Fix llvm::ComputeNumSignBits with some operations and llvm.assume

Currently ComputeNumSignBits does early exit while processing some
of the operations (add, sub, mul, and select). This prevents the
function from using AssumptionCacheTracker if passed.

Differential Revision: https://reviews.llvm.org/D49759

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@337936 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed