[llvm-dev] question about xray tls data initialization

[Dean Michael Berris via llvm-dev]

> On 23 Nov 2017, at 23:34, comic fans <comicfans44 at gmail.com> wrote:
> 
> On Wed, Nov 22, 2017 at 10:37 AM, Dean Michael Berris
> <dean.berris at gmail.com> wrote:
>> 
>> On 22 Nov 2017, at 02:32, comic fans <comicfans44 at gmail.com> wrote:
>> 
>> with some dirty hack , I've made xray runtime  'built' on windows ,
>> 
>> 
>> \o/
> 
> with more test, I've found that trampoline didn't got built for windows :/
> currently cmake didn't generate build rule for asm so its silently
> ignored(with msvc ide, but not ninja).
> we must have enable_language(ASM_MASM) to use masm, and trampoline
> also need ports.
> 

Right -- this is similar to issues we've run into trying to make XRay work / get built for Darwin too.

>> 
>> If you're alright with it, maybe you can send some patches to review,
>> preferably through the LLVM Phabricator instance? You can have me or Reid
>> (who knows more about COFF and the Windows stuff) as reviewers.
>> 
>> in AsmPrinter, copy/paster xray for coff target
>> 
>> InstMap = OutContext.getCOFFSection("xray_instr_map", 0,
>> SectionKind::getReadOnlyWithRel());
>> FnSledIndex = OutContext.getCOFFSection("xray_fn_idx",
>> 0,SectionKind::getReadOnlyWithRel());
>> 
>> in XRayArgs , allow windows platform to use xray args. with this,
>> generated code seems have sled and xray parts.
>> 
>> 
>> Nice, I suspect we can make this change with tests as well, which we can
>> build on incrementally.
> 
> where can I find some examples to test this xray part in llvm ?
> 

Those are in the llvm/test/CodeGen/X86/... -- in particular, searching for 'xray_' in the files there will be the best way of finding examples of what we're looking for to verify.

> 
>> in xray runtime,
>> bool atomic_compare_exchange_strong(volatile atomic_sint32_t *a,
>>                                          s32 *cmp,
>>                                          s32 xchg,
>>                                          memory_order mo)
>> is missed for MSVC , I take atomic_uint32_t implementation
>> 
>> 
>> This is in compiler-rt/lib/sanitizer_common/... right?
> 
> yes, sanitizer_atomic_msvc.h didn't provide this override. according
> to msdn of interlockedcompareexchange,  implementation for
> atomic_uint32_t should also works for atomic_sint32_t. this is a
> copy/paste but I think its short enough. any better suggestion ?
> 

I'm sure adding an implementation for atomic_sint32_t will be nice to have across platforms. :)

>> 
>> FunctionRecord pack , __attribute__((packed)) =>  #pragma
>> pack(push,1),  msvc also requires bitfields to be same type to pack
>> them together( all types => uint32_t)
>> 
>> 
>> Are you able to test this on other platforms?
> 
> I've tested this on linux64 (with clang) and it pass check-xray , but
> I don't have mac to test. if changing all attribute to pragma is
> desirable , I can submit a patch for that .


We're still working on getting XRay to build right and work on macOS so that shouldn't be a barrier. :)

A patch would be good there too.

Thanks again!

-- Dean

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