Change LLVM bitcode linking to use tree reduction to scale better

llvm/tools/llc/llc.cpp

 //===-- llc.cpp - Implement the LLVM Native Code Generator ----------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This is the llc code generator driver. It provides a convenient
@@ skipping 692 matching lines @@
   Out->keep();
 #endif
 
   // @LOCALMOD-BEGIN
   // Write out the metadata.
   //
   // We need to ensure that intrinsic prototypes are available, in case
   // we have a NeededRecord for one of them.
   // They may have been eliminated by the StripDeadPrototypes pass,
   // or some other pass that is unaware of NeededRecords / IntrinsicLowering.
-  IntrinsicLowering IL(*target->getTargetData());
-  IL.AddPrototypes(*M);
+  if (!MetadataTextFilename.empty()) {
+    IntrinsicLowering IL(*target->getTargetData());
+    IL.AddPrototypes(*M);
 
-  if (!MetadataTextFilename.empty()) {
     int err = WriteTextMetadataFile(*M.get(), TheTriple);
     if (err != 0)
       return err;
   }
   // @LOCALMOD-END
 
   return 0;
 }
 
 #if !defined(NACL_SRPC)
 int
 main (int argc, char **argv) {
   return llc_main(argc, argv);
 }
 #else
 // main() is in nacl_file.cpp.
 #endif