Introducing the "linker_weak" linkage type. This will be used for Objective-C
metadata types which should be marked as "weak", but which the linker will
remove upon final linkage. For example, the "objc_msgSend_fixup_alloc" symbol is
defined like this:

       .globl l_objc_msgSend_fixup_alloc
       .weak_definition l_objc_msgSend_fixup_alloc
       .section __DATA, __objc_msgrefs, coalesced
       .align 3
l_objc_msgSend_fixup_alloc:
        .quad   _objc_msgSend_fixup
        .quad   L_OBJC_METH_VAR_NAME_1

This is different from the "linker_private" linkage type, because it can't have
the metadata defined with ".weak_definition".


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@107205 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/Mangler.cpp b/lib/Target/Mangler.cpp
index 4ef017a..fc2f78d 100644
--- a/lib/Target/Mangler.cpp
+++ b/lib/Target/Mangler.cpp
@@ -118,6 +118,9 @@
     } else if (PrefixTy == Mangler::LinkerPrivate) {
       const char *Prefix = MAI.getLinkerPrivateGlobalPrefix();
       OutName.append(Prefix, Prefix+strlen(Prefix));
+    } else if (PrefixTy == Mangler::LinkerWeak) {
+      const char *Prefix = MAI.getLinkerWeakGlobalPrefix();
+      OutName.append(Prefix, Prefix+strlen(Prefix));
     }
 
     const char *Prefix = MAI.getGlobalPrefix();
@@ -182,6 +185,8 @@
     PrefixTy = Mangler::Private;
   else if (GV->hasLinkerPrivateLinkage())
     PrefixTy = Mangler::LinkerPrivate;
+  else if (GV->hasLinkerWeakLinkage())
+    PrefixTy = Mangler::LinkerWeak;
   
   // If this global has a name, handle it simply.
   if (GV->hasName()) {