[all-commits] [llvm/llvm-project] 6b1cf0: [BOLT] Add support for Linux kernel static keys ju...

[Maksim Panchenko via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 6b1cf0040059c407264d2609403c4fc090673167
      https://github.com/llvm/llvm-project/commit/6b1cf0040059c407264d2609403c4fc090673167
  Author: Maksim Panchenko <maks at fb.com>
  Date:   2024-03-21 (Thu, 21 Mar 2024)

  Changed paths:
    M bolt/include/bolt/Core/MCPlus.h
    M bolt/include/bolt/Core/MCPlusBuilder.h
    M bolt/lib/Core/BinaryContext.cpp
    M bolt/lib/Core/BinaryFunction.cpp
    M bolt/lib/Core/MCPlusBuilder.cpp
    M bolt/lib/Passes/BinaryPasses.cpp
    M bolt/lib/Rewrite/LinuxKernelRewriter.cpp
    M bolt/lib/Target/X86/X86MCPlusBuilder.cpp
    A bolt/test/X86/linux-static-keys.s

  Log Message:
  -----------
  [BOLT] Add support for Linux kernel static keys jump table (#86090)

Runtime code modification used by static keys is the most ubiquitous
self-modifying feature of the Linux kernel. The idea is to to eliminate
the condition check and associated conditional jump on a hot path if
that condition (based on a boolean value of a static key) does not
change often. Whenever they condition changes, the kernel runtime
modifies all code paths associated with that key flipping the code
between nop and (unconditional) jump.



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