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.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@107433 91177308-0d34-0410-b5e6-96231b3b80d8

bindings/ada/llvm/llvm.ads

@@ -316,7 +316,8 @@ package llvm is
       LLVMExternalWeakLinkage,
       LLVMGhostLinkage,
       LLVMCommonLinkage,
-      LLVMLinkerPrivateLinkage);
+      LLVMLinkerPrivateLinkage,
+      LLVMLinkerPrivateWeakLinkage);
 
    for LLVMLinkage use
      (LLVMExternalLinkage            => 0,
@@ -333,7 +334,8 @@ package llvm is
       LLVMExternalWeakLinkage        => 11,
       LLVMGhostLinkage               => 12,
       LLVMCommonLinkage              => 13,
-      LLVMLinkerPrivateLinkage       => 14);
+      LLVMLinkerPrivateLinkage       => 14,
+      LLVMLinkerPrivateWeakLinkage   => 15);
 
    pragma Convention (C, LLVMLinkage);
 

docs/LangRef.html

@@ -24,6 +24,7 @@
         <ol>
           <li><a href="#linkage_private">'<tt>private</tt>' Linkage</a></li>
           <li><a href="#linkage_linker_private">'<tt>linker_private</tt>' Linkage</a></li>
+          <li><a href="#linkage_linker_private_weak">'<tt>linker_private_weak</tt>' Linkage</a></li>
           <li><a href="#linkage_internal">'<tt>internal</tt>' Linkage</a></li>
           <li><a href="#linkage_available_externally">'<tt>available_externally</tt>' Linkage</a></li>
           <li><a href="#linkage_linkonce">'<tt>linkonce</tt>' Linkage</a></li>
@@ -546,20 +547,24 @@ define i32 @main() {                                        <i>; i32()* </i>
 
 <dl>
   <dt><tt><b><a name="linkage_private">private</a></b></tt></dt>
-  <dd>Global values with private linkage are only directly accessible by objects
-      in the current module.  In particular, linking code into a module with an
-      private global value may cause the private to be renamed as necessary to
-      avoid collisions.  Because the symbol is private to the module, all
-      references can be updated. This doesn't show up in any symbol table in the
-      object file.</dd>
+  <dd>Global values with "<tt>private</tt>" linkage are only directly accessible
+      by objects in the current module. In particular, linking code into a
+      module with an private global value may cause the private to be renamed as
+      necessary to avoid collisions.  Because the symbol is private to the
+      module, all references can be updated. This doesn't show up in any symbol
+      table in the object file.</dd>
 
   <dt><tt><b><a name="linkage_linker_private">linker_private</a></b></tt></dt>
-  <dd>Similar to private, but the symbol is passed through the assembler and
-      removed by the linker after evaluation.  Note that (unlike private
-      symbols) linker_private symbols are subject to coalescing by the linker:
-      weak symbols get merged and redefinitions are rejected.  However, unlike
-      normal strong symbols, they are removed by the linker from the final
-      linked image (executable or dynamic library).</dd>
+  <dd>Similar to <tt>private</tt>, but the symbol is passed through the
+      assembler and evaluated by the linker. Unlike normal strong symbols, they
+      are removed by the linker from the final linked image (executable or
+      dynamic library).</dd>
+
+  <dt><tt><b><a name="linkage_linker_private_weak">linker_private_weak</a></b></tt></dt>
+  <dd>Similar to "<tt>linker_private</tt>", but the symbol is weak. Note that
+      <tt>linker_private_weak</tt> symbols are subject to coalescing by the
+      linker. The symbols are removed by the linker from the final linked image
+      (executable or dynamic library).</dd>
 
   <dt><tt><b><a name="linkage_internal">internal</a></b></tt></dt>
   <dd>Similar to private, but the value shows as a local symbol
@@ -623,8 +628,8 @@ define i32 @main() {                                        <i>; i32()* </i>
   <dt><tt><b><a name="linkage_weak_odr">weak_odr</a></b></tt></dt>
   <dd>Some languages allow differing globals to be merged, such as two functions
       with different semantics.  Other languages, such as <tt>C++</tt>, ensure
-      that only equivalent globals are ever merged (the "one definition rule" -
-      "ODR").  Such languages can use the <tt>linkonce_odr</tt>
+      that only equivalent globals are ever merged (the "one definition rule"
+      &mdash; "ODR").  Such languages can use the <tt>linkonce_odr</tt>
       and <tt>weak_odr</tt> linkage types to indicate that the global will only
       be merged with equivalent globals.  These linkage types are otherwise the
       same as their non-<tt>odr</tt> versions.</dd>

include/llvm-c/Core.h

@@ -226,7 +226,8 @@ typedef enum {
   LLVMExternalWeakLinkage,/**< ExternalWeak linkage description */
   LLVMGhostLinkage,       /**< Obsolete */
   LLVMCommonLinkage,      /**< Tentative definitions */
-  LLVMLinkerPrivateLinkage /**< Like Private, but linker removes. */
+  LLVMLinkerPrivateLinkage, /**< Like Private, but linker removes. */
+  LLVMLinkerPrivateWeakLinkage /**< Like LinkerPrivate, but is weak. */
 } LLVMLinkage;
 
 typedef enum {

include/llvm/GlobalValue.h

@@ -40,6 +40,7 @@ public:
     InternalLinkage,    ///< Rename collisions when linking (static functions).
     PrivateLinkage,     ///< Like Internal, but omit from symbol table.
     LinkerPrivateLinkage, ///< Like Private, but linker removes.
+    LinkerPrivateWeakLinkage, ///< Like LinkerPrivate, but weak.
     DLLImportLinkage,   ///< Function to be imported from DLL
     DLLExportLinkage,   ///< Function to be accessible from DLL.
     ExternalWeakLinkage,///< ExternalWeak linkage description.
@@ -132,11 +133,14 @@ public:
     return Linkage == PrivateLinkage;
   }
   static bool isLinkerPrivateLinkage(LinkageTypes Linkage) {
-    return Linkage==LinkerPrivateLinkage;
+    return Linkage == LinkerPrivateLinkage;
+  }
+  static bool isLinkerPrivateWeakLinkage(LinkageTypes Linkage) {
+    return Linkage == LinkerPrivateWeakLinkage;
   }
   static bool isLocalLinkage(LinkageTypes Linkage) {
     return isInternalLinkage(Linkage) || isPrivateLinkage(Linkage) ||
-      isLinkerPrivateLinkage(Linkage);
+      isLinkerPrivateLinkage(Linkage) || isLinkerPrivateWeakLinkage(Linkage);
   }
   static bool isDLLImportLinkage(LinkageTypes Linkage) {
     return Linkage == DLLImportLinkage;
@@ -158,7 +162,8 @@ public:
     return (Linkage == WeakAnyLinkage ||
             Linkage == LinkOnceAnyLinkage ||
             Linkage == CommonLinkage ||
-            Linkage == ExternalWeakLinkage);
+            Linkage == ExternalWeakLinkage ||
+            Linkage == LinkerPrivateWeakLinkage);
   }
 
   /// isWeakForLinker - Whether the definition of this global may be replaced at
@@ -170,7 +175,8 @@ public:
             Linkage == LinkOnceAnyLinkage ||
             Linkage == LinkOnceODRLinkage ||
             Linkage == CommonLinkage ||
-            Linkage == ExternalWeakLinkage);
+            Linkage == ExternalWeakLinkage ||
+            Linkage == LinkerPrivateWeakLinkage);
   }
 
   bool hasExternalLinkage() const { return isExternalLinkage(Linkage); }
@@ -187,6 +193,9 @@ public:
   bool hasInternalLinkage() const { return isInternalLinkage(Linkage); }
   bool hasPrivateLinkage() const { return isPrivateLinkage(Linkage); }
   bool hasLinkerPrivateLinkage() const { return isLinkerPrivateLinkage(Linkage); }
+  bool hasLinkerPrivateWeakLinkage() const {
+    return isLinkerPrivateWeakLinkage(Linkage);
+  }
   bool hasLocalLinkage() const { return isLocalLinkage(Linkage); }
   bool hasDLLImportLinkage() const { return isDLLImportLinkage(Linkage); }
   bool hasDLLExportLinkage() const { return isDLLExportLinkage(Linkage); }

lib/AsmParser/LLLexer.cpp

@@ -492,6 +492,7 @@ lltok::Kind LLLexer::LexIdentifier() {
 
   KEYWORD(private);
   KEYWORD(linker_private);
+  KEYWORD(linker_private_weak);
   KEYWORD(internal);
   KEYWORD(available_externally);
   KEYWORD(linkonce);

lib/AsmParser/LLParser.cpp

@@ -196,19 +196,20 @@ bool LLParser::ParseTopLevelEntities() {
     // optional leading prefixes, the production is:
     // GlobalVar ::= OptionalLinkage OptionalVisibility OptionalThreadLocal
     //               OptionalAddrSpace ('constant'|'global') ...
-    case lltok::kw_private :       // OptionalLinkage
-    case lltok::kw_linker_private: // OptionalLinkage
-    case lltok::kw_internal:       // OptionalLinkage
-    case lltok::kw_weak:           // OptionalLinkage
-    case lltok::kw_weak_odr:       // OptionalLinkage
-    case lltok::kw_linkonce:       // OptionalLinkage
-    case lltok::kw_linkonce_odr:   // OptionalLinkage
-    case lltok::kw_appending:      // OptionalLinkage
-    case lltok::kw_dllexport:      // OptionalLinkage
-    case lltok::kw_common:         // OptionalLinkage
-    case lltok::kw_dllimport:      // OptionalLinkage
-    case lltok::kw_extern_weak:    // OptionalLinkage
-    case lltok::kw_external: {     // OptionalLinkage
+    case lltok::kw_private:             // OptionalLinkage
+    case lltok::kw_linker_private:      // OptionalLinkage
+    case lltok::kw_linker_private_weak: // OptionalLinkage
+    case lltok::kw_internal:            // OptionalLinkage
+    case lltok::kw_weak:                // OptionalLinkage
+    case lltok::kw_weak_odr:            // OptionalLinkage
+    case lltok::kw_linkonce:            // OptionalLinkage
+    case lltok::kw_linkonce_odr:        // OptionalLinkage
+    case lltok::kw_appending:           // OptionalLinkage
+    case lltok::kw_dllexport:           // OptionalLinkage
+    case lltok::kw_common:              // OptionalLinkage
+    case lltok::kw_dllimport:           // OptionalLinkage
+    case lltok::kw_extern_weak:         // OptionalLinkage
+    case lltok::kw_external: {          // OptionalLinkage
       unsigned Linkage, Visibility;
       if (ParseOptionalLinkage(Linkage) ||
           ParseOptionalVisibility(Visibility) ||
@@ -629,7 +630,8 @@ bool LLParser::ParseAlias(const std::string &Name, LocTy NameLoc,
       Linkage != GlobalValue::WeakODRLinkage &&
       Linkage != GlobalValue::InternalLinkage &&
       Linkage != GlobalValue::PrivateLinkage &&
-      Linkage != GlobalValue::LinkerPrivateLinkage)
+      Linkage != GlobalValue::LinkerPrivateLinkage &&
+      Linkage != GlobalValue::LinkerPrivateWeakLinkage)
     return Error(LinkageLoc, "invalid linkage type for alias");
 
   Constant *Aliasee;
@@ -1013,11 +1015,13 @@ bool LLParser::ParseOptionalAttrs(unsigned &Attrs, unsigned AttrKind) {
 ///   ::= /*empty*/
 ///   ::= 'private'
 ///   ::= 'linker_private'
+///   ::= 'linker_private_weak'
 ///   ::= 'internal'
 ///   ::= 'weak'
 ///   ::= 'weak_odr'
 ///   ::= 'linkonce'
 ///   ::= 'linkonce_odr'
+///   ::= 'available_externally'
 ///   ::= 'appending'
 ///   ::= 'dllexport'
 ///   ::= 'common'
@@ -1030,6 +1034,9 @@ bool LLParser::ParseOptionalLinkage(unsigned &Res, bool &HasLinkage) {
   default:                       Res=GlobalValue::ExternalLinkage; return false;
   case lltok::kw_private:        Res = GlobalValue::PrivateLinkage;       break;
   case lltok::kw_linker_private: Res = GlobalValue::LinkerPrivateLinkage; break;
+  case lltok::kw_linker_private_weak:
+    Res = GlobalValue::LinkerPrivateWeakLinkage;
+    break;
   case lltok::kw_internal:       Res = GlobalValue::InternalLinkage;      break;
   case lltok::kw_weak:           Res = GlobalValue::WeakAnyLinkage;       break;
   case lltok::kw_weak_odr:       Res = GlobalValue::WeakODRLinkage;       break;
@@ -2704,6 +2711,7 @@ bool LLParser::ParseFunctionHeader(Function *&Fn, bool isDefine) {
     break;
   case GlobalValue::PrivateLinkage:
   case GlobalValue::LinkerPrivateLinkage:
+  case GlobalValue::LinkerPrivateWeakLinkage:
   case GlobalValue::InternalLinkage:
   case GlobalValue::AvailableExternallyLinkage:
   case GlobalValue::LinkOnceAnyLinkage:

lib/AsmParser/LLToken.h

@@ -37,9 +37,9 @@ namespace lltok {
     kw_declare, kw_define,
     kw_global,  kw_constant,
 
-    kw_private, kw_linker_private, kw_internal, kw_linkonce, kw_linkonce_odr,
-    kw_weak, kw_weak_odr, kw_appending, kw_dllimport, kw_dllexport, kw_common,
-    kw_available_externally,
+    kw_private, kw_linker_private, kw_linker_private_weak, kw_internal,
+    kw_linkonce, kw_linkonce_odr, kw_weak, kw_weak_odr, kw_appending,
+    kw_dllimport, kw_dllexport, kw_common, kw_available_externally,
     kw_default, kw_hidden, kw_protected,
     kw_extern_weak,
     kw_external, kw_thread_local,

lib/Bitcode/Reader/BitcodeReader.cpp

@@ -75,6 +75,7 @@ static GlobalValue::LinkageTypes GetDecodedLinkage(unsigned Val) {
   case 11: return GlobalValue::LinkOnceODRLinkage;
   case 12: return GlobalValue::AvailableExternallyLinkage;
   case 13: return GlobalValue::LinkerPrivateLinkage;
+  case 14: return GlobalValue::LinkerPrivateWeakLinkage;
   }
 }
 

lib/Bitcode/Writer/BitcodeWriter.cpp

@@ -313,6 +313,7 @@ static unsigned getEncodedLinkage(const GlobalValue *GV) {
   case GlobalValue::LinkOnceODRLinkage:         return 11;
   case GlobalValue::AvailableExternallyLinkage: return 12;
   case GlobalValue::LinkerPrivateLinkage:       return 13;
+  case GlobalValue::LinkerPrivateWeakLinkage:   return 14;
   }
 }
 

lib/CodeGen/AsmPrinter/AsmPrinter.cpp

@@ -200,6 +200,7 @@ void AsmPrinter::EmitLinkage(unsigned Linkage, MCSymbol *GVSym) const {
   case GlobalValue::WeakAnyLinkage:
   case GlobalValue::WeakODRLinkage:
   case GlobalValue::LinkerPrivateLinkage:
+  case GlobalValue::LinkerPrivateWeakLinkage:
     if (MAI->getWeakDefDirective() != 0) {
       // .globl _foo
       OutStreamer.EmitSymbolAttribute(GVSym, MCSA_Global);

lib/Target/CppBackend/CPPBackend.cpp

@@ -286,6 +286,8 @@ void CppWriter::printLinkageType(GlobalValue::LinkageTypes LT) {
     Out << "GlobalValue::PrivateLinkage"; break;
   case GlobalValue::LinkerPrivateLinkage:
     Out << "GlobalValue::LinkerPrivateLinkage"; break;
+  case GlobalValue::LinkerPrivateWeakLinkage:
+    Out << "GlobalValue::LinkerPrivateWeakLinkage"; break;
   case GlobalValue::AvailableExternallyLinkage:
     Out << "GlobalValue::AvailableExternallyLinkage "; break;
   case GlobalValue::LinkOnceAnyLinkage:

lib/Target/Mangler.cpp

@@ -180,7 +180,7 @@ void Mangler::getNameWithPrefix(SmallVectorImpl<char> &OutName,
   ManglerPrefixTy PrefixTy = Mangler::Default;
   if (GV->hasPrivateLinkage() || isImplicitlyPrivate)
     PrefixTy = Mangler::Private;
-  else if (GV->hasLinkerPrivateLinkage())
+  else if (GV->hasLinkerPrivateLinkage() || GV->hasLinkerPrivateWeakLinkage())
     PrefixTy = Mangler::LinkerPrivate;
   
   // If this global has a name, handle it simply.

lib/Target/XCore/AsmPrinter/XCoreAsmPrinter.cpp

@@ -138,7 +138,6 @@ void XCoreAsmPrinter::EmitGlobalVariable(const GlobalVariable *GV) {
     // FALL THROUGH
   case GlobalValue::InternalLinkage:
   case GlobalValue::PrivateLinkage:
-  case GlobalValue::LinkerPrivateLinkage:
     break;
   case GlobalValue::DLLImportLinkage:
     llvm_unreachable("DLLImport linkage is not supported by this target!");

lib/Transforms/IPO/MergeFunctions.cpp

@@ -535,6 +535,7 @@ static LinkageCategory categorize(const Function *F) {
   case GlobalValue::WeakAnyLinkage:
   case GlobalValue::WeakODRLinkage:
   case GlobalValue::ExternalWeakLinkage:
+  case GlobalValue::LinkerPrivateWeakLinkage:
     return ExternalWeak;
 
   case GlobalValue::ExternalLinkage:

lib/VMCore/AsmWriter.cpp

@@ -1419,6 +1419,9 @@ static void PrintLinkage(GlobalValue::LinkageTypes LT,
   case GlobalValue::ExternalLinkage: break;
   case GlobalValue::PrivateLinkage:       Out << "private ";        break;
   case GlobalValue::LinkerPrivateLinkage: Out << "linker_private "; break;
+  case GlobalValue::LinkerPrivateWeakLinkage:
+    Out << "linker_private_weak ";
+    break;
   case GlobalValue::InternalLinkage:      Out << "internal ";       break;
   case GlobalValue::LinkOnceAnyLinkage:   Out << "linkonce ";       break;
   case GlobalValue::LinkOnceODRLinkage:   Out << "linkonce_odr ";   break;

lib/VMCore/Core.cpp

@@ -1058,6 +1058,8 @@ LLVMLinkage LLVMGetLinkage(LLVMValueRef Global) {
     return LLVMPrivateLinkage;
   case GlobalValue::LinkerPrivateLinkage:
     return LLVMLinkerPrivateLinkage;
+  case GlobalValue::LinkerPrivateWeakLinkage:
+    return LLVMLinkerPrivateWeakLinkage;
   case GlobalValue::DLLImportLinkage:
     return LLVMDLLImportLinkage;
   case GlobalValue::DLLExportLinkage:
@@ -1108,6 +1110,9 @@ void LLVMSetLinkage(LLVMValueRef Global, LLVMLinkage Linkage) {
   case LLVMLinkerPrivateLinkage:
     GV->setLinkage(GlobalValue::LinkerPrivateLinkage);
     break;
+  case LLVMLinkerPrivateWeakLinkage:
+    GV->setLinkage(GlobalValue::LinkerPrivateWeakLinkage);
+    break;
   case LLVMDLLImportLinkage:
     GV->setLinkage(GlobalValue::DLLImportLinkage);
     break;

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

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

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

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

tools/llvm-nm/llvm-nm.cpp

@@ -89,7 +89,8 @@ static char TypeCharForSymbol(GlobalValue &GV) {
 static void DumpSymbolNameForGlobalValue(GlobalValue &GV) {
   // Private linkage and available_externally linkage don't exist in symtab.
   if (GV.hasPrivateLinkage() || GV.hasLinkerPrivateLinkage() ||
-      GV.hasAvailableExternallyLinkage()) return;
+      GV.hasLinkerPrivateWeakLinkage() || GV.hasAvailableExternallyLinkage())
+    return;
   
   const std::string SymbolAddrStr = "        "; // Not used yet...
   char TypeChar = TypeCharForSymbol(GV);