[NFC][InstSimplify] Some tests for dropping null check after...

[NFC][InstSimplify] Some tests for dropping null check after uadd.with.overflow of non-null (PR43246)

https://rise4fun.com/Alive/WRzq

Name: C <= Y && Y != 0  -->  C <= Y  iff C != 0
Pre: C != 0
  %y_is_nonnull = icmp ne i64 %y, 0
  %no_overflow = icmp ule i64 C, %y
  %r = and i1 %y_is_nonnull, %no_overflow
=>
  %r = %no_overflow

Name: C <= Y || Y != 0  -->  Y != 0  iff C != 0
Pre: C != 0
  %y_is_nonnull = icmp ne i64 %y, 0
  %no_overflow = icmp ule i64 C, %y
  %r = or i1 %y_is_nonnull, %no_overflow
=>
  %r = %y_is_nonnull

Name: C > Y || Y == 0  -->  C > Y  iff C != 0
Pre: C != 0
  %y_is_null = icmp eq i64 %y, 0
  %overflow = icmp ugt i64 C, %y
  %r = or i1 %y_is_null, %overflow
=>
  %r = %overflow

Name: C > Y && Y == 0  -->  Y == 0  iff C != 0
Pre: C != 0
  %y_is_null = icmp eq i64 %y, 0
  %overflow = icmp ugt i64 C, %y
  %r = and i1 %y_is_null, %overflow
=>
  %r = %y_is_null

https://bugs.llvm.org/show_bug.cgi?id=43246

llvm-svn: 371339