points-to graph simplification (#16605)
Summary:
This PR reworks the mutability API to be simpler (updates passes to use "mayAlias" calls) and improves the caching logic.
The difference is that we now directly express the idea of a "memory location." Leaves in the alias trackers points-to graph are considered unique memory locations, and mayAlias questions can be boiled down whether two values share a leaf.
To speed up queries, some basic path compression has been added.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/16605
Differential Revision: D13952738
Pulled By: suo
fbshipit-source-id: cfc7fb2b23369f1dc425d1d8ca2c753c193d95dd
