[all-commits] [llvm/llvm-project] 447d30: [JITLink][MachO][arm64] Mask high bits out of imme...

[lhames via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 447d3017e476e1dd2a5779051f26fa5eb12d9465
      https://github.com/llvm/llvm-project/commit/447d3017e476e1dd2a5779051f26fa5eb12d9465
  Author: Lang Hames <lhames at gmail.com>
  Date:   2021-10-12 (Tue, 12 Oct 2021)

  Changed paths:
    M llvm/lib/ExecutionEngine/JITLink/MachO_arm64.cpp

  Log Message:
  -----------
  [JITLink][MachO][arm64] Mask high bits out of immediate for LDRLiteral19.

Negative deltas for LDRLiteral19 have their high bits set. If these bits aren't
masked out then they will overwrite other instruction bits, leading to a bogus
encoding.

This long-standing relocation bug was exposed by e50aea58d59, "[JITLink][ORC]
Major JITLinkMemoryManager refactor.", which caused memory layouts to be
reordered, which in turn lead to a previously unseen negative delta. (Unseen
because LDRLiteral19s were only created in JITLink passes where they always
pointed at segments that were layed-out-after in the old layout).

No testcase yet: Our existing regression test infrastructure is good at checking
that operand bits are correct, but provides no easy way to test for bad opcode
bits. I'll have a think about the right way to approach this.

https://llvm.org/PR52153