[CodeGen] [SelectionDAG] More efficient code for X % C == 0 (UREM case) (try 2)

[CodeGen] [SelectionDAG] More efficient code for X % C == 0 (UREM case) (try 2)

Summary:
I'm submitting a new revision since i don't understand how to reclaim/reopen/take over the existing one, D50222.
There is no such action in "Add Action" menu...
Original patch D50222 by @hermord (Dmytro Shynkevych)

This implements an optimization described in Hacker's Delight 10-17: when `C` is constant,
the result of `X % C == 0` can be computed more cheaply without actually calculating the remainder.
The motivation is discussed here: https://bugs.llvm.org/show_bug.cgi?id=35479.

Original patch author: @hermord (Dmytro Shynkevych)!

Notes:
- In principle, it's possible to also handle the `X % C1 == C2` case, as discussed on bugzilla.
  This seems to require an extra branch on overflow, so I refrained from implementing this for now.
- An explicit check for when the `REM` can be reduced to just its LHS is included:
  the `X % C` == 0 optimization breaks `test1` in `test/CodeGen/X86/jump_sign.ll` otherwise.
  I hadn't managed to find a better way to not generate worse output in this case.
- The `test/CodeGen/X86/jump_sign.ll` regresses, and is being fixed by a followup patch D63390.

Reviewers: RKSimon, craig.topper, spatel, hermord, xbolva00

Reviewed By: RKSimon, xbolva00

Subscribers: xbolva00, javed.absar, llvm-commits, hermord

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D63391

llvm-svn: 364563