[all-commits] [llvm/llvm-project] c9a45d: [ARM][KCFI] Fix bundle sizes to reflect worst-case...

[Kees Cook via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: c9a45d3fd777997f669ff6af9c1f27e60a0fa23f
      https://github.com/llvm/llvm-project/commit/c9a45d3fd777997f669ff6af9c1f27e60a0fa23f
  Author: Kees Cook <kees at kernel.org>
  Date:   2025-10-24 (Fri, 24 Oct 2025)

  Changed paths:
    M llvm/lib/Target/ARM/ARMInstrInfo.td

  Log Message:
  -----------
  [ARM][KCFI] Fix bundle sizes to reflect worst-case expansion (#164917)

The KCFI_CHECK pseudo-instruction size for ARM got miscalculated. These
should represent worst-case expansion to ensure correct branch range
calculations and code layout.

Update the Size field for each ARM sub-architecture:

- ARM: 28 → 40 bytes (10 instructions @ 4 bytes when r3 spill needed)
- Thumb2: 32 → 34 bytes (mixed 16/32-bit instructions with r3 spill)
- Thumb1: 50 → 38 bytes (19 instructions @ 2 bytes with r2+r3 spills)

The ARM and Thumb2 sizes were underestimating the case where the target
register is r12, requiring r3 to be used as scratch and
spilled/restored. The Thumb1 size was overestimated and has been
corrected to the actual worst-case of 19 instructions.



To unsubscribe from these emails, change your notification settings at https://github.com/llvm/llvm-project/settings/notifications