Codegen pass definition cleanup. No functionality.

Moving toward a uniform style of pass definition to allow easier target configuration.
Globally declare Pass ID.
Globally declare pass initializer.
Use INITIALIZE_PASS consistently.
Add a call to the initializer from CodeGen.cpp.
Remove redundant "createPass" functions and "getPassName" methods.

While cleaning up declarations, cleaned up comments (sorry for large diff).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@150100 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/TailDuplication.cpp

@@ -74,7 +74,6 @@ namespace {
       MachineFunctionPass(ID), PreRegAlloc(false) {}
 
     virtual bool runOnMachineFunction(MachineFunction &MF);
-    virtual const char *getPassName() const { return "Tail Duplication"; }
 
   private:
     void AddSSAUpdateEntry(unsigned OrigReg, unsigned NewReg,
@@ -118,9 +117,10 @@ namespace {
   char TailDuplicatePass::ID = 0;
 }
 
-FunctionPass *llvm::createTailDuplicatePass() {
-  return new TailDuplicatePass();
-}
+char &llvm::TailDuplicateID = TailDuplicatePass::ID;
+
+INITIALIZE_PASS(TailDuplicatePass, "tailduplication", "Tail Duplication",
+                false, false)
 
 bool TailDuplicatePass::runOnMachineFunction(MachineFunction &MF) {
   TII = MF.getTarget().getInstrInfo();