Implement (and document!) support for MnemonicAlias's to have Requires 
directives, allowing things like this:

def : MnemonicAlias<"pop", "popl">, Requires<[In32BitMode]>;
def : MnemonicAlias<"pop", "popq">, Requires<[In64BitMode]>;

Move the rest of the X86 MnemonicAliases over to the .td file.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@117830 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed