Revert r153521 as it's causing large regressions on the nightly testers.

Revert r153521 as it's causing large regressions on the nightly testers.
Original commit message for r153521 (aka r153423):
Use the new range metadata in computeMaskedBits and add a new optimization to
instruction simplify that lets us remove an and when loding a boolean value.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153587 91177308-0d34-0410-b5e6-96231b3b80d8