llvm dev - Aug 2019 - Can I build llvm with only a handful of source files compiled for debug?

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.
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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
>
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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
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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Clang has a way to achieve this. Once you've built LLVM without debug info,
you can then delete the objects or modify the sources you want to debug and then
rebuild with something like 'CCC_OVERRIDE_OPTIONS="+-g +-O0"
ninja'. The newly built files will have debug info.
> On Aug 14, 2019, at 11:40, 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 <mailto:llvm-dev at lists.llvm.org>
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
<https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev>
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On Wed, Aug 14, 2019 at 06:40:17PM +0000, Robert Henry via llvm-dev
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.
Disclaimer I have only tested this while working on Clang, but I assume
it works for the entire LLVM project.

I have enabled shared libraries in CMake. Then I add the following lines
to the CMakeLists.txt, for example clang/lib/Parse/CMakeLists.txt

set_source_files_properties(
  ParseDeclCXX.cpp
  ParseDecl.cpp
  Parser.cpp
  ParseStmt.cpp
  ParseExpr.cpp
  ParseExprCXX.cpp
  ParseInit.cpp

  PROPERTIES
  COMPILE_FLAGS "-O0 -g"
)

Then rebuild the clangParse target and have the debug symbols available.
Hope this helps.


Kind regards,
Mark de Wever

Since we are talking about a long link time and no one has mentioned about
lld so far, I'd like to make sure that you are using lld, which is
significantly faster than most other linkers.

On Thu, Aug 15, 2019 at 3:40 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
>
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