[InstCombine] Fold icmp eq/ne (and %x, signbit), 0 -> %x s>=/s< 0 earlier

Summary:
To generate simplified IR, make sure fold
```
  (X & signbit) ==/!= 0) -> X s>=/s< 0;
```
is scheduled before fold
```
  ((X << Y) & C) == 0 -> (X & (C >> Y)) == 0.
```

https://rise4fun.com/Alive/fbdh

Reviewers: lebedev.ri, efriedma, spatel, craig.topper

Reviewed By: lebedev.ri

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D63026

llvm-svn: 363845