FYI: Removal of XXXRegisterClass from GenRegisterInfo.inc

In r155270, I removed code from TableGen that emitted XXXRegisterClass into GenRegisterInfo.inc. This value was just a const pointer to XXXRegClass. So all places that used XXXRegisterClass should be changed to &XXXRegisterClass. I already did the conversion for all targets in the tree so this is a notice to out of tree targets.

One of the most common place you might find this is setting up register classes in TargetLowering. For example,

addRegisterClass(MVT::i8, X86::GR8RegisterClass);
addRegisterClass(MVT::i16, X86::GR16RegisterClass);
addRegisterClass(MVT::i32, X86::GR32RegisterClass);

These should be changed to

addRegisterClass(MVT::i8, &X86::GR8RegClass);
addRegisterClass(MVT::i16, &X86::GR16RegClass);
addRegisterClass(MVT::i32, &X86::GR32RegClass);

Hopefully, this change won’t cause too much trouble.