On Wed, Aug 05, 2020 at 01:17:29PM +0200, Uros Bizjak wrote:
> Current minimum required version of binutils is 2.23,
> which supports CRC32 instruction mnemonic.
> 
> Replace the byte-wise specification of CRC32 with this proper mnemonic.
> The compiler is now able to pass memory operand to the instruction,
> so there is no need for a temporary register anymore.
> 
> Some examples of the improvement:
> 
>  12a: 48 8b 08                mov    (%rax),%rcx
>  12d: f2 48 0f 38 f1 f1       crc32q %rcx,%rsi
>  133: 48 83 c0 08             add    $0x8,%rax
>  137: 48 39 d0                cmp    %rdx,%rax
>  13a: 75 ee                   jne    12a <crc32c_intel_update+0x1a>
> 
> to:
> 
>  125: f2 48 0f 38 f1 06       crc32q (%rsi),%rax
>  12b: 48 83 c6 08             add    $0x8,%rsi
>  12f: 48 39 d6                cmp    %rdx,%rsi
>  132: 75 f1                   jne    125 <crc32c_intel_update+0x15>
> 
> and:
> 
>  146: 0f b6 08                movzbl (%rax),%ecx
>  149: f2 0f 38 f0 f1          crc32b %cl,%esi
>  14e: 48 83 c0 01             add    $0x1,%rax
>  152: 48 39 d0                cmp    %rdx,%rax
>  155: 75 ef                   jne    146 <crc32c_intel_update+0x36>
> 
> to:
> 
>  13b: f2 0f 38 f0 02          crc32b (%rdx),%eax
>  140: 48 83 c2 01             add    $0x1,%rdx
>  144: 48 39 ca                cmp    %rcx,%rdx
>  147: 75 f2                   jne    13b <crc32c_intel_update+0x2b>
> 
> As the compiler has some more freedom w.r.t. register allocation,
> there is also a couple of reg-reg moves removed.
> 
> There are no hidden states for CRC32 insn, so there is no need to mark
> assembly as volatile.
> 
> v2: Introduce CRC32_INST define.
> 
> Signed-off-by: Uros Bizjak <ubiz...@gmail.com>
> CC: Herbert Xu <herb...@gondor.apana.org.au>
> CC: "David S. Miller" <da...@davemloft.net>
> CC: Thomas Gleixner <t...@linutronix.de>
> CC: Ingo Molnar <mi...@redhat.com>
> CC: Borislav Petkov <b...@alien8.de>
> CC: "H. Peter Anvin" <h...@zytor.com>
> ---
>  arch/x86/crypto/crc32c-intel_glue.c | 18 ++++++------------
>  1 file changed, 6 insertions(+), 12 deletions(-)

Patch applied.  Thanks.
-- 
Email: Herbert Xu <herb...@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

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