From: "Joel_S" <jbs30000 DOT news DOT invalid AT web2news DOT net>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: C/C++ versions of asm opcodes.
Date: Wed, 22 Jan 2003 01:48:55 +0100
Organization: Web2news.com
Message-ID: <12335N735@web2news.com>
References: <12212N341 AT web2news DOT com> <GN9X9.29467$jM5 DOT 76104 AT newsfeeds DOT bigpond DOT com>
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To: djgpp AT delorie DOT com
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Reply-To: djgpp AT delorie DOT com

Thank you.

> ADC and SBB require a carry flag, and since C has no way
> of getting it,
> you'd have to emulate it. If you did that, then maybe a
> very smart compiler
> _might_ catch on and use ADC or SBB.
> As for ROL and ROR, they are simple, and some optimizing
> compilers might
> convert equivalent C code to ROL or ROR.
>
> unsigned long rol (unsigned long src, unsigned long samt){
>     return (src << samt) | (src >> (32 - samt));
> }
>
> unsigned long ror (unsigned long src, unsigned long samt){
>     return (src >> samt) | (src << (32 - samt));
> }
>
> unsigned long add (unsigned long src, unsigned long tgt, int *carry){
>     unsigned long dst;
>     dst = src + tgt;
>     carry = (dst < src);
>     return dst;
> }
>
> unsigned long adc (unsigned long src, unsigned long tgt, int *carry){
>     unsigned long dst;
>     dst = src + tgt + (carry ? 1 : 0);
>     carry = (dst < src);
>     return dst;
> }
>
> unsigned long sub (unsigned long src, unsigned long tgt, int *carry){
>     unsigned long dst;
>     dst = src - tgt;
>     carry = (src < tgt);
>     return dst;
> }
>
> unsigned long sbb (unsigned long src, unsigned long tgt, int *carry){
>     unsigned long dst;
>     dst = src - tgt - carry;
>     carry = (src < (tgt + carry));
>     return dst;
> }
>
> Joel_S <jbs30000 DOT news DOT invalid AT web2news DOT net> wrote in message
> news:12212N341 AT web2news DOT com...
>> Ok, there are some C/C++ functions for asm opcodes, like
>> << and >> for
>> shl and shr (using Intel assembly syntax instead of AT&T).
>> And I know how to translate some opcodes that don't have a C/C++
>> equivalent.  But there are some things in asm that I'm
>> wondering if I
>> could do in C or C++, like
>> ror
>> rol
>> adc
>> sbb
>> if anybody knows how to do these in C, I'd like to know.  Thanks.

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