Use ELF function index to distinguish generated functions.

We replaced LLVMLongName and LLVMStubName with ElfFuncName,
and we are using the simple name: Art0, Art1, ..., ArtN,
as the function name of every generated functions.  This
gives us 3 benefits:

1. We can avoid the ambiguous function name returned by
   LLVMLongName() in some special situation.

2. We don't need to have the art::Method object during
   the executable linking procedure.  Besides, this will
   make bootstrapping easier.

3. Reduce the size of the ELF executable, since we don't
   have to save a long function name, which usually contains
   more than 30 characters.

Change-Id: Ib698062b272458e847ad5545d7acf33a4dc9eb85
diff --git a/src/compiler_llvm/method_compiler.cc b/src/compiler_llvm/method_compiler.cc
index 8b1cef6..57dbf15 100644
--- a/src/compiler_llvm/method_compiler.cc
+++ b/src/compiler_llvm/method_compiler.cc
@@ -67,7 +67,7 @@
     basic_blocks_(code_item_->insns_size_in_code_units_),
     basic_block_landing_pads_(code_item_->tries_size_, NULL),
     basic_block_unwind_(NULL), basic_block_unreachable_(NULL),
-    shadow_frame_(NULL) {
+    shadow_frame_(NULL), elf_func_idx_(cunit_->AcquireUniqueElfFuncIndex()) {
 }
 
 
@@ -78,7 +78,7 @@
 
 void MethodCompiler::CreateFunction() {
   // LLVM function name
-  std::string func_name(LLVMLongName(method_));
+  std::string func_name(ElfFuncName(elf_func_idx_));
 
   // Get function type
   llvm::FunctionType* func_type =
@@ -3773,7 +3773,8 @@
   // Thus, we got our magic number 9.
 
   return new CompiledMethod(cunit_->GetInstructionSet(),
-                            cunit_->GetElfIndex());
+                            cunit_->GetElfIndex(),
+                            elf_func_idx_);
 }