linux-kernel - Re: [PATCH v2 4/6] crypto: lib/sha256 - Unroll SHA256 loop 8 times intead of 64

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Message-ID: <20201023031236.GA135789@rani.riverdale.lan>
Date:   Thu, 22 Oct 2020 23:12:36 -0400
From:   Arvind Sankar <nivedita@...m.mit.edu>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     Arvind Sankar <nivedita@...m.mit.edu>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        David Laight <David.Laight@...lab.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/6] crypto: lib/sha256 - Unroll SHA256 loop 8 times
 intead of 64

On Wed, Oct 21, 2020 at 10:02:19PM -0700, Eric Biggers wrote:
> On Tue, Oct 20, 2020 at 04:39:55PM -0400, Arvind Sankar wrote:
> > This reduces code size substantially (on x86_64 with gcc-10 the size of
> > sha256_update() goes from 7593 bytes to 1952 bytes including the new
> > SHA256_K array), and on x86 is slightly faster than the full unroll
> > (tesed on Broadwell Xeon).
> 
> tesed => tested
> 
> > 
> > Signed-off-by: Arvind Sankar <nivedita@...m.mit.edu>
> > ---
> >  lib/crypto/sha256.c | 166 ++++++++------------------------------------
> >  1 file changed, 30 insertions(+), 136 deletions(-)
> > 
> > diff --git a/lib/crypto/sha256.c b/lib/crypto/sha256.c
> > index c6bfeacc5b81..5efd390706c6 100644
> > --- a/lib/crypto/sha256.c
> > +++ b/lib/crypto/sha256.c
> > @@ -18,6 +18,17 @@
> >  #include <crypto/sha.h>
> >  #include <asm/unaligned.h>
> >  
> > +static const u32 SHA256_K[] = {
> > +	0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
> > +	0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
> > +	0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
> > +	0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
> > +	0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
> > +	0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
> > +	0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
> > +	0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2,
> > +};
> 
> Limit this to 80 columns?

I was aiming for 8 columns per line to match all the other groupings by
eight. It does slightly exceed 100 columns but can this be an exception,
or should I maybe make it 4 columns per line?

> 
> Otherwise this looks good.
> 
> - Eric