cases due to an isel deficiency already noted in
lib/Target/X86/README.txt, but they can be matched in this fold-call.ll
testcase, for example.
This is interesting mainly because it exposes a tricky tblgen bug;
tblgen was incorrectly computing the starting index for variable_ops
in the case of a complex pattern.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@51706 91177308-0d34-0410-b5e6-96231b3b80d8
