[OE-core] [meta-clang] LLVM shared library support

[Khem Raj]

On Thu, Mar 9, 2017 at 1:32 PM, Martin Kelly <mkelly at xevo.com> wrote:
> On 03/09/2017 01:06 PM, Khem Raj wrote:
>>
>> On Fri, Mar 3, 2017 at 12:09 PM, Khem Raj <raj.khem at gmail.com> wrote:
>>>
>>>
>>> meta-clang has only provided static compiler thus far, so using shared
>>> or static did not matter as much in fact it could be helping with
>>> faster compile
>>> times that we see with clang. However, there is no binding to keep it
>>> static
>>> link. Feel free to send a pull request to change it.
>>
>>
>> I did try this and I see a considerable slowdown in compiler speed. I
>> changed
>> two things at a time so may be its the other
>>
>> diff --git a/recipes-devtools/clang/clang_git.bb
>> b/recipes-devtools/clang/clang_git.bb
>> index 6c6e66a..7de2be1 100644
>> --- a/recipes-devtools/clang/clang_git.bb
>> +++ b/recipes-devtools/clang/clang_git.bb
>> @@ -73,7 +73,8 @@ EXTRA_OECMAKE_append_class-nativesdk = "\
>>                 -DCLANG_TABLEGEN=${STAGING_BINDIR_NATIVE}/clang-tblgen \
>>  "
>>  EXTRA_OECMAKE_append_class-target = "\
>> -               -DLLVM_ENABLE_PIC=False \
>> +               -DBUILD_SHARED_LIBS=ON \
>> +               -DLLVM_ENABLE_PIC=ON \
>>                 -DLLVM_TABLEGEN=${STAGING_BINDIR_NATIVE}/llvm-tblgen \
>>                 -DCLANG_TABLEGEN=${STAGING_BINDIR_NATIVE}/clang-tblgen \
>>                 -DLLVM_TARGETS_TO_BUILD=${@get_clang_target_arch(bb, d)} \
>>
>>>
>
> Those are the exact changes I have been testing with; -DLLVM_ENABLE_PIC=ON
> is certainly necessary to prevent QA errors regarding text relocation, so
> you can't really make the changes in isolation. That said, the change is
> still very useful, as there are some programs that use only shared
> libLLVM.so, and without them you can't really use them with bitbake.
>

slow down is 6x when using clang to compile on target, I dont know if such
a patch would be a good thing from compiler pov.

> I hope to have a pull request for you soon once I iron out the rest of the
> issues.