Overhaul my earlier submission due to feedback. It's a large patch, but most of

them are generic changes.

- Use the "fast" flag that's already being passed into the asm printers instead
  of shoving it into the DwarfWriter.

- Instead of calling "MI->getParent()->getParent()" for every MI, set the
  machine function when calling "runOnMachineFunction" in the asm printers.

llvm-svn: 65379