From: Patrick O'Neill <patrick@rivosinc.com>
To: Palmer Dabbelt <palmer@rivosinc.com>, jeffreyalaw@gmail.com
Cc: 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>,
hboehm@google.com
Subject: Re: [PATCH v5 00/11] RISC-V: Implement ISA Manual Table A.6 Mappings
Date: Fri, 28 Apr 2023 11:18:17 -0700 [thread overview]
Message-ID: <8c768ac5-5a12-4119-b43b-7652aec358a9@rivosinc.com> (raw)
In-Reply-To: <20873714-5809-0be2-35f0-91b76b80d7e5@rivosinc.com>
On 4/28/23 10:44, Patrick O'Neill wrote:
> On 4/28/23 09:29, Palmer Dabbelt wrote:
>> On Fri, 28 Apr 2023 09:14:00 PDT (-0700), jeffreyalaw@gmail.com wrote:
>>> On 4/27/23 10:22, Patrick O'Neill wrote:
...
>>>> LLVM mapping notes
>>>> --------
>>>> LLVM emits corresponding fences for atomic_signal_fence instructions.
>>>> This seems to be an oversight since AFAIK atomic_signal_fence acts
>>>> as a
>>>> compiler directive. GCC does not emit any fences for
>>>> atomic_signal_fence
>>>> instructions.
>>> This starts to touch on a larger concern. Specifically I'd really like
>>> the two compilers to be compatible in terms of the code they generate
>>> for the various atomics.
>>>
>>> What I worry about is code being written (by design or accident)
>>> that is
>>> dependent on the particular behavior of one compiler and then if that
>>> code gets built with the other compiler, and we end up different
>>> behavior. Worse yet, if/when this happens, it's likely to be tough to
>>> expose, reproduce & debug.
> Agreed.
>
> I'll open an issue with LLVM and see what they have to say about this
> particular behavior. Ideally we'd have perfectly compatible compilers
> (for atomic ops) by the end of this :)
>
> AFAICT GCC hasn't ever been emitting fences for these instructions.
> (& This behavior isn't touched by the patchset).
I re-ran the set of tests I was using and couldn't replicate LLVM's
behavior that was noted here. I think I mixed had up atomic_thread_fence
with atomic_signal_fence at some point.
That was the only difference I could find during my testing of this
patchset (other than the strengthened SEQ_CST store), so I think
GCC/LLVM atomics will be fully compatible once this patchset is applied.
next prev parent reply other threads:[~2023-04-28 18:18 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: " 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
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 [this message]
[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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