Redo the arithmetic with overflow architecture. I was changing the semantics of

Redo the arithmetic with overflow architecture. I was changing the semantics of
ISD::ADD to emit an implicit EFLAGS. This was horribly broken. Instead, replace
the intrinsic with an ISD::SADDO node. Then custom lower that into an
X86ISD::ADD node with a associated SETCC that checks the correct condition code
(overflow or carry). Then that gets lowered into the correct X86::ADDOvf
instruction.

Similar for SUB and MUL instructions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60915 91177308-0d34-0410-b5e6-96231b3b80d8