The goal of this change is fixing most of compile time slowdown seen after a630ea3003 commit on lencod and sqlite3 benchmarks.
There are 3 improvements included in this patch:
1. In getNumOperands when possible get value directly from SmallNumOps.
2. Inline getLargePtr by moving its definition to header.
3. In TBAAStructTypeNode::getField get all operands once instead taking operands in loop one after one.
Differential Revision: https://reviews.llvm.org/D129468