The RegisterInfo descriptors for the convenience registers can specify an...

The RegisterInfo descriptors for the convenience registers can specify an offset to be added to the offset as derived from
the value_regs field, which is useful for future expansion purposes.  As of now, we have:

    calculated_offset_of_eax = offset_of_rax + (offset_of_eax_from_the_descriptor which is 0)

llvm-svn: 157275