[InstSimplify] Simplify uadd/sadd/umul/smul with overflow intrinsics when the...

[InstSimplify] Simplify uadd/sadd/umul/smul with overflow intrinsics when the Zero or Undef is on the LHS.

Summary: This code was migrated from InstCombine a few years ago. InstCombine had nearby code that would move Constants to the RHS for these, but InstSimplify doesn't have such code on this path.

Reviewers: spatel, majnemer, davide

Reviewed By: spatel

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D33473

llvm-svn: 303774