Restore LLVMLinkModules C API until it is properly deprecated.

Add the enum "LLVMLinkerMode" back for backwards-compatibility and add the
linker mode parameter back to the "LLVMLinkModules" function. The paramter is
ignored and has no effect.

Patch provided by: Filip Pizlo
Reviewed by: Rafael and Sean

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230988 91177308-0d34-0410-b5e6-96231b3b80d8

bindings/go/llvm/linker.go

@@ -22,7 +22,7 @@ import "errors"
 
 func LinkModules(Dest, Src Module) error {
 	var cmsg *C.char
-	failed := C.LLVMLinkModules(Dest.C, Src.C, 0, &cmsg)
+	failed := C.LLVMLinkModules(Dest.C, Src.C, C.LLVMLinkerDestroySource, &cmsg)
 	if failed != 0 {
 		err := errors.New(C.GoString(cmsg))
 		C.LLVMDisposeMessage(cmsg)

include/llvm-c/Linker.h

@@ -20,13 +20,23 @@
 extern "C" {
 #endif
 
+/* This enum is provided for backwards-compatibility only. It has no effect. */
+typedef enum {
+  LLVMLinkerDestroySource = 0, /* This is the default behavior. */
+  LLVMLinkerPreserveSource_Removed = 1 /* This option has been deprecated and
+                                          should not be used. */
+} LLVMLinkerMode;
+
 /* Links the source module into the destination module, taking ownership
  * of the source module away from the caller. Optionally returns a
  * human-readable description of any errors that occurred in linking.
  * OutMessage must be disposed with LLVMDisposeMessage. The return value
- * is true if an error occurred, false otherwise. */
+ * is true if an error occurred, false otherwise.
+ *
+ * Note that the linker mode parameter \p Unused is no longer used, and has
+ * no effect. */
 LLVMBool LLVMLinkModules(LLVMModuleRef Dest, LLVMModuleRef Src,
-                         unsigned Unused, char **OutMessage);
+                         LLVMLinkerMode Unused, char **OutMessage);
 
 #ifdef __cplusplus
 }

lib/Linker/LinkModules.cpp

@@ -1777,7 +1777,7 @@ bool Linker::LinkModules(Module *Dest, Module *Src) {
 //===----------------------------------------------------------------------===//
 
 LLVMBool LLVMLinkModules(LLVMModuleRef Dest, LLVMModuleRef Src,
-                         unsigned Unused, char **OutMessages) {
+                         LLVMLinkerMode Unused, char **OutMessages) {
   Module *D = unwrap(Dest);
   std::string Message;
   raw_string_ostream Stream(Message);