This reverts commit r285191.
LICM appears to rely on the Alias Set Tracker hitting lifetime markers to prevent
code from being moved outside of the original scope.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@285227 91177308-0d34-0410-b5e6-96231b3b80d8
Repeated inserts into AliasSetTracker have quadratic behavior - inserting a
pointer into AST is linear, since it requires walking over all "may" alias
sets and running an alias check vs. every pointer in the set.
We can avoid this by tracking the total number of pointers in "may" sets,
and when that number exceeds a threshold, declare the tracker "saturated".
This lumps all pointers into a single "may" set that aliases every other
pointer.
(This is a stop-gap solution until we migrate to MemorySSA)
This fixes PR28832.
Differential Revision: https://reviews.llvm.org/D23432
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@279274 91177308-0d34-0410-b5e6-96231b3b80d8
