linux-kernel - Re: [patch] crypto: sha256-mb - cleanup a || vs

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Message-ID: <1467319339.22178.256.camel@linux.intel.com>
Date:	Thu, 30 Jun 2016 13:42:19 -0700
From:	Tim Chen <tim.c.chen@...ux.intel.com>
To:	"H. Peter Anvin" <hpa@...or.com>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
	Megha Dey <megha.dey@...el.com>,
	"Wang, Rui Y" <rui.y.wang@...el.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Xiaodong Liu <xiaodong.liu@...el.com>,
	linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [patch] crypto: sha256-mb - cleanup a || vs | typo

On Wed, 2016-06-29 at 10:05 -0700, H. Peter Anvin wrote:
> On 06/29/16 07:42, Dan Carpenter wrote:
> > 
> > > 
> > > > 
> > > > and | behave basically the same here but || is intended.  It causes a
> > static checker warning to mix up bitwise and logical operations.
> > 
> > Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> > 
> > diff --git a/arch/x86/crypto/sha256-mb/sha256_mb.c b/arch/x86/crypto/sha256-mb/sha256_mb.c
> > index c9d5dcc..4ec895a 100644
> > --- a/arch/x86/crypto/sha256-mb/sha256_mb.c
> > +++ b/arch/x86/crypto/sha256-mb/sha256_mb.c
> > @@ -299,7 +299,7 @@ static struct sha256_hash_ctx *sha256_ctx_mgr_submit(struct sha256_ctx_mgr *mgr,
> >  	 * Or if the user's buffer contains less than a whole block,
> >  	 * append as much as possible to the extra block.
> >  	 */
> > -	if ((ctx->partial_block_buffer_length) | (len < SHA256_BLOCK_SIZE)) {
> > +	if ((ctx->partial_block_buffer_length) || (len < SHA256_BLOCK_SIZE)) {
> >  		/* Compute how many bytes to copy from user buffer into
> >  		 * extra block
> >  		 */
> > 
> As far as I know the | was an intentional optimization, so you may way
> to look at the generated code.
> 
> 	-hpa
> 

Yes, this is an intentional optimization.  Is there any scenario where things may
break with the compiler?

Tim