Optimizing MCJIT module state tracking

Patch co-developed with Yaron Keren.




git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193291 91177308-0d34-0410-b5e6-96231b3b80d8
Clarify comments in genLoopLimit.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193292 91177308-0d34-0410-b5e6-96231b3b80d8