Change LLVM bitcode linking to use tree reduction to scale better

llvm/include/llvm-c/lto.h

 /*===-- llvm-c/lto.h - LTO Public C Interface ---------------------*- C -*-===*\
 |*                                                                            *|
 |*                     The LLVM Compiler Infrastructure                       *|
 |*                                                                            *|
 |* This file is distributed under the University of Illinois Open Source      *|
 |* License. See LICENSE.TXT for details.                                      *|
 |*                                                                            *|
 |*===----------------------------------------------------------------------===*|
 |*                                                                            *|
 |* This header provides public interface to an abstract link time optimization*|
@@ skipping 241 matching lines @@
 
 
 
 /**
  * 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).
  */
 extern bool
 lto_codegen_add_module(lto_code_gen_t cg, lto_module_t mod);
 
+/* @LOCALMOD-BEGIN */
+/**
+ * Add an object module to the set of modules for which code will be generated.
+ * This does not merge the module immediately, unlike lto_codegen_add_module.
+ * It will hold onto the module until the user calls
+ * lto_codegen_link_gathered_modules_and_dispose().  The lto_module_t
+ * should now by owned by the lto_code_gen_t, and will be freed when
+ * the link is done.
+ */
+extern bool
+lto_codegen_gather_module_for_link(lto_code_gen_t cg, lto_module_t mod);
 
+/**
+ * Merges modules that are part of the set of modules gathered by
+ * lto_codegen_gather_module_for_link(), and the also destroys the modules
+ * as lto_module_dispose() would.
+ */
+extern bool
+lto_codegen_link_gathered_modules_and_dispose(lto_code_gen_t cg);
+/* @LOCALMOD-END*/
 
 /**
  * Sets if debug info should be generated.
  * Returns true on error (check lto_get_error_message() for details).
  */
 extern bool
 lto_codegen_set_debug_model(lto_code_gen_t cg, lto_debug_model);
 
 
 /**
@@ skipping 118 matching lines @@
 
 #ifdef __cplusplus
 }
 #endif
 
 /**
  * @}
  */
 
 #endif