[PatternMatch] add special-case uaddo matching for increment-by-one

This is the most important uaddo problem mentioned in PR31754:
https://bugs.llvm.org/show_bug.cgi?id=31754

We were failing to match the canonicalized pattern when it's an 'add 1' operation.
Pattern matching, however, shouldn't assume that we have canonicalized IR, so we 
match 4 commuted variants of uaddo.

There's also a test with a crazy type to show that the existing CGP transform 
based on this matcher is not limited by target legality checks, but that's a
different problem.

Differential Revision: https://reviews.llvm.org/D57516

llvm-svn: 352766

0 files changed, 0 insertions, 0 deletions