From: "Tom St Denis" <tomstdenis AT yahoo DOT com>
Newsgroups: comp.os.msdos.djgpp
References: <5BF60CD649EDD411A04600B0D049F53A544465 AT hydmail02 DOT hyd DOT wilco-int DOT com>
Subject: Re: Accessing registers from C
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Date: Mon, 02 Jul 2001 03:33:28 GMT
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"Prashant Ramachandra" <rprash AT wilco-int DOT com> wrote in message
news:5BF60CD649EDD411A04600B0D049F53A544465 AT hydmail02 DOT hyd DOT wilco-int DOT com...
> On Monday, July 02, 2001 2:28 AM, Tom St Denis [SMTP:tomstdenis AT yahoo DOT com]
> wrote:
> |
> | "Jacek K." <xos AT o2 DOT pl> wrote in message news:9hns3d$4rn$1
> | @news.tpi.pl...
> | > Are there some instructions/macros to access CPU registers?
> | > Anything other
> | > than inline assembly, of course.
> |
> | No and you shouldn't.
>
> And why not?
>
> Try this:
>
> void foo ()
> {
> register unsigned long eax __asm__ ("ax");
>
> ...
> }
>
> Everytime you use the variable "eax", you're actually accessing or
modifying
> the eax register itself.

Perhaps, and by doing so you take away chances for GCC to optimize the code.

You might as well not write in C then.

Tom