > the snapshot consistency is spilling the renamed IR reference, that is > > done in scope of <asm_snap_checkrename>. > > > > However, the previous <asm_snap_checkrename> implementation considers > > only the IR references explicitly mentioned in the snapshot. E.g. if > > there is a sunk[1] object to be restored at the trace exit, and the > > renamed reference is a *STORE to that object, the spill slot is not > > allocated. As a result an invalid value is stored while unsinking that > > object at all corresponding side exits prior to the emitted renaming. > > > > To handle also those IR references implicitly used in the snapshot, all > > non-constant and non-sunk references are added to the Bloom filter (it's > > worth to mention that two hash functions are used to reduce collisions > > for the cases when the number of IR references emitted between two > > different snapshots exceeds the filter size). New <asm_snap_checkrename> > > implementation tests whether the renamed IR reference is in the filter > > and forces a spill slot for it as a result. > > > > [1]: http://wiki.luajit.org/Allocation-Sinking-Optimization > > > > Igor Munkin: > > * added the description and the test for the problem > > > > Resolves tarantool/tarantool#5118 > > Follows up tarantool/tarantool#4252 > > > > Signed-off-by: Igor Munkin <imun@tarantool.org> > > --- > > > > Related issues: > > * https://github.com/tarantool/tarantool/issues/5118 > > * https://github.com/tarantool/tarantool/issues/4252 > > * https://github.com/LuaJIT/LuaJIT/issues/584 > > Branch: https://github.com/tarantool/luajit/tree/imun/lj-584-bad-renames-for-sunk-values > > CI: https://github.com/tarantool/tarantool/commit/b35e2ee > > > > src/lj_asm.c | 25 ++++--- > > ...j-584-bad-renames-for-sunk-values.test.lua | 69 +++++++++++++++++++ > > 2 files changed, 81 insertions(+), 13 deletions(-) > > create mode 100644 test/tarantool-tests/lj-584-bad-renames-for-sunk-values.test.lua > > <snipped> > > -- > > 2.25.0 > > > > -- > Best regards, > Sergey Kaplun [1]: http://wiki.luajit.org/SSA-IR-2.0#miscellaneous-ops -- Best regards, IM
next prev parent reply other threads:[~2021-08-02 13:58 UTC|newest] Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-07-24 17:23 Igor Munkin via Tarantool-patches 2021-07-27 13:53 ` Sergey Ostanevich via Tarantool-patches 2021-08-03 20:28 ` Igor Munkin via Tarantool-patches 2021-08-04 12:49 ` Vitaliia Ioffe via Tarantool-patches 2021-08-01 16:14 ` Sergey Kaplun via Tarantool-patches 2021-08-02 13:34 ` Igor Munkin via Tarantool-patches [this message] 2021-08-04 15:07 ` Igor Munkin via Tarantool-patches
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20210802133425.GB27855@tarantool.org \ --to=tarantool-patches@dev.tarantool.org \ --cc=imun@tarantool.org \ --cc=skaplun@tarantool.org \ --subject='Re: [Tarantool-patches] [PATCH luajit] Detect inconsistent renames even in the presence of sunk values.' \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: link
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox