[PATCH v4 0/3] riscv: optimized mem* functions
Palmer Dabbelt
palmer at dabbelt.com
Thu Oct 7 18:26:44 PDT 2021
On Sun, 19 Sep 2021 12:21:01 PDT (-0700), mcroce at linux.microsoft.com wrote:
> From: Matteo Croce <mcroce at microsoft.com>
>
> Replace the assembly mem{cpy,move,set} with C equivalent.
>
> Try to access RAM with the largest bit width possible, but without
> doing unaligned accesses.
>
> A further improvement could be to use multiple read and writes as the
> assembly version was trying to do.
>
> Tested on a BeagleV Starlight with a SiFive U74 core, where the
> improvement is noticeable.
>
> v3 -> v4:
> - incorporate changes from proposed generic version:
> https://lore.kernel.org/lkml/20210617152754.17960-1-mcroce@linux.microsoft.com/
>
> v2 -> v3:
> - alias mem* to __mem* and not viceversa
> - use __alias instead of a tail call
>
> v1 -> v2:
> - reduce the threshold from 64 to 16 bytes
> - fix KASAN build
> - optimize memset
>
> Matteo Croce (3):
> riscv: optimized memcpy
> riscv: optimized memmove
> riscv: optimized memset
>
> arch/riscv/include/asm/string.h | 18 ++--
> arch/riscv/kernel/Makefile | 1 -
> arch/riscv/kernel/riscv_ksyms.c | 17 ----
> arch/riscv/lib/Makefile | 4 +-
> arch/riscv/lib/memcpy.S | 108 ----------------------
> arch/riscv/lib/memmove.S | 64 -------------
> arch/riscv/lib/memset.S | 113 -----------------------
> arch/riscv/lib/string.c | 154 ++++++++++++++++++++++++++++++++
> 8 files changed, 164 insertions(+), 315 deletions(-)
> delete mode 100644 arch/riscv/kernel/riscv_ksyms.c
> delete mode 100644 arch/riscv/lib/memcpy.S
> delete mode 100644 arch/riscv/lib/memmove.S
> delete mode 100644 arch/riscv/lib/memset.S
> create mode 100644 arch/riscv/lib/string.c
Thanks. These generally look good, but they're failing to build for me.
I'm getting errors along the lines of
arch/riscv/lib/string.c:89:7: error: inlining failed in call to ‘always_inline’ ‘memcpy’: function body can be overwritten at link time
89 | void *memcpy(void *dest, const void *src, size_t count) __weak __alias(__memcpy); | ^~~~~~
arch/riscv/lib/string.c:99:10: note: called from here
99 | return memcpy(dest, src, count);
| ^~~~~~~~~~~~~~~~~~~~~~~~
I'm still a bit behind on email so I'm going to keep going through
patches, but if there's no v5 by the time I get back here then I'll take
a look.
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