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Mail Archives: djgpp/2002/04/03/06:30:28

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From: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: help with inline AT&T assembly
Date: Wed, 03 Apr 2002 14:11:30 +0300
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Sterten wrote:
> I'd like to view C as an assembler with "macros" , but I'd have
> to be able to predict the exact opcode being generated.
> And all assembly commands should be part of the C-language.

In most cases, an optimizing compiler will produce a good code, so you don't
need to force it to generate specific opcodes.

> BTW. can I specify which register to use for a C-variable and
> can I change this during the program ?

I don't think so.  It's not a good idea anyway, since you will be fatally
hurting GCC's optimizer.

> Using 3 register variables already helped a lot. (I usually don't
> use register variables , maybe I'll use more in future)

The compiler will put variables in registers if you use -O2.

> Usually  GCC/djgpp 's code is about 30% slower than e.g.
> code from the Intel compiler.

I think this only happens on a K6, which isn't supported as well as ia32

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