and use it in x86 address mode folding. Also, make
getRegForValue return 0 for illegal types even if it has a
ValueMap for them, because Argument values are put in the
ValueMap. This fixes PR3181.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60696 91177308-0d34-0410-b5e6-96231b3b80d8