[LLVMdev] Section specialization & COFF.

[Michael Spencer]

On Wed, Oct 31, 2012 at 9:41 AM, r4start <r4start at gmail.com> wrote:
> On 24/10/12 17:03, r4start wrote:
>>
>> On 23/10/12 01:30, Michael Spencer wrote:
>>>
>>> On Mon, Oct 22, 2012 at 7:53 AM, r4start <r4start at gmail.com> wrote:
>>>>
>>>> On 20/10/12 03:15, Michael Spencer wrote:
>>>>>
>>>>> On Fri, Oct 19, 2012 at 2:55 AM, r4start <r4start at gmail.com> wrote:
>>>>>>
>>>>>> Hi all.
>>>>>>
>>>>>> While compiling next code
>>>>>> @A = weak unnamed_addr constant { i32, i32, i32 } { i32 0, i32 0, i32
>>>>>> 0
>>>>>> },
>>>>>> section ".data"
>>>>>> was discovered that llc ignores weak linkage if we emit it in COFF
>>>>>> object.
>>>>>> Attached patch solves this problem, please review.
>>>>>>
>>>>>> I found some similar tests in test/Objects/Inputs. Should I do
>>>>>> something
>>>>>> like trivial.ll checking or there is a better way
>>>>>> to check patch behaviour?
>>>>>>
>>>>>>    - Dmitry Sokolov.
>>>>>>
>>>>>> _______________________________________________
>>>>>> LLVM Developers mailing list
>>>>>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>>>>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>>>>>>
>>>>> test/Object is not the right place for the test. It should probably go
>>>>> in test/MC/COFF as a .ll file, although technically it's codegen...
>>>>>
>>>>> Also, I'm pretty sure this is wrong for MinGW. What do msvc and
>>>>> mingw-gcc produce for c code that generates this?
>>>>>
>>>>> - Michael Spencer
>>>>
>>>> For this c code(see attachments) cl, mingw and clang produce different
>>>> coff's(was used dumpbin with option /ALL):
>>>> 1) Cl generate separate COMDAT section with linkage selection "pick any"
>>>> 2) Mingw place this value to regular section and place special auxilary
>>>> record to symbol table
>>>> 3) Clang without patch just ignore weakness of this value and place it
>>>> to
>>>> regular section.
>>>>     But for weak values without explicit section specification it use
>>>> cl-like
>>>> way. i.e. generate
>>>>     separate COMDAT section with a little difference in naming (unique
>>>> suffix
>>>> after $)
>>>> 4) With this patch clang will generate correct COMDAT section for values
>>>> with explicit section specification.
>>>>
>>>> The problem is in backend. When we have explicit section specification
>>>> linkage type is ignored.
>>>
>>> Looks fine with a test in CodeGen.
>>>
>>> - Michael Spencer
>>
>> Was added test.
>> Please review.
>> Patch was made by Dmitry Puzirev.
>
> Ping?

lgtm.

- Michael Spencer