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] Fix TNEW load forwarding with instable types. Date: Mon, 3 Jul 2023 19:24:01 +0000 [thread overview] Message-ID: <ZKMgUdZR9z82OItc@tarantool.org> (raw) In-Reply-To: <20230510213002.5153-1-skaplun@tarantool.org> Sergey, Thanks for the patch! LGTM, considering the fixes made for the comments left by Max. On 11.05.23, Sergey Kaplun via Tarantool-patches wrote: > From: Mike Pall <mike> > > (cherry picked from commit d4c0c6e17ef7edf1f2893bc807746b80612e63e9) > > During loop unrolling IR instructions are coped, substituted and > re-emitted for the FOLD/CSE/etc. pipeline. Assume, we have the following > loop-carried dependency: we create a new table or load some stored one > depends on iteration number. In case when we copy the emitted ALOAD IR Side note: Changed the part after the colon the following way | we create a new table or load the stored one depending on the | iteration number. > instruction (from from the stored table), we copy it as is, including > loading type. But the ALOAD from the new table created (on the previous > iteration) should have nil type, so the assertion in `fwd_ahload()` is > failed. > > This patch replaces the assertion to `return 0` to avoid the assertion > failure and stop forwarding in such situations. > > But the emitted type-guarded ALOAD will lead to the persistent failure > of the assertion guard on the trace. Hence, another one fix should be Side note: Removed this sentence, as we discussed. > added. Also, TDUP IR is affected, too. > See also the issue mentioned in the test. > > Sergey Kaplun: > * added the description and the test for the problem > > Part of tarantool/tarantool#8516 > --- > > Branch: https://github.com/tarantool/luajit/tree/skaplun/lj-994-instable-types-during-loop-unroll > PR: https://github.com/tarantool/tarantool/pull/8642 > Related issues: > * https://github.com/tarantool/tarantool/issues/8516 > * https://github.com/LuaJIT/LuaJIT/issues/994 > > I don't mention the 994 intentionally to avoid Mike bothering. Also, it > isn't the origin of this commit. Quite the opposite: as a result of this > backporting the following issue was created. > > I prefer to backport the patches (this one and the prospective for 994) > separately. So, after this patch is backported, it doesn't add any > critical bugs (always failing guard just creates a new side trace), but > helps to avoid conflicts for future backporting (sadly remembered > "Improve assertions."). > > src/lj_opt_mem.c | 3 +- > ...instable-types-during-loop-unroll.test.lua | 53 +++++++++++++++++++ > 2 files changed, 55 insertions(+), 1 deletion(-) > create mode 100644 test/tarantool-tests/lj-994-instable-types-during-loop-unroll.test.lua > <snipped> > -- > 2.34.1 > -- Best regards, IM
next prev parent reply other threads:[~2023-07-03 19:32 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-05-10 21:30 Sergey Kaplun via Tarantool-patches 2023-05-15 10:30 ` Maxim Kokryashkin via Tarantool-patches 2023-05-15 10:35 ` Maxim Kokryashkin via Tarantool-patches 2023-05-18 20:55 ` Sergey Kaplun via Tarantool-patches 2023-07-03 19:24 ` Igor Munkin via Tarantool-patches [this message] 2023-07-04 17:09 ` Igor Munkin via Tarantool-patches
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