Implement the "linker_private_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. However, this linkage isn't specific to
Objective-C.

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".

Currently only supported on Darwin platforms.

llvm-svn: 107433
diff --git a/llvm/test/CodeGen/ARM/2009-08-23-linkerprivate.ll b/llvm/test/CodeGen/ARM/2009-08-23-linkerprivate.ll
index 0fad533..392c70a 100644
--- a/llvm/test/CodeGen/ARM/2009-08-23-linkerprivate.ll
+++ b/llvm/test/CodeGen/ARM/2009-08-23-linkerprivate.ll
@@ -2,7 +2,7 @@
 
 ; ModuleID = '/Volumes/MacOS9/tests/WebKit/JavaScriptCore/profiler/ProfilerServer.mm'
 
-@"\01l_objc_msgSend_fixup_alloc" = linker_private hidden global i32 0, section "__DATA, __objc_msgrefs, coalesced", align 16		; <i32*> [#uses=0]
+@"\01l_objc_msgSend_fixup_alloc" = linker_private_weak hidden global i32 0, section "__DATA, __objc_msgrefs, coalesced", align 16
 
 ; CHECK: .globl l_objc_msgSend_fixup_alloc
 ; CHECK: .weak_definition l_objc_msgSend_fixup_alloc
diff --git a/llvm/test/CodeGen/PowerPC/2009-08-23-linkerprivate.ll b/llvm/test/CodeGen/PowerPC/2009-08-23-linkerprivate.ll
index 12c4c99..0bde2d5 100644
--- a/llvm/test/CodeGen/PowerPC/2009-08-23-linkerprivate.ll
+++ b/llvm/test/CodeGen/PowerPC/2009-08-23-linkerprivate.ll
@@ -2,7 +2,7 @@
 
 ; ModuleID = '/Volumes/MacOS9/tests/WebKit/JavaScriptCore/profiler/ProfilerServer.mm'
 
-@"\01l_objc_msgSend_fixup_alloc" = linker_private hidden global i32 0, section "__DATA, __objc_msgrefs, coalesced", align 16		; <i32*> [#uses=0]
+@"\01l_objc_msgSend_fixup_alloc" = linker_private_weak hidden global i32 0, section "__DATA, __objc_msgrefs, coalesced", align 16
 
 ; CHECK: .globl l_objc_msgSend_fixup_alloc
 ; CHECK: .weak_definition l_objc_msgSend_fixup_alloc
diff --git a/llvm/test/CodeGen/X86/2009-08-23-linkerprivate.ll b/llvm/test/CodeGen/X86/2009-08-23-linkerprivate.ll
index 3da8f00..90fac15 100644
--- a/llvm/test/CodeGen/X86/2009-08-23-linkerprivate.ll
+++ b/llvm/test/CodeGen/X86/2009-08-23-linkerprivate.ll
@@ -2,7 +2,7 @@
 
 ; ModuleID = '/Volumes/MacOS9/tests/WebKit/JavaScriptCore/profiler/ProfilerServer.mm'
 
-@"\01l_objc_msgSend_fixup_alloc" = linker_private hidden global i32 0, section "__DATA, __objc_msgrefs, coalesced", align 16		; <i32*> [#uses=0]
+@"\01l_objc_msgSend_fixup_alloc" = linker_private_weak hidden global i32 0, section "__DATA, __objc_msgrefs, coalesced", align 16
 
 ; CHECK: .globl l_objc_msgSend_fixup_alloc
 ; CHECK: .weak_definition l_objc_msgSend_fixup_alloc
diff --git a/llvm/test/Feature/linker_private_linkages.ll b/llvm/test/Feature/linker_private_linkages.ll
new file mode 100644
index 0000000..19bcbb4
--- /dev/null
+++ b/llvm/test/Feature/linker_private_linkages.ll
@@ -0,0 +1,6 @@
+; RUN: llvm-as < %s | llvm-dis > %t1.ll
+; RUN: llvm-as %t1.ll -o - | llvm-dis > %t2.ll
+; RUN: diff %t1.ll %t2.ll
+
+@foo = linker_private hidden global i32 0
+@bar = linker_private_weak hidden global i32 0