Launch CFI for virtual calls on Linux x86-64.
This is the second incremental step towards the full CFI launch.
In the first step, we enabled LinkTimeOptimization (LTO) for the
official Chrome builds. In this step we add Control Flow Integrity
checks for all virtual calls.
The remaining part is to add bad-cast checks to ensure the forward-edge
Control Flow Integrity works as planned. That remaining part will
require more work on reducing the overhead for size and speed by these
CFI checks, so we don't enable them right away.
The expected Perf impact by this CL:
- Chrome binary size is increased by 5%,
- Some of the benchmarks are slowed down by up to 3.5%.
Note that before making it slower, we made it faster by implementing
virtual const propagation and a number of heuristics for automatic
devirtualization in LLVM which sped up some layout benchmarks by up to 7%
(see https://crbug.com/580389 and https://crbug.com/617283)
If there's a higher (negative) impact, we'll be willing to roll this
feature back, but please allow the Perf bots to work for a day or two
to collect more detailed statistics on the regressions, as it will help
us to identify ways to speed it up (most likely, by inventing new ways
for automatic devirtualization).
BUG=464797
Review-Url: https://codereview.chromium.org/2140373002
Cr-Commit-Position: refs/heads/master@{#405894}
2 files changed
