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Re: [Qemu-devel] [RFC v1 3/3] target/arm: Correct exclusive store return
From: |
Alistair Francis |
Subject: |
Re: [Qemu-devel] [RFC v1 3/3] target/arm: Correct exclusive store return value |
Date: |
Fri, 11 Aug 2017 13:29:13 -0700 |
On Fri, Aug 11, 2017 at 1:24 PM, Richard Henderson
<address@hidden> wrote:
> On 08/11/2017 01:13 PM, Alistair Francis wrote:
>>>> + tcg_gen_ext_i64(val, val, memop);
>>>
>>> What is this addition intended to accomplish? Because of the position
>>> within
>>> the code, you know that memop contains MO_64, so that this is a no-op.
>>
>> This is when size == 2 so it's a 32bit operation so memop contains MO_32.
>
> It's a paired 32-bit operation, so we're operating on a 64-bit quantity. So
> extending from 32-bits would be actively wrong.
>From what I can see though, the 32bit memop is carried into the
tcg_gen_atomic_cmpxchg_i64() call so the value returned to tmp is
masked by the 32bit operation.
Is passing down MO_32 into tcg_gen_atomic_cmpxchg_i64() wrong then as
it ends up as a 64-bit operation?
My TCG knowledge is pretty limited here.
Thanks,
Alistair
>
>
> r~
>
- [Qemu-devel] [RFC v1 0/3] Fixup exclusive store logic, Alistair Francis, 2017/08/11
- [Qemu-devel] [RFC v1 1/3] target/arm: Update the memops for exclusive load, Alistair Francis, 2017/08/11
- [Qemu-devel] [RFC v1 3/3] target/arm: Correct exclusive store return value, Alistair Francis, 2017/08/11
- Re: [Qemu-devel] [RFC v1 3/3] target/arm: Correct exclusive store return value, Richard Henderson, 2017/08/11
- Re: [Qemu-devel] [RFC v1 3/3] target/arm: Correct exclusive store return value, Alistair Francis, 2017/08/11
- Re: [Qemu-devel] [RFC v1 3/3] target/arm: Correct exclusive store return value, Richard Henderson, 2017/08/11
- Re: [Qemu-devel] [RFC v1 3/3] target/arm: Correct exclusive store return value,
Alistair Francis <=
- Re: [Qemu-devel] [RFC v1 3/3] target/arm: Correct exclusive store return value, Richard Henderson, 2017/08/11
- Re: [Qemu-devel] [RFC v1 3/3] target/arm: Correct exclusive store return value, Alistair Francis, 2017/08/11
- Re: [Qemu-devel] [RFC v1 3/3] target/arm: Correct exclusive store return value, Alistair Francis, 2017/08/11
[Qemu-devel] [RFC v1 2/3] tcg/tcg-op: Expose the tcg_gen_ext_i* functions, Alistair Francis, 2017/08/11