[InstCombine] canonicalize more unsigned saturated add with 'not'

[InstCombine] canonicalize more unsigned saturated add with 'not'

Yet another pattern variation suggested by:
https://bugs.llvm.org/show_bug.cgi?id=14613

There are 8 more potential commuted patterns here on top of the
8 that were already handled (rL354221, rL354276, rL354393).
We have the obvious commute of the 'add' + commute of the cmp
predicate/operands (ugt/ult) + commute of the select operands:

Name: base
%notx = xor i32 %x, -1
%a = add i32 %notx, %y
%c = icmp ult i32 %x, %y
%r = select i1 %c, i32 -1, i32 %a
=>
%c2 = icmp ult i32 %a, %y
%r = select i1 %c2, i32 -1, i32 %a

Name: ugt
%notx = xor i32 %x, -1
%a = add i32 %notx, %y
%c = icmp ugt i32 %y, %x
%r = select i1 %c, i32 -1, i32 %a
=>
%c2 = icmp ult i32 %a, %y
%r = select i1 %c2, i32 -1, i32 %a

Name: commute select
%notx = xor i32 %x, -1
%a = add i32 %notx, %y
%c = icmp ult i32 %y, %x
%r = select i1 %c, i32 %a, i32 -1
=>
%c2 = icmp ult i32 %a, %y
%r = select i1 %c2, i32 -1, i32 %a

Name: ugt + commute select
%notx = xor i32 %x, -1
%a = add i32 %notx, %y
%c = icmp ugt i32 %x, %y
%r = select i1 %c, i32 %a, i32 -1
=>
%c2 = icmp ult i32 %a, %y
%r = select i1 %c2, i32 -1, i32 %a

https://rise4fun.com/Alive/den

llvm-svn: 354887