[llvm-dev] Using std::chrono

[Pavel Labath via llvm-dev]

Hello all,

I'd like to add a std::chrono support header to libSupport
<https://reviews.llvm.org/D25416>. My main motivation is remove LLDB's
TimeValue class in favor of std::chrono, but I think we could do the
same for llvm::sys::TimeValue as well - the class was added a very
long time ago, when std::chrono did not exist yet, but now it should
be supported by all compilers. I've tried rewriting some of the uses
in llvm, and despite the apparent verboseness of std::chrono, it makes
the code shorter most of the time, and (due to the separation between
time points and durations) also safer - I think I also found some bugs
where we were adding two time points, but I'll need to verify that.

What do you think?
pl


On 6 October 2016 at 23:52, Zachary Turner via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> VS2013 support is dropped in about 1 week from now :)
>
> On Thu, Oct 6, 2016 at 11:37 PM Mueller-Roemer, Johannes Sebastian
> <Johannes.Sebastian.Mueller-Roemer at igd.fraunhofer.de> wrote:
>>
>> Visual Studio up to and including VS2013 implements
>> std::chrono::high_resolution_clock in an absolutely unusable manner (it is a
>> very low resolution clock…) [1]. Also, division is implemented incorrectly
>> [2]. I have run into both issues in my private developments, so I would
>> avoid them as long as VS2013 is supported by LLVM (I believe it still is?).
>>
>>
>>
>>     [1]: https://stackoverflow.com/questions/31643279
>>
>>     [2]: https://stackoverflow.com/questions/26372596
>>
>>
>>
>>
>>
>> From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of
>> Zachary Turner via llvm-dev
>> Sent: Friday, October 7, 2016 03:11
>> To: llvm-dev <llvm-dev at lists.llvm.org>
>> Subject: [llvm-dev] Using std::chrono
>>
>>
>>
>> Hi all,
>>
>> We're considering using std::chrono more heavily in lldb. However, A quick
>> search of the llvm, clang, and lld codebases shos almost zero usage of
>> chrono. I wanted to see if this was for technical reasons (eg some compiler
>> doesn't support it well) or simply because nobody has needed it yet. If it's
>> the former then I'd like to be aware of the issues so we don't fall into any
>> traps.
>>
>> If it's the latter, then we're good to go. Would it be worth adding any
>> chrono helper functions to llvm/Support? On the one hand, it seems generally
>> useful. But on the other hand, if nobody's using it yet, maybe it's not
>> generally useful enough.
>>
>> Also, are there any chrono experts around who would be willing to review
>> some patches?
>
>
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