[llvm-dev] Can I build llvm with only a handful of source files compiled for debug?

[Praveen Velliengiri via llvm-dev]

I used Split Dwarf, but actually in some builds only, I don't know why I
stopped using it. Thanks I will use them, and tell you how far it reduces
the total time.

Yeah, understood that but I use llvm as shared libraries, which  already
costs me observable overhead while debugging. For what it's worth, I will
try my hands on it by compressing debug-info.

On Thu, 15 Aug 2019 at 00:58, David Blaikie <dblaikie at gmail.com> wrote:

>
>
> On Wed, Aug 14, 2019 at 12:22 PM Praveen Velliengiri <
> praveenvelliengiri at gmail.com> wrote:
>
>> Regarding resource constraint problems, I didn't build llvm on much
>> heavier machine previously, so it is difficult for me to tell whether my
>> build is taking longer than expected trivially, fresh build (+ clang, lldb)
>> takes time. But rebuild are actually fast.
>>
>
> Are you already using split DWARF (& gdb-index)?
>
>
>> I will use -compress-debug-sections with the full build and rebuilds and
>> see how fast it is :)
>> Making an assumption here: since debug-info is compressed, i think it may
>> cause a overhead for the debugger. Is it true? If so, it overhead is
>> observable to some extent ?
>>
>
> Compression will add some CPU compile time (& some link time, technically
> - since the linker will decompress the sections to link them), but might
> save time when writing fewer bytes to disk (& save disk usage). Similarly
> decompression by the debugger might slow things, but reading fewer bytes
> from disk may speed them up - will depend on the CPU versus disk IO speeds.
>
>
>>
>> On Thu, 15 Aug 2019 at 00:33, David Blaikie <dblaikie at gmail.com> wrote:
>>
>>> Are you already using split DWARF & still having resource constraint
>>> problems? (oh, you could also compress debug info,
>>> -Wa,-compress-debug-sections)
>>>
>>>
>>>
>>> On Wed, Aug 14, 2019 at 12:00 PM Praveen Velliengiri <
>>> praveenvelliengiri at gmail.com> wrote:
>>>
>>>> Actually, I have same question, If llvm build provides a option similar
>>>> to that, it will be lot more easier for people doing development in
>>>> relatively less (compute, storage) PC's.
>>>>
>>>>
>>>> On Thu, 15 Aug 2019 at 00:22, David Blaikie via llvm-dev <
>>>> llvm-dev at lists.llvm.org> wrote:
>>>>
>>>>> Nothing supported, though might not be too hard to do by hand.
>>>>>
>>>>> If you're having long link times, lots of disk usage, and slow gdb
>>>>> startup time I'd recommend enabling split DWARF (LLVM_USE_SPLIT_DWARF=ON,
>>>>> and CMAKE_EXE_LINKER_FLAGS_*=-Wl,-gdb-index in cmake) if you haven't
>>>>> already.
>>>>>
>>>>> On Wed, Aug 14, 2019 at 11:40 AM Robert Henry via llvm-dev <
>>>>> llvm-dev at lists.llvm.org> wrote:
>>>>>
>>>>>> In order to minimize edit/compile/debug turn time, is there a way to
>>>>>> compile llvm tools so that the majority of the files are compiled as if for
>>>>>> release (eg, no debug symbols), and only the handful of files that I have
>>>>>> touched are compiled for debugging? This will reduce the load on the file
>>>>>> system, linker and gdb tremendously.  At present, AFAICT, it's all or
>>>>>> nothing.
>>>>>> _______________________________________________
>>>>>> LLVM Developers mailing list
>>>>>> llvm-dev at lists.llvm.org
>>>>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>>>
>>>>> _______________________________________________
>>>>> LLVM Developers mailing list
>>>>> llvm-dev at lists.llvm.org
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>>>>>
>>>>
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