[PATCH] D27152: Merge strings using sharded hash tables.

[Rui Ueyama via llvm-commits]

On Sat, Dec 10, 2016 at 3:41 PM, Sean Silva <chisophugis at gmail.com> wrote:

>
>
> On Sat, Dec 10, 2016 at 2:51 PM, Rafael Avila de Espindola <
> rafael.espindola at gmail.com> wrote:
>
>> Rui Ueyama <ruiu at google.com> writes:
>> >
>> > This means we produce different results with threads disabled?
>> >
>> >
>> > Yes. But as long as you pass the same command line arguments, results
>> are
>> > the same.
>>
>> That is still undesirable. Using --no-threads is convenient for
>> debugging and it makes it harder if that produces a different result.
>>
>>
> This is basically a policy decision. Is `--threads`/`--no-threads` allowed
> to affect the output? Whatever we decide, we should document the decision
> because it has pretty profound consequences.
>

We could define a policy per a flag, but that's probably too complicated.
I'd propose the following simple policy.

"We guarantee LLD to produce the exact same result if the same input files
and the same command line arguments are given in the same order."

It's easy to remember and should suffice from the users' perspective.

(although I think that our build ID already ends up different for
> threads/no-threads?)
>

We always compute a tree hash, so the build-id is not affected by
threads/no-threads.

-- Sean Silva
>
>
>
>> Cheers,
>> Rafael
>>
>
>
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