From: Jeff Law <jeffreyalaw@gmail.com>
To: gcc-patches@gcc.gnu.org
Subject: Re: [PATCH v2 00/10] [RISC-V] Atomics improvements [PR100265/PR100266]
Date: Tue, 11 Oct 2022 17:14:05 -0600 [thread overview]
Message-ID: <a28ca2f0-7f86-2c2c-49f2-f6579fbd0e2e@gmail.com> (raw)
In-Reply-To: <mhng-40d97af4-272d-435f-a211-7661c87c22fe@palmer-ri-x1c9>
On 10/11/22 13:31, Palmer Dabbelt wrote:
> On Tue, 11 Oct 2022 12:06:27 PDT (-0700), Vineet Gupta wrote:
>> Hi Christoph, Kito,
>>
>> On 5/5/21 12:36, Christoph Muellner via Gcc-patches wrote:
>>> This series provides a cleanup of the current atomics implementation
>>> of RISC-V:
>>>
>>> * PR100265: Use proper fences for atomic load/store
>>> * PR100266: Provide programmatic implementation of CAS
>>>
>>> As both are very related, I merged the patches into one series.
>>>
>>> The first patch could be squashed into the following patches,
>>> but I found it easier to understand the chances with it in place.
>>>
>>> The series has been tested as follows:
>>> * Building and testing a multilib RV32/64 toolchain
>>> (bootstrapped with riscv-gnu-toolchain repo)
>>> * Manual review of generated sequences for GCC's atomic builtins API
>>>
>>> The programmatic re-implementation of CAS benefits from a REE
>>> improvement
>>> (see PR100264):
>>> https://gcc.gnu.org/pipermail/gcc-patches/2021-April/568680.html
>>> If this patch is not in place, then an additional extension instruction
>>> is emitted after the SC.W (in case of RV64 and CAS for uint32_t).
>>>
>>> Further, the new CAS code requires cbranch INSN helpers to be present:
>>> https://gcc.gnu.org/pipermail/gcc-patches/2021-May/569689.html
>>
>> I was wondering is this patchset is blocked on some technical grounds.
>
> There's a v3 (though I can't find all of it, so not quite sure what
> happened), but IIUC that still has the same fundamental problems that
> all these have had: changing over to the new fence model may by an ABI
> break and the split CAS implementation doesn't ensure eventual success
> (see Jim's comments). Not sure if there's other comments floating
> around, though, that's just what I remember.
Do we have a pointer to the ABI discussion. I've been meaning to
familiarize myself with the issues in this space and that seems like a
good place to start given its blocking progress on the atomics.
jeff
prev parent reply other threads:[~2022-10-11 23:14 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-05 19:36 Christoph Muellner
2021-05-05 19:36 ` [PATCH v2 01/10] RISC-V: Simplify memory model code [PR 100265] Christoph Muellner
2021-05-05 19:36 ` [PATCH v2 02/10] RISC-V: Emit proper memory ordering suffixes for AMOs " Christoph Muellner
2021-05-05 19:36 ` [PATCH v2 03/10] RISC-V: Eliminate %F specifier from riscv_print_operand() " Christoph Muellner
2021-05-05 19:36 ` [PATCH v2 04/10] RISC-V: Use STORE instead of AMOSWAP for atomic stores " Christoph Muellner
2021-05-05 19:36 ` [PATCH v2 05/10] RISC-V: Emit fences according to chosen memory model " Christoph Muellner
2021-05-05 19:36 ` [PATCH v2 06/10] RISC-V: Implement atomic_{load,store} " Christoph Muellner
2021-05-05 19:36 ` [PATCH v2 07/10] RISC-V: Model INSNs for LR and SC [PR 100266] Christoph Muellner
2021-05-05 19:36 ` [PATCH v2 08/10] RISC-V: Add s.ext-consuming " Christoph Muellner
2021-05-05 19:36 ` [PATCH v2 09/10] RISC-V: Provide programmatic implementation of CAS " Christoph Muellner
2021-05-06 0:27 ` Jim Wilson
2021-05-05 19:36 ` [PATCH v2 10/10] RISC-V: Introduce predicate "riscv_sync_memory_operand" " Christoph Muellner
2022-10-11 19:06 ` [PATCH v2 00/10] [RISC-V] Atomics improvements [PR100265/PR100266] Vineet Gupta
2022-10-11 19:31 ` Palmer Dabbelt
2022-10-11 20:46 ` Christoph Müllner
2022-10-11 23:31 ` Vineet Gupta
2022-10-12 0:15 ` Palmer Dabbelt
2022-10-12 8:03 ` Christoph Müllner
2022-10-13 23:11 ` Jeff Law
2022-10-12 17:16 ` Andrea Parri
2022-10-20 19:01 ` Andrea Parri
2022-10-29 5:02 ` Jeff Law
2022-10-13 23:04 ` Jeff Law
2022-10-13 22:39 ` Jeff Law
2022-10-13 23:14 ` Palmer Dabbelt
2022-10-14 11:03 ` Christoph Müllner
2022-10-14 20:39 ` Jeff Law
2022-10-14 21:57 ` Palmer Dabbelt
2022-10-15 0:31 ` Palmer Dabbelt
2022-10-14 0:14 ` Vineet Gupta
2022-10-11 23:14 ` Jeff Law [this message]
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