What host triple should I be using to specifically target x86_64 /
Win64? I notice there is no Win64 in the OSType enum, but there is
Win32. And yet I know llvm can target Win64, right?
Eric,
"x86_64-(pc)-win32" on ToT.
AFAIK no one cares vendor on windows.
We can know, to ask llvm::Triple, (OS == win32 && (arch == x86 || arch
== x86_64)).
I don't understand why do you need to distinguish Windows x64 with OSType.
(In contrast, I got rid of "-mingw64" and integrated to "-mingw32".)
Please let me know your matters.
I suppose "Win32" would not present "on 32bit" any more, like a
synonym "Windows NT API". 
...Takumi