[all-commits] [llvm/llvm-project] 5a2988: [BOLT] Add writing support for Linux kernel ORC (#...

[Maksim Panchenko via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 5a2988714509d96d72b64e0c64998deb705d3572
      https://github.com/llvm/llvm-project/commit/5a2988714509d96d72b64e0c64998deb705d3572
  Author: Maksim Panchenko <maks at fb.com>
  Date:   2024-02-16 (Fri, 16 Feb 2024)

  Changed paths:
    M bolt/lib/Rewrite/LinuxKernelRewriter.cpp
    M bolt/test/X86/linux-orc.s

  Log Message:
  -----------
  [BOLT] Add writing support for Linux kernel ORC (#80950)

Update ORC information based on the new code layout and emit
corresponding ORC sections for the Linux kernel.

We rewrite ORC sections in place, which puts a limit on the size of new
section contents. Since ORC info changes for the new code layout and the
number of ORC entries can become larger, we free up space in the tables
by removing redundant ORC terminators. As a result, we effectively emit
fewer entries and have to add duplicate terminators at the end to match
the original section sizes. Ideally, we need to update ORC boundaries to
reflect the reduced size and optimize runtime lookup, but we will need
relocations for this, and the benefits will be marginal, if any.



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