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/OptimizePHIs.cpp

@@ -56,11 +56,10 @@ namespace {
 }
 
 char OptimizePHIs::ID = 0;
+char &llvm::OptimizePHIsID = OptimizePHIs::ID;
 INITIALIZE_PASS(OptimizePHIs, "opt-phis",
                 "Optimize machine instruction PHIs", false, false)
 
-FunctionPass *llvm::createOptimizePHIsPass() { return new OptimizePHIs(); }
-
 bool OptimizePHIs::runOnMachineFunction(MachineFunction &Fn) {
   MRI = &Fn.getRegInfo();
   TII = Fn.getTarget().getInstrInfo();