[LLVMdev] Section specialization & COFF.

[r4start]

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.
>>>>
>>>> _______________________________________________
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>>>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
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>>>>
>>> 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.
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