There is a lengthy, detailed RFC thread on llvm-dev which discusses the
high level issues. High level discussion is probably best there.
This patch is just an initial step. It isn't really ready for prime time
and is only exposed via debugging flags. It has two major limitations
- It only supports x86-64, and only certain ABIs. Many assumptions are currently hard-coded and need to be factored out of the code here.
- It doesn't include any options for more fine-grained control, either of which control flow edges are significant or which loads are important to be hardened.
However, this is enough for people to begin using. I have had numerous
requests from people to be able to experiment with this patch to
understand the trade-offs it presents and how to use it. We would also
like to encourage work to similar effect in other toolchains.
The ARM folks are actively developing a system based on this for
AArch64. We hope to merge this with their efforts when both are far
enough along. But we also don't want to block making this available on