Add a special streamer to libLTO that just records symbols definitions and

uses.

The result produced by the streamer is used to give the linker more accurate
information and to add to llvm.compiler.used. The second improvement removes
the need for the user to add __attribute__((used)) to functions only used in
inline asm. The first one lets us build firefox with LTO on Darwin :-)

llvm-svn: 126830

1 files changed, 6 insertions, 3 deletions

diff --git a/llvm/lib/VMCore/AsmWriter.cpp b/llvm/lib/VMCore/AsmWriter.cpp
index cbc874a53f6..ff6084d8a8b 100644
--- a/llvm/lib/VMCore/AsmWriter.cpp
+++ b/llvm/lib/VMCore/AsmWriter.cpp
@@ -1338,9 +1338,12 @@ void AssemblyWriter::printModule(const Module *M) {
       CurPos = NewLine+1;
       NewLine = Asm.find_first_of('\n', CurPos);
     }
-    Out << "module asm \"";
-    PrintEscapedString(std::string(Asm.begin()+CurPos, Asm.end()), Out);
-    Out << "\"\n";
+    std::string rest(Asm.begin()+CurPos, Asm.end());
+    if (!rest.empty()) {
+      Out << "module asm \"";
+      PrintEscapedString(rest, Out);
+      Out << "\"\n";
+    }
   }
 
   // Loop over the dependent libraries and emit them.