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

3 files changed, 14 insertions, 11 deletions

diff --git a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index ffccd9e2c0..fa9b777cd8 100644
--- a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -199,6 +199,7 @@ void AsmPrinter::EmitLinkage(unsigned Linkage, MCSymbol *GVSym) const {
   case GlobalValue::LinkOnceODRLinkage:
   case GlobalValue::WeakAnyLinkage:
   case GlobalValue::WeakODRLinkage:
+  case GlobalValue::LinkerWeakLinkage:
   case GlobalValue::LinkerPrivateLinkage:
     if (MAI->getWeakDefDirective() != 0) {
       // .globl _foo
@@ -1610,8 +1611,8 @@ MCSymbol *AsmPrinter::GetCPISymbol(unsigned CPID) const {
 }
 
 /// GetJTISymbol - Return the symbol for the specified jump table entry.
-MCSymbol *AsmPrinter::GetJTISymbol(unsigned JTID, bool isLinkerPrivate) const {
-  return MF->getJTISymbol(JTID, OutContext, isLinkerPrivate);
+MCSymbol *AsmPrinter::GetJTISymbol(unsigned JTID, bool PassToLinker) const {
+  return MF->getJTISymbol(JTID, OutContext, PassToLinker);
 }
 
 /// GetJTSetSymbol - Return the symbol for the specified jump table .set
diff --git a/lib/CodeGen/MachineFunction.cpp b/lib/CodeGen/MachineFunction.cpp
index a38c881982..c84c31ec10 100644
--- a/lib/CodeGen/MachineFunction.cpp
+++ b/lib/CodeGen/MachineFunction.cpp
@@ -410,17 +410,18 @@ unsigned MachineFunction::addLiveIn(unsigned PReg,
 }
 
 /// getJTISymbol - Return the MCSymbol for the specified non-empty jump table.
-/// If isLinkerPrivate is specified, an 'l' label is returned, otherwise a
-/// normal 'L' label is returned.
-MCSymbol *MachineFunction::getJTISymbol(unsigned JTI, MCContext &Ctx, 
-                                        bool isLinkerPrivate) const {
+/// If isLinkerPrivate or isLinkerWeak is specified, an 'l' label is returned,
+/// otherwise a normal 'L' label is returned.
+MCSymbol *MachineFunction::getJTISymbol(unsigned JTI, MCContext &Ctx,
+                                        bool PassToLinker) const {
   assert(JumpTableInfo && "No jump tables");
   
   assert(JTI < JumpTableInfo->getJumpTables().size() && "Invalid JTI!");
   const MCAsmInfo &MAI = *getTarget().getMCAsmInfo();
   
-  const char *Prefix = isLinkerPrivate ? MAI.getLinkerPrivateGlobalPrefix() :
-                                         MAI.getPrivateGlobalPrefix();
+  const char *Prefix = PassToLinker ?
+    MAI.getLinkerPrivateGlobalPrefix() :
+    MAI.getPrivateGlobalPrefix();
   SmallString<60> Name;
   raw_svector_ostream(Name)
     << Prefix << "JTI" << getFunctionNumber() << '_' << JTI;
diff --git a/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
index 71ad3fb6f9..56420539b7 100644
--- a/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ b/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -755,11 +755,12 @@ shouldEmitUsedDirectiveFor(const GlobalValue *GV, Mangler *Mang) const {
   /// the directive emitted (this occurs in ObjC metadata).
   if (!GV) return false;
 
-  // Check whether the mangled name has the "Private" or "LinkerPrivate" prefix.
+  // Check whether the mangled name has the "Private", "LinkerPrivate", or
+  // "LinkerWeak" prefix.
   if (GV->hasLocalLinkage() && !isa<Function>(GV)) {
     // FIXME: ObjC metadata is currently emitted as internal symbols that have
-    // \1L and \0l prefixes on them.  Fix them to be Private/LinkerPrivate and
-    // this horrible hack can go away.
+    // \1L and \1l prefixes on them.  Fix them to be Private / LinkerPrivate /
+    // LinkerWeak and this horrible hack can go away.
     MCSymbol *Sym = Mang->getSymbol(GV);
     if (Sym->getName()[0] == 'L' || Sym->getName()[0] == 'l')
       return false;