[llvm-commits] [llvm] r78872 - /llvm/trunk/lib/Target/X86/AsmPrinter/X86ATTAsmPrinter.cpp

[Nick Kledzik]

On Aug 22, 2009, at 4:45 PM, Chris Lattner wrote:

> Hi Dale, sorry for follow up on this so late.
>
> On Aug 13, 2009, at 11:26 AM, Dale Johannesen wrote:
> On Aug 12, 2009, at 8:53 PMPDT, Chris Lattner wrote:
>>> On Aug 12, 2009, at 5:28 PM, Dale Johannesen wrote:
>>>
>>>> Author: johannes
>>>> Date: Wed Aug 12 19:28:52 2009
>>>> New Revision: 78872
>>>>
>>>> URL: http://llvm.org/viewvc/llvm-project?rev=78872&view=rev
>>>> Log:
>>>> Symbols with LinkerPrivateLinkage are weak.
>>>> This allows WebKit to build again.
>>>
>>> What specifically does this change?
>>
>> It changes
>>
>>      .private_extern l_objc_msgSend_fixup_alloc
>>       .section        __DATA,__objc_msgrefs,coalesced
>> 	.align  4
>> l_objc_msgSend_fixup_alloc:
>>       .quad   _objc_msgSend_fixup
>>       .quad   L_OBJC_METH_VAR_NAME_16
>>
>> to
>>
>>      .private_extern l_objc_msgSend_fixup_alloc
>>       .section        __DATA,__objc_msgrefs,coalesced
>>       .globl l_objc_msgSend_fixup_alloc
>>       .weak_definition l_objc_msgSend_fixup_alloc
>> 	.align  4
>> l_objc_msgSend_fixup_alloc:
>>       .quad   _objc_msgSend_fixup
>>       .quad   L_OBJC_METH_VAR_NAME_16
>>
>> If you want to know what the ObjC metadata is doing, I don't know,  
>> but this is what gcc does.
>>
>>> Can you add a regtest?
>>
>> I suppose.  There are some in the gcc testsuite.  I was asked not  
>> to run it anymore but somebody should be; it's the best tests we  
>> have for ObjC metadata.
>>
>>> Do ppc/arm need a similar fix?
>>
>> Probably, good catch, I'll look at it.
>>
>
> I still don't understand what this is doing.  "l" labels are not  
> visible outside of their translation unit.  Why could they possibly  
> need to be marked as weak definitions?  They can't be overridden by  
> other translation units, so it doesn't make sense (to me) for them  
> to have to be weak.

Chris, it is 'L' labels that are visible on in their translation  
unit.  'l' labels are visible throughout the linkage unit.   Making  
these weak-hidden enables the linker to coalesce duplicates.

-Nick