Revert 224782: "Finish removing DestroySource."

Filip Pizlo pointed out that this changes the C API.

It's too late in the release process to figure out how we want to
handle this. Reverting the patch is essentially a way of buying time:
we don't change the API at the source level for now, we're not
trying to fix it with a last-minute patch with a risk of unintended
effects, and we preserve our options for fixing this in 3.6.1.

This is not ideal, but I think it's the best compromise at this stage.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_36@230431 91177308-0d34-0410-b5e6-96231b3b80d8

bindings/go/llvm/linker.go

@@ -20,9 +20,16 @@ package llvm
 import "C"
 import "errors"
 
-func LinkModules(Dest, Src Module) error {
+type LinkerMode C.LLVMLinkerMode
+
+const (
+	LinkerDestroySource  = C.LLVMLinkerDestroySource
+	LinkerPreserveSource = C.LLVMLinkerPreserveSource
+)
+
+func LinkModules(Dest, Src Module, Mode LinkerMode) error {
 	var cmsg *C.char
-	failed := C.LLVMLinkModules(Dest.C, Src.C, 0, &cmsg)
+	failed := C.LLVMLinkModules(Dest.C, Src.C, C.LLVMLinkerMode(Mode), &cmsg)
 	if failed != 0 {
 		err := errors.New(C.GoString(cmsg))
 		C.LLVMDisposeMessage(cmsg)

bindings/ocaml/linker/linker_ocaml.c

@@ -23,11 +23,11 @@
 
 void llvm_raise(value Prototype, char *Message);
 
-/* llmodule -> llmodule -> unit */
-CAMLprim value llvm_link_modules(LLVMModuleRef Dst, LLVMModuleRef Src) {
+/* llmodule -> llmodule -> Mode.t -> unit */
+CAMLprim value llvm_link_modules(LLVMModuleRef Dst, LLVMModuleRef Src, value Mode) {
   char* Message;
 
-  if (LLVMLinkModules(Dst, Src, 0, &Message))
+  if (LLVMLinkModules(Dst, Src, Int_val(Mode), &Message))
     llvm_raise(*caml_named_value("Llvm_linker.Error"), Message);
 
   return Val_unit;

bindings/ocaml/linker/llvm_linker.ml

@@ -11,5 +11,11 @@ exception Error of string
 
 let () = Callback.register_exception "Llvm_linker.Error" (Error "")
 
-external link_modules : Llvm.llmodule -> Llvm.llmodule -> unit
+module Mode = struct
+  type t =
+  | DestroySource
+  | PreserveSource
+end
+
+external link_modules : Llvm.llmodule -> Llvm.llmodule -> Mode.t -> unit
                       = "llvm_link_modules"

bindings/ocaml/linker/llvm_linker.mli

@@ -14,6 +14,13 @@
 
 exception Error of string
 
+(** Linking mode. *)
+module Mode : sig
+  type t =
+  | DestroySource
+  | PreserveSource
+end
+
 (** [link_modules dst src mode] links [src] into [dst], raising [Error]
     if the linking fails. *)
-val link_modules : Llvm.llmodule -> Llvm.llmodule -> unit
+val link_modules : Llvm.llmodule -> Llvm.llmodule -> Mode.t -> unit

docs/ReleaseNotes.rst

@@ -383,6 +383,9 @@ The PreserveSource linker mode was removed
 
 It was fairly broken and was removed.
 
+The mode is currently still available in the C API for source
+compatibility, but it doesn't have any effect.
+
 
 Garbage Collection
 ------------------

include/llvm-c/Linker.h

@@ -20,13 +20,21 @@
 extern "C" {
 #endif
 
+
+/* Note: LLVMLinkerPreserveSource has no effect. */
+typedef enum {
+  LLVMLinkerDestroySource = 0, /* Allow source module to be destroyed. */
+  LLVMLinkerPreserveSource = 1 /* Preserve the source module. */
+} 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. */
 LLVMBool LLVMLinkModules(LLVMModuleRef Dest, LLVMModuleRef Src,
-                         unsigned Unused, char **OutMessage);
+                         LLVMLinkerMode Mode, char **OutMessage);
 
 #ifdef __cplusplus
 }

lib/Linker/LinkModules.cpp

@@ -1749,7 +1749,7 @@ bool Linker::LinkModules(Module *Dest, Module *Src) {
 //===----------------------------------------------------------------------===//
 
 LLVMBool LLVMLinkModules(LLVMModuleRef Dest, LLVMModuleRef Src,
-                         unsigned Unused, char **OutMessages) {
+                         LLVMLinkerMode Mode, char **OutMessages) {
   Module *D = unwrap(Dest);
   std::string Message;
   raw_string_ostream Stream(Message);

test/Bindings/OCaml/linker.ml

@@ -45,7 +45,7 @@ let test_linker () =
 
   let m1 = make_module "one"
   and m2 = make_module "two" in
-  link_modules m1 m2;
+  link_modules m1 m2 Mode.DestroySource;
   dispose_module m1;
 
   let m1 = make_module "one"