r203052 - Construct GlobalValues with the correct linkage instead of using setLinkage.

[Steven Wu]

Hi Rafael

Sorry for a separate (and late) email since I don’t have the email back to March. And sorry for sending it again since I used the wrong email address for the previous and gets rejected by cfe-commit.
I found a problem compiling ObjC recently and I can only trace to the change in this patch.
This patch is indeed a functional change when coming to protocols that are forward declared and implemented in other files (which now generates a warning but not back then).
Originally, the codegen uses a deal with this case by initialize all dependent protocols to ExternalLinkage and change the linkage back when these protocols get processed.
For the external and forward-declared protocols will not get processed and remained ExternalLinkage.
Here is a testcase:

 @interface NSObject @end
 
 @protocol p1;
 
 @protocol p2 <p1>
 
 - (void)s1;
 
 @end
 
 @interface I1 : NSObject <p2>
 
 - (void)s2;
 @end
 
 @implementation I1
 
 - (void)s1 {
       NSLog(@"s1");
 }
 - (void)s2 {
       NSLog(@"s2");
 }
 @end
 
I am not familiar with ObjC standard so I am not sure if this is 100% legal but this patch causes the compiler fatal error.
Steven


> Author: rafael
> Date: Wed Mar  5 19:10:46 2014
> New Revision: 203052
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=203052&view=rev <http://llvm.org/viewvc/llvm-project?rev=203052&view=rev>
> Log:
> Construct GlobalValues with the correct linkage instead of using setLinkage.
> 
> Modified:
>     cfe/trunk/lib/CodeGen/CGObjCMac.cpp
> 
> Modified: cfe/trunk/lib/CodeGen/CGObjCMac.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGObjCMac.cpp?rev=203052&r1=203051&r2=203052&view=diff <http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGObjCMac.cpp?rev=203052&r1=203051&r2=203052&view=diff>
> ==============================================================================
> --- cfe/trunk/lib/CodeGen/CGObjCMac.cpp (original)
> +++ cfe/trunk/lib/CodeGen/CGObjCMac.cpp Wed Mar  5 19:10:46 2014
> @@ -2660,8 +2660,8 @@ llvm::Constant *CGObjCMac::GetOrEmitProt
>                                                     Values);
>  
>    if (Entry) {
> -    // Already created, fix the linkage and update the initializer.
> -    Entry->setLinkage(llvm::GlobalValue::PrivateLinkage);
> +    // Already created, update the initializer.
> +    assert(Entry->getLinkage() == llvm::GlobalValue::PrivateLinkage);
>      Entry->setInitializer(Init);
>    } else {
>      Entry =
> @@ -6242,10 +6242,9 @@ llvm::Constant *CGObjCNonFragileABIMac::
>      // reference or not. At module finalization we add the empty
>      // contents for protocols which were referenced but never defined.
>      Entry =
> -      new llvm::GlobalVariable(CGM.getModule(), ObjCTypes.ProtocolnfABITy, false,
> -                               llvm::GlobalValue::ExternalLinkage,
> -                               0,
> -                               "\01l_OBJC_PROTOCOL_$_" + PD->getName());
> +        new llvm::GlobalVariable(CGM.getModule(), ObjCTypes.ProtocolnfABITy,
> +                                 false, llvm::GlobalValue::WeakAnyLinkage, 0,
> +                                 "\01l_OBJC_PROTOCOL_$_" + PD->getName());
>      Entry->setSection("__DATA,__datacoal_nt,coalesced");
>    }
>  
> @@ -6358,8 +6357,8 @@ llvm::Constant *CGObjCNonFragileABIMac::
>                                                     Values);
>  
>    if (Entry) {
> -    // Already created, fix the linkage and update the initializer.
> -    Entry->setLinkage(llvm::GlobalValue::WeakAnyLinkage);
> +    // Already created, update the initializer.
> +    assert(Entry->getLinkage() == llvm::GlobalValue::WeakAnyLinkage);
>      Entry->setInitializer(Init);
>    } else {
>      Entry =


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