[PATCH] D84471: [X86] Fix for ballooning compile times due to Load Value Injection (LVI) mitigations

[Scott Constable via Phabricator via llvm-commits]

sconstab created this revision.
sconstab added reviewers: mattdr, craig.topper.
Herald added subscribers: jfb, JDevlieghere, hiraditya.
Herald added a project: LLVM.

Fix for the issue raised in https://github.com/rust-lang/rust/issues/74632.

The current heuristic for inserting `LFENCE`s uses a quadratic-time algorithm. This can apparently cause substantial compilation slowdowns for building Rust projects, where functions > 5000 LoC are apparently common.

The updated heuristic in this patch implements a linear-time algorithm. On a set of benchmarks, the slowdown factor for the generated code was comparable (2.55x geo mean for the quadratic-time heuristic, vs. 2.58x for the linear-time heuristic). Both heuristics offer the same security properties, namely, mitigating LVI.

This patch also includes some formatting fixes.


https://reviews.llvm.org/D84471

Files:
  llvm/lib/Target/X86/X86LoadValueInjectionLoadHardening.cpp

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