Add plumbing for the `linker_private' linkage type. This type is meant for

"private" symbols which the assember shouldn't strip, but which the linker may
remove after evaluation. This is mostly useful for Objective-C metadata.

This is plumbing, so we don't have a use of it yet. More to come, etc.

llvm-svn: 76385

3 files changed, 28 insertions, 11 deletions

diff --git a/llvm/include/llvm-c/Core.h b/llvm/include/llvm-c/Core.h
index 71e71a9c998..5d4b091ece3 100644
--- a/llvm/include/llvm-c/Core.h
+++ b/llvm/include/llvm-c/Core.h
@@ -141,6 +141,7 @@ typedef enum {
   LLVMInternalLinkage,    /**< Rename collisions when linking (static
                                functions) */
   LLVMPrivateLinkage,     /**< Like Internal, but omit from symbol table */
+  LLVMLinkerPrivateLinkage, /**< Like Private, but linker removes. */
   LLVMDLLImportLinkage,   /**< Function to be imported from DLL */
   LLVMDLLExportLinkage,   /**< Function to be accessible from DLL */
   LLVMExternalWeakLinkage,/**< ExternalWeak linkage description */
diff --git a/llvm/include/llvm/GlobalValue.h b/llvm/include/llvm/GlobalValue.h
index 0df7ababed7..b897f9f6bba 100644
--- a/llvm/include/llvm/GlobalValue.h
+++ b/llvm/include/llvm/GlobalValue.h
@@ -37,13 +37,14 @@ public:
     WeakAnyLinkage,     ///< Keep one copy of named function when linking (weak)
     WeakODRLinkage,     ///< Same, but only replaced by something equivalent.
     AppendingLinkage,   ///< Special purpose, only applies to global arrays
-    InternalLinkage,    ///< Rename collisions when linking (static functions)
-    PrivateLinkage,     ///< Like Internal, but omit from symbol table
+    InternalLinkage,    ///< Rename collisions when linking (static functions).
+    PrivateLinkage,     ///< Like Internal, but omit from symbol table.
+    LinkerPrivateLinkage, ///< Like Private, but linker removes.
     DLLImportLinkage,   ///< Function to be imported from DLL
-    DLLExportLinkage,   ///< Function to be accessible from DLL
-    ExternalWeakLinkage,///< ExternalWeak linkage description
-    GhostLinkage,       ///< Stand-in functions for streaming fns from BC files
-    CommonLinkage       ///< Tentative definitions
+    DLLExportLinkage,   ///< Function to be accessible from DLL.
+    ExternalWeakLinkage,///< ExternalWeak linkage description.
+    GhostLinkage,       ///< Stand-in functions for streaming fns from BC files.
+    CommonLinkage       ///< Tentative definitions.
   };
 
   /// @brief An enumeration for the kinds of visibility of global values.
@@ -123,8 +124,10 @@ public:
   bool hasAppendingLinkage() const { return Linkage == AppendingLinkage; }
   bool hasInternalLinkage() const { return Linkage == InternalLinkage; }
   bool hasPrivateLinkage() const { return Linkage == PrivateLinkage; }
+  bool hasLinkerPrivateLinkage() const { return Linkage==LinkerPrivateLinkage; }
   bool hasLocalLinkage() const {
-    return Linkage == InternalLinkage || Linkage == PrivateLinkage;
+    return hasInternalLinkage() || hasPrivateLinkage() ||
+      hasLinkerPrivateLinkage();
   }
   bool hasDLLImportLinkage() const { return Linkage == DLLImportLinkage; }
   bool hasDLLExportLinkage() const { return Linkage == DLLExportLinkage; }
diff --git a/llvm/include/llvm/Support/Mangler.h b/llvm/include/llvm/Support/Mangler.h
index e04245dc2b5..416f382bef4 100644
--- a/llvm/include/llvm/Support/Mangler.h
+++ b/llvm/include/llvm/Support/Mangler.h
@@ -25,6 +25,14 @@ class Value;
 class GlobalValue;
 
 class Mangler {
+public:
+  enum ManglerPrefixTy {
+    DefaultPrefixTy,       ///< Emit default string before each symbol.
+    PrivatePrefixTy,       ///< Emit "private" prefix before each symbol.
+    LinkerPrivatePrefixTy  ///< Emit "linker private" prefix before each symbol.
+  };
+
+private:
   /// Prefix - This string is added to each symbol that is emitted, unless the
   /// symbol is marked as not needing this prefix.
   const char *Prefix;
@@ -33,6 +41,10 @@ class Mangler {
   /// linkage.
   const char *PrivatePrefix;
 
+  /// LinkerPrivatePrefix - This string is emitted before each symbol with
+  /// "linker_private" linkage.
+  const char *LinkerPrivatePrefix;
+
   /// UseQuotes - If this is set, the target accepts global names in quotes,
   /// e.g. "foo bar" is a legal name.  This syntax is used instead of escaping
   /// the space character.  By default, this is false.
@@ -50,12 +62,13 @@ class Mangler {
 
   /// AcceptableChars - This bitfield contains a one for each character that is
   /// allowed to be part of an unmangled name.
-  unsigned AcceptableChars[256/32];
-public:
+  unsigned AcceptableChars[256 / 32];
 
+public:
   // Mangler ctor - if a prefix is specified, it will be prepended onto all
   // symbols.
-  Mangler(Module &M, const char *Prefix = "", const char *privatePrefix = "");
+  Mangler(Module &M, const char *Prefix = "", const char *privatePrefix = "",
+          const char *linkerPrivatePrefix = "");
 
   /// setUseQuotes - If UseQuotes is set to true, this target accepts quoted
   /// strings for assembler labels.
@@ -90,7 +103,7 @@ public:
   /// from getValueName.
   ///
   std::string makeNameProper(const std::string &x,
-                             bool hasPrivateLinkage = false);
+                             ManglerPrefixTy PrefixTy = DefaultPrefixTy);
 };
 
 } // End llvm namespace