CVS commit: src/common/lib/libc/arch/aarch64/atomic

["Nick Hudson" <skrll%netbsd.org@localhost>]

Module Name:    src
Committed By:   skrll
Date:           Wed Aug 12 12:59:57 UTC 2020

Modified Files:
        src/common/lib/libc/arch/aarch64/atomic: atomic_cas_16.S
            atomic_cas_32.S atomic_cas_64.S atomic_cas_8.S atomic_dec_32.S
            atomic_dec_64.S atomic_inc_32.S atomic_inc_64.S atomic_nand_16.S
            atomic_nand_32.S atomic_nand_64.S atomic_nand_8.S atomic_swap_16.S
            atomic_swap_32.S atomic_swap_64.S atomic_swap_8.S

Log Message:
Part I of ad@'s performance improvements for aarch64

- Remove memory barriers from the atomic ops.  I don't understand why those
  are there.  Is it some architectural thing, or for a CPU bug, or just
  over-caution maybe?  They're not needed for correctness.

- Have unlikely conditional branches go forwards to help the static branch
  predictor.


To generate a diff of this commit:
cvs rdiff -u -r1.1 -r1.2 \
    src/common/lib/libc/arch/aarch64/atomic/atomic_cas_16.S \
    src/common/lib/libc/arch/aarch64/atomic/atomic_cas_32.S \
    src/common/lib/libc/arch/aarch64/atomic/atomic_cas_8.S \
    src/common/lib/libc/arch/aarch64/atomic/atomic_dec_32.S \
    src/common/lib/libc/arch/aarch64/atomic/atomic_dec_64.S \
    src/common/lib/libc/arch/aarch64/atomic/atomic_inc_32.S \
    src/common/lib/libc/arch/aarch64/atomic/atomic_inc_64.S \
    src/common/lib/libc/arch/aarch64/atomic/atomic_nand_16.S \
    src/common/lib/libc/arch/aarch64/atomic/atomic_nand_32.S \
    src/common/lib/libc/arch/aarch64/atomic/atomic_nand_64.S \
    src/common/lib/libc/arch/aarch64/atomic/atomic_nand_8.S \
    src/common/lib/libc/arch/aarch64/atomic/atomic_swap_16.S \
    src/common/lib/libc/arch/aarch64/atomic/atomic_swap_32.S \
    src/common/lib/libc/arch/aarch64/atomic/atomic_swap_64.S \
    src/common/lib/libc/arch/aarch64/atomic/atomic_swap_8.S
cvs rdiff -u -r1.3 -r1.4 \
    src/common/lib/libc/arch/aarch64/atomic/atomic_cas_64.S

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.