[0/5] ARM: findbit assembly updates

Message

Russell King (Oracle) Oct. 28, 2022, 4:47 p.m. UTC

Hi,

This series updates the arm32 assembly versions of the findbit
operations:

- Document ARMv5 code that calculates the bit offset
- Provide an updated ARMv7 implementation using the rbit instruction
- Switch to use macros instead of duplicating mostly identical code
- Switch to using word loads rather than byte loads
- Add unwinder information for backtracing

I've had it sitting around in-use for some time, and no issues have
arisen. Tested also outside the kernel tree in userspace and results
are the same with the previous implementation.

Testing with the find_bit benchmark module shows that these operations
coded in assembly are faster than the generic versions (previously
posted), so I believe they're worth keeping.

 arch/arm/include/asm/assembler.h |   6 +
 arch/arm/lib/findbit.S           | 230 +++++++++++++++------------------------
 2 files changed, 94 insertions(+), 142 deletions(-)