linux-kernel - Re: [PATCH] trivial: the memset operation on a automatic array variable should be optimized out by data initialization

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Message-ID: <91b13c310706210621n29a2da43lc5caaf14df2bd47b@mail.gmail.com>
Date:	Thu, 21 Jun 2007 21:21:28 +0800
From:	"rae l" <crquan@...il.com>
To:	"Jeremy Fitzhardinge" <jeremy@...p.org>
Cc:	trivial@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] trivial: the memset operation on a automatic array variable should be optimized out by data initialization

On 6/19/07, Jeremy Fitzhardinge <jeremy@...p.org> wrote:
> Denis Cheng wrote:
> > From: Denis Cheng <crquan@...il.com>
> >
> > the explicit memset call could be optimized out by data initialization,
> > thus all the fill working can be done by the compiler implicitly.
> >
>
> How does the generated code change?  Does gcc do something stupid like
> statically allocate a prototype structure full of zeros, and then memcpy
> it in?  Or does it generate a series of explicit assignments for each
> member?  Or does it generate a memset anyway?
>
> Seems to me that this gives gcc the opportunity to be more stupid, and
> the only right answer is what we're doing anyway.
>
>     J
>
Technically speaking, C standard guarantees the data be initialized correctly;
just from the point view of code style, let the compiler selects how
to initialize will be better, this could let the compiler has more
optimization points.

-- 
Denis Cheng
Linux Application Developer
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