From: Hans Boehm <hboehm@google.com>
To: Palmer Dabbelt <palmer@rivosinc.com>
Cc: jeffreyalaw@gmail.com, "Patrick O'Neill" <patrick@rivosinc.com>,
gcc-patches@gcc.gnu.org, gnu-toolchain@rivosinc.com,
Vineet Gupta <vineetg@rivosinc.com>,
Andrew Waterman <andrew@sifive.com>,
kito.cheng@sifive.com, Daniel Lustig <dlustig@nvidia.com>,
cmuellner@gcc.gnu.org, Andrea Parri <andrea@rivosinc.com>
Subject: Re: [PATCH v5 06/11] RISC-V: Strengthen atomic stores
Date: Fri, 28 Apr 2023 14:42:50 -0700 [thread overview]
Message-ID: <CAMOCf+iF_JFx8+Gi1EKrQ6H2e64sNfm+YWYGYp6HQjBdmDMbGg@mail.gmail.com> (raw)
In-Reply-To: <mhng-ad6f4065-2273-475e-9495-f652f0b03573@palmer-ri-x1c9>
[-- Attachment #1: Type: text/plain, Size: 1884 bytes --]
The concern with making the new behavior non-default is of course that the
generated code will eventually end up on an A.7-capable platform.
An A.6-classic option for compiling code that will never run on a newer
machine seems OK. But I'm not sure that seq_cst stores are dynamically
frequent enough in C++ code for this to be worth the trouble. Unlike loads,
they are also costly on x86, programmers may also have been somewhat
trained to avoid them where possible. (And probably where not possible, too
:-( )
Hans
On Fri, Apr 28, 2023 at 10:43 AM Palmer Dabbelt <palmer@rivosinc.com> wrote:
> On Fri, 28 Apr 2023 10:40:15 PDT (-0700), jeffreyalaw@gmail.com wrote:
> >
> >
> > On 4/27/23 10:22, Patrick O'Neill wrote:
> >> This change makes atomic stores strictly stronger than table A.6 of the
> >> ISA manual. This mapping makes the overall patchset compatible with
> >> table A.7 as well.
> >>
> >> 2023-04-27 Patrick O'Neill <patrick@rivosinc.com>
> >>
> >> PR 89835
> > Should be "PR target/89835"
> >
> >>
> >> gcc/ChangeLog:
> >>
> >> * config/riscv/sync.md:
> > Needs some text here :-)
> >
> >
> > I'm not objecting to this patch, but I think we've got an option
> > question about whether or not this approach is too expensive for
> > existing or soon arriving implementations.
> >
> > If the decision on that topic is to just pay the cost, then this patch
> > is fine. If we decide to make compatibility optional to avoid the
> > additional cost, then this will need suitable adjustments.
>
> IMO the only hardware that's going to be here by gcc-14 and to have
> enough concurrency for these to matter is the Ventana stuff. I think
> you're the only one who can figure out if these are slow, at least until
> that stuff is availiable outside the lab.
>
> So are they too slow for you?
>
> >
> > Jeff
>
next prev parent reply other threads:[~2023-04-28 21:43 UTC|newest]
Thread overview: 98+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20220407182918.294892-1-patrick@rivosinc.com>
2023-04-05 21:01 ` [PATCH v2 0/8] RISCV: Implement ISA Manual Table A.6 Mappings Patrick O'Neill
2023-04-05 21:01 ` [PATCH v2 1/8] RISCV: Eliminate SYNC memory models Patrick O'Neill
2023-04-05 21:01 ` [PATCH v2 2/8] RISCV: Enforce Libatomic LR/SC SEQ_CST Patrick O'Neill
2023-04-05 21:01 ` [PATCH v2 3/8] RISCV: Enforce atomic compare_exchange SEQ_CST Patrick O'Neill
2023-04-05 21:01 ` [PATCH v2 4/8] RISCV: Add AMO release bits Patrick O'Neill
2023-04-05 21:01 ` [PATCH v2 5/8] RISCV: Eliminate AMO op fences Patrick O'Neill
2023-04-05 21:01 ` [PATCH v2 6/8] RISCV: Weaken compare_exchange LR/SC pairs Patrick O'Neill
2023-04-05 21:01 ` [PATCH v2 7/8] RISCV: Weaken atomic stores Patrick O'Neill
2023-04-05 21:01 ` [PATCH v2 8/8] RISCV: Weaken mem_thread_fence Patrick O'Neill
2023-04-10 18:23 ` [PATCH v3 00/10] RISCV: Implement ISA Manual Table A.6 Mappings Patrick O'Neill
2023-04-10 18:23 ` [PATCH v3 01/10] RISCV: Eliminate SYNC memory models Patrick O'Neill
2023-04-10 18:23 ` [PATCH v3 02/10] RISCV: Enforce Libatomic LR/SC SEQ_CST Patrick O'Neill
2023-04-10 18:23 ` [PATCH v3 03/10] RISCV: Enforce atomic compare_exchange SEQ_CST Patrick O'Neill
2023-04-10 18:23 ` [PATCH v3 04/10] RISCV: Add AMO release bits Patrick O'Neill
2023-04-10 18:23 ` [PATCH v3 05/10] RISCV: Strengthen atomic stores Patrick O'Neill
2023-04-10 18:23 ` [PATCH v3 06/10] RISCV: Eliminate AMO op fences Patrick O'Neill
2023-04-10 18:23 ` [PATCH v3 07/10] RISCV: Weaken compare_exchange LR/SC pairs Patrick O'Neill
2023-04-10 18:23 ` [PATCH v3 08/10] RISCV: Weaken mem_thread_fence Patrick O'Neill
2023-04-10 18:23 ` [PATCH v3 09/10] RISCV: Weaken atomic loads Patrick O'Neill
2023-04-10 18:23 ` [PATCH v3 10/10] RISCV: Table A.6 conformance tests Patrick O'Neill
2023-04-14 17:09 ` [PATCH v4 00/10] RISCV: Implement ISA Manual Table A.6 Mappings Patrick O'Neill
2023-04-14 17:09 ` [PATCH v4 01/10] RISCV: Eliminate SYNC memory models Patrick O'Neill
2023-04-14 17:09 ` [PATCH v4 02/10] RISCV: Enforce Libatomic LR/SC SEQ_CST Patrick O'Neill
2023-04-14 17:09 ` [PATCH v4 03/10] RISCV: Enforce atomic compare_exchange SEQ_CST Patrick O'Neill
2023-04-14 17:09 ` [PATCH v4 04/10] RISCV: Add AMO release bits Patrick O'Neill
2023-04-14 17:09 ` [PATCH v4 05/10] RISCV: Strengthen atomic stores Patrick O'Neill
2023-04-14 17:09 ` [PATCH v4 06/10] RISCV: Eliminate AMO op fences Patrick O'Neill
2023-04-14 17:09 ` [PATCH v4 07/10] RISCV: Weaken compare_exchange LR/SC pairs Patrick O'Neill
2023-04-14 17:09 ` [PATCH v4 08/10] RISCV: Weaken mem_thread_fence Patrick O'Neill
2023-04-14 17:09 ` [PATCH v4 09/10] RISCV: Weaken atomic loads Patrick O'Neill
2023-04-14 17:09 ` [PATCH v4 10/10] RISCV: Table A.6 conformance tests Patrick O'Neill
2023-04-27 16:22 ` [PATCH v5 00/11] RISC-V: Implement ISA Manual Table A.6 Mappings Patrick O'Neill
2023-04-27 16:22 ` [PATCH v5 01/11] RISC-V: Eliminate SYNC memory models Patrick O'Neill
2023-04-28 16:23 ` Jeff Law
2023-05-02 20:12 ` [Committed " Patrick O'Neill
2023-04-27 16:22 ` [PATCH v5 02/11] RISC-V: Enforce Libatomic LR/SC SEQ_CST Patrick O'Neill
2023-04-28 16:50 ` Jeff Law
2023-05-02 20:12 ` [Committed " Patrick O'Neill
2023-04-27 16:22 ` [PATCH v5 03/11] RISC-V: Enforce subword atomic " Patrick O'Neill
2023-05-02 20:14 ` [Committed " Patrick O'Neill
2023-04-27 16:22 ` [PATCH v5 04/11] RISC-V: Enforce atomic compare_exchange SEQ_CST Patrick O'Neill
2023-04-28 17:23 ` Jeff Law
2023-05-02 20:15 ` [Committed " Patrick O'Neill
2023-04-27 16:22 ` [PATCH v5 05/11] RISC-V: Add AMO release bits Patrick O'Neill
2023-04-28 17:34 ` Jeff Law
2023-05-02 20:16 ` Patrick O'Neill
2023-04-27 16:22 ` [PATCH v5 06/11] RISC-V: Strengthen atomic stores Patrick O'Neill
2023-04-28 17:40 ` Jeff Law
2023-04-28 17:43 ` Palmer Dabbelt
2023-04-28 21:42 ` Hans Boehm [this message]
2023-04-28 22:21 ` Hans Boehm
2023-04-30 17:10 ` Jeff Law
2023-05-02 20:18 ` [Committed " Patrick O'Neill
2023-05-02 16:11 ` [PATCH v5 " Patrick O'Neill
2023-04-27 16:22 ` [PATCH v5 07/11] RISC-V: Eliminate AMO op fences Patrick O'Neill
2023-04-28 17:43 ` Jeff Law
2023-05-02 20:19 ` [Committed " Patrick O'Neill
2023-04-27 16:22 ` [PATCH v5 08/11] RISC-V: Weaken LR/SC pairs Patrick O'Neill
2023-04-28 17:56 ` Jeff Law
2023-05-02 20:19 ` [Committed " Patrick O'Neill
2023-04-27 16:22 ` [PATCH v5 09/11] RISC-V: Weaken mem_thread_fence Patrick O'Neill
2023-04-28 18:00 ` Jeff Law
2023-05-02 20:20 ` [Committed " Patrick O'Neill
2023-05-03 12:18 ` [PATCH v5 " Andreas Schwab
2023-05-03 12:22 ` Martin Liška
2023-04-27 16:23 ` [PATCH v5 10/11] RISC-V: Weaken atomic loads Patrick O'Neill
2023-04-28 18:04 ` Jeff Law
2023-05-02 20:20 ` [Committed " Patrick O'Neill
2023-04-27 16:23 ` [PATCH v5 11/11] RISC-V: Table A.6 conformance tests Patrick O'Neill
2023-04-28 18:07 ` Jeff Law
2023-05-02 20:28 ` [Committed " Patrick O'Neill
2023-04-27 17:20 ` [PATCH v5 00/11] RISC-V: Implement ISA Manual Table A.6 Mappings Andrea Parri
2023-04-28 16:14 ` Jeff Law
2023-04-28 16:29 ` Palmer Dabbelt
2023-04-28 17:44 ` Patrick O'Neill
2023-04-28 18:18 ` Patrick O'Neill
[not found] ` <CAMOCf+hK9nedV+UeENbTn=Uy3RpYLeMt04mLiLmDsZyNm83CCg@mail.gmail.com>
2023-04-30 16:37 ` Jeff Law
2023-07-25 18:01 ` [gcc13 backport 00/12] " Patrick O'Neill
2023-07-25 18:01 ` [gcc13 backport 01/12] RISC-V: Eliminate SYNC memory models Patrick O'Neill
2023-07-25 18:01 ` [gcc13 backport 02/12] RISC-V: Enforce Libatomic LR/SC SEQ_CST Patrick O'Neill
2023-07-25 18:01 ` [gcc13 backport 03/12] RISC-V: Enforce subword atomic " Patrick O'Neill
2023-07-25 18:01 ` [gcc13 backport 04/12] RISC-V: Enforce atomic compare_exchange SEQ_CST Patrick O'Neill
2023-07-25 18:01 ` [gcc13 backport 05/12] RISC-V: Add AMO release bits Patrick O'Neill
2023-07-25 18:02 ` [gcc13 backport 06/12] RISC-V: Strengthen atomic stores Patrick O'Neill
2023-07-25 18:02 ` [gcc13 backport 07/12] RISC-V: Eliminate AMO op fences Patrick O'Neill
2023-07-25 18:02 ` [gcc13 backport 08/12] RISC-V: Weaken LR/SC pairs Patrick O'Neill
2023-07-25 18:02 ` [gcc13 backport 09/12] RISC-V: Weaken mem_thread_fence Patrick O'Neill
2023-07-25 18:02 ` [gcc13 backport 10/12] RISC-V: Weaken atomic loads Patrick O'Neill
2023-07-25 18:02 ` [gcc13 backport 11/12] RISC-V: Table A.6 conformance tests Patrick O'Neill
2023-07-25 18:02 ` [gcc13 backport 12/12] riscv: fix error: control reaches end of non-void function Patrick O'Neill
2023-07-26 1:22 ` Kito Cheng
2023-07-26 17:41 ` Patrick O'Neill
2023-07-25 19:50 ` [gcc13 backport 00/12] RISC-V: Implement ISA Manual Table A.6 Mappings Jakub Jelinek
2023-07-25 20:01 ` Palmer Dabbelt
2023-07-25 21:02 ` Jeff Law
2023-07-25 21:16 ` Palmer Dabbelt
2023-07-25 19:58 ` Palmer Dabbelt
2023-07-31 16:19 ` [Committed] " Patrick O'Neill
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