Introduce new linkage types linkonce_odr, weak_odr, common_odr

and extern_weak_odr.  These are the same as the non-odr versions,
except that they indicate that the global will only be overridden
by an *equivalent* global.  In C, a function with weak linkage can
be overridden by a function which behaves completely differently.
This means that IP passes have to skip weak functions, since any
deductions made from the function definition might be wrong, since
the definition could be replaced by something completely different
at link time.   This is not allowed in C++, thanks to the ODR
(One-Definition-Rule): if a function is replaced by another at
link-time, then the new function must be the same as the original
function.  If a language knows that a function or other global can
only be overridden by an equivalent global, it can give it the
weak_odr linkage type, and the optimizers will understand that it
is alright to make deductions based on the function body.  The
code generators on the other hand map weak and weak_odr linkage
to the same thing.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@66339 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 14 insertions, 4 deletions

diff --git a/include/llvm-c/Core.h b/include/llvm-c/Core.h
index 6016ac61b5..5d8cff414f 100644
--- a/include/llvm-c/Core.h
+++ b/include/llvm-c/Core.h
@@ -115,16 +115,26 @@ typedef enum {
 
 typedef enum {
   LLVMExternalLinkage,    /**< Externally visible function */
-  LLVMLinkOnceLinkage,    /**< Keep one copy of function when linking (inline)*/
-  LLVMWeakLinkage,        /**< Keep one copy of function when linking (weak) */
+  LLVMLinkOnceAnyLinkage, /**< Keep one copy of function when linking (inline)*/
+  LLVMLinkOnceODRLinkage, /**< Same, but only replaced by something
+                            equivalent. */
+  LLVMWeakAnyLinkage,     /**< Keep one copy of function when linking (weak) */
+  LLVMWeakODRLinkage,     /**< Same, but only replaced by something
+                            equivalent. */
   LLVMAppendingLinkage,   /**< Special purpose, only applies to global arrays */
   LLVMInternalLinkage,    /**< Rename collisions when linking (static
                                functions) */
+  LLVMPrivateLinkage,     /**< Like Internal, but omit from symbol table */
   LLVMDLLImportLinkage,   /**< Function to be imported from DLL */
   LLVMDLLExportLinkage,   /**< Function to be accessible from DLL */
-  LLVMExternalWeakLinkage,/**< ExternalWeak linkage description */
-  LLVMGhostLinkage        /**< Stand-in functions for streaming fns from
+  LLVMExternalWeakAnyLinkage,/**< ExternalWeak linkage description */
+  LLVMExternalWeakODRLinkage,/**< Same, but only replaced by something
+                               equivalent. */
+  LLVMGhostLinkage,       /**< Stand-in functions for streaming fns from
                                bitcode */
+  LLVMCommonAnyLinkage,   /**< Tentative definitions */
+  LLVMCommonODRLinkage    /**< Same, but only replaced by something
+                            equivalent. */
 } LLVMLinkage;
 
 typedef enum {