[CodeGenPrepare] Move CodeGenPrepare into lib/CodeGen.

CodeGenPrepare uses extensively TargetLowering which is part of libLLVMCodeGen.
This is a layer violation which would introduce eventually a dependence on
CodeGen in ScalarOpts.

Move CodeGenPrepare into libLLVMCodeGen to avoid that.

Follow-up of <rdar://problem/15519855>


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201912 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/CodeGen.cpp

@@ -22,6 +22,7 @@ using namespace llvm;
 void llvm::initializeCodeGen(PassRegistry &Registry) {
   initializeBasicTTIPass(Registry);
   initializeBranchFolderPassPass(Registry);
+  initializeCodeGenPreparePass(Registry);
   initializeDeadMachineInstructionElimPass(Registry);
   initializeEarlyIfConverterPass(Registry);
   initializeExpandPostRAPass(Registry);