[CodeGen] Handle vector UADDO, SADDO, USUBO, SSUBO

This is part of https://bugs.llvm.org/show_bug.cgi?id=40442.

Vector legalization is implemented for the add/sub overflow opcodes.
UMULO/SMULO are also handled as far as legalization is concerned, but
they don't support vector expansion yet (so no tests for them).

The vector result widening implementation is suboptimal, because it
could result in a legalization loop.

Differential Revision: https://reviews.llvm.org/D57639

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@353464 91177308-0d34-0410-b5e6-96231b3b80d8
13 files changed