[lldb-dev] 64bit atomic ops on 32bit platforms

[Pavel Labath via lldb-dev]

On 9 August 2017 at 20:18, Joerg Sonnenberger via lldb-dev
<lldb-dev at lists.llvm.org> wrote:
> On Wed, Aug 02, 2017 at 03:47:56PM +0200, Joerg Sonnenberger via lldb-dev wrote:
>> (a) Make the mutex explicit if 64bit operations are not lock-free.
>>
>> or
>>
>> (b) Weaken the consistency constraints to provide eventually-consistent
>> times by splitting the field into explicit 32bit chunks. This makes the
>> write side get predictable timings at the expensive of the summaries
>> being potentially off a bit in the case of races.
>
> Ping? Given that this is a pretty annoying regression, I would like to
> address this for 5.0, but that means knowing how much effort I need to
> invest in different LLVM projects...

A bit late to the party, but I think (b) sounds fine. I take it the
timings will be off only when the operation overflows the lower 32 bit
value, and the summary is printed before the higher 32 bits are
updated

An option (c) I can offer is to switch to microsecond timers on 32-bit
platforms, and accept the fact that the timers will wrap around after
an hour or so.

pl