Change LLVM bitcode linking to use tree reduction to scale better

llvm/tools/lto/lto.cpp

 //===-lto.cpp - LLVM Link Time Optimizer ----------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements the Link Time Optimization library. This library is
@@ skipping 187 matching lines @@
   delete cg;
 }
 
 /// lto_codegen_add_module - Add an object module to the set of modules for
 /// which code will be generated. Returns true on error (check
 /// lto_get_error_message() for details).
 bool lto_codegen_add_module(lto_code_gen_t cg, lto_module_t mod) {
   return cg->addModule(mod, sLastErrorString);
 }
 
+// @LOCALMOD-BEGIN
+bool lto_codegen_gather_module_for_link(lto_code_gen_t cg, lto_module_t mod) {
+  return cg->gatherModuleForLinking(mod);
+}
+
+bool lto_codegen_link_gathered_modules_and_dispose(lto_code_gen_t cg) {
+  return cg->linkGatheredModulesAndDispose(sLastErrorString);
+}
+// @LOCALMOD-END
+
 /// lto_codegen_set_debug_model - Sets what if any format of debug info should
 /// be generated. Returns true on error (check lto_get_error_message() for
 /// details).
 bool lto_codegen_set_debug_model(lto_code_gen_t cg, lto_debug_model debug) {
   return cg->setDebugInfo(debug, sLastErrorString);
 }
 
 /// lto_codegen_set_pic_model - Sets what code model to generated. Returns true
 /// on error (check lto_get_error_message() for details).
 bool lto_codegen_set_pic_model(lto_code_gen_t cg, lto_codegen_model model) {
@@ skipping 118 matching lines @@
 /// error.
 bool lto_codegen_compile_to_file(lto_code_gen_t cg, const char **name) {
   return cg->compile_to_file(name, sLastErrorString);
 }
 
 /// lto_codegen_debug_options - Used to pass extra options to the code
 /// generator.
 void lto_codegen_debug_options(lto_code_gen_t cg, const char *opt) {
   cg->setCodeGenDebugOptions(opt);
 }
-