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Date: Sun, 12 Jun 2005 13:50:20 +0200
From: Willy Tarreau <willy@w.ods.org>
To: Mikael Pettersson <mikpe@csd.uu.se>
Cc: marcelo.tosatti@cyclades.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2.4.31 7/9] gcc4: fix const function warnings
Message-ID: <20050612115019.GJ28759@alpha.home.local>
References: <200506121121.j5CBLGd4019750@harpo.it.uu.se>
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Hi Mikael,

Just out of curiosity, I understand why we can have a const on an inline
function to help the compiler optimize the code at compile time in cases
such as below :

> -static inline const unsigned char dehex(char c) {
> +static inline __attribute_const__ unsigned char dehex(char c) {
>  	if ((c>='0')&&(c<='9')) {
>  		return c-'0';
>  	}

But I don't see how it can be useful in asm code like below, since the
compiler cannot evaluate it at compile time :

> -static __inline__ __const__ __u32 ___arch__swab32(__u32 x)
> +static __inline__ __attribute_const__ __u32 ___arch__swab32(__u32 x)
>  {
>  #ifdef CONFIG_X86_BSWAP
>  	__asm__("bswap %0" : "=r" (x) : "0" (x));

Am I missing something, or could we simply remove the __const__ every
time the function only uses asm ?

Regards,
Willy