From: Eric Biggers <ebiggers@xxxxxxxxxx> For handling the 0 <= len < sizeof(unsigned long) bytes left at the end, do a 4-2-1 step-down instead of a byte-at-a-time loop. This allows taking advantage of wider CRC instructions. Note that crc32c-3way.S already uses this same optimization too. crc_kunit shows an improvement of about 25% for len=127. Suggested-by: H. Peter Anvin <hpa@xxxxxxxxx> Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx> --- This applies to https://web.git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux.git/log/?h=crc-next arch/x86/lib/crc32-glue.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/arch/x86/lib/crc32-glue.c b/arch/x86/lib/crc32-glue.c index 4b4721176799a..e3f93b17ac3f1 100644 --- a/arch/x86/lib/crc32-glue.c +++ b/arch/x86/lib/crc32-glue.c @@ -55,11 +55,19 @@ u32 crc32c_arch(u32 crc, const u8 *p, size_t len) for (num_longs = len / sizeof(unsigned long); num_longs != 0; num_longs--, p += sizeof(unsigned long)) asm(CRC32_INST : "+r" (crc) : ASM_INPUT_RM (*(unsigned long *)p)); - for (len %= sizeof(unsigned long); len; len--, p++) + if (sizeof(unsigned long) > 4 && (len & 4)) { + asm("crc32l %1, %0" : "+r" (crc) : ASM_INPUT_RM (*(u32 *)p)); + p += 4; + } + if (len & 2) { + asm("crc32w %1, %0" : "+r" (crc) : ASM_INPUT_RM (*(u16 *)p)); + p += 2; + } + if (len & 1) asm("crc32b %1, %0" : "+r" (crc) : ASM_INPUT_RM (*p)); return crc; } EXPORT_SYMBOL(crc32c_arch); base-commit: 13f3d13d88b5dcba104a204fcbee61c75f8407d0 -- 2.48.1
