[lldb-dev] [Release-testers] [7.0.0 Release] rc1 has been tagged

[Hans Wennborg via lldb-dev]

On Wed, Aug 22, 2018 at 3:48 AM, Dimitry Andric <dimitry at andric.com> wrote:
> On 22 Aug 2018, at 05:58, Wei Mi <wmi at google.com> wrote:
>>
>> On Fri, Aug 17, 2018 at 1:27 PM, Dimitry Andric <dimitry at andric.com> wrote:
>> On 16 Aug 2018, at 00:51, Joerg Sonnenberger via llvm-dev <llvm-dev at lists.llvm.org> wrote:
>> > On Tue, Aug 07, 2018 at 09:49:16PM +0200, Dimitry Andric via llvm-dev wrote:
>> >> This is a regression caused by https://reviews.llvm.org/rL323281:
>> >>
>> >> ------------------------------------------------------------------------
>> >> r323281 | wmi | 2018-01-23 23:27:57 +0000 (Tue, 23 Jan 2018) | 12 lines
>> >>
>> >> Adjust MaxAtomicInlineWidth for i386/i486 targets.
>> >>
>> >> This is to fix the bug reported in https://bugs.llvm.org/show_bug.cgi?id=34347#c6.
>> >> Currently, all  MaxAtomicInlineWidth of x86-32 targets are set to 64. However,
>> >> i386 doesn't support any cmpxchg related instructions. i486 only supports cmpxchg.
>> >> So in this patch MaxAtomicInlineWidth is reset as follows:
>> >> For i386, the MaxAtomicInlineWidth should be 0 because no cmpxchg is supported.
>> >> For i486, the MaxAtomicInlineWidth should be 32 because it supports cmpxchg.
>> >> For others 32 bits x86 cpu, the MaxAtomicInlineWidth should be 64 because of cmpxchg8b.
>> >
>> > This seems to be somewhat undesirable. Does *anyone* care about real
>> > i386 support at this point? NetBSD certainly doesn't and I think we are
>> > already the odd man for a number of cases like this.
>>
>>
>> Yes, and since this causes quite a number of regressions for us, I would
>> really prefer this revision to be reverted, at least in the 7.0.0
>> branch.  I have already reverted it locally in our FreeBSD project
>> branch for importing llvm/clang 7.0.0.  Hans, what is your opinion about
>> this?
>>
>> -Dimitry
>>
>>
>> Sorry I missed the thread for quite a while. Dimitry, I am very confused because you reported the issue in https://bugs.llvm.org/show_bug.cgi?id=34347#c6, so you want r323281 to be reverted and let llvm to generate cmxchg8b instruction for i486?
>
> Since it's been doing this for a number of years now, I don't think it would be bad at all, at least not for FreeBSD.  At least, a lot more effort is needed to supply properly working atomic libcalls for 64 bit values on i386.  (They can't be implemented without at least a bit of kernel assistance.)

According to the release schedule we should tag RC2 today. Do you
think there's any chance of getting this figured out by today?

Thanks,
Hans