Date: Mon, 07 Jan 2002 14:35:00 -0600 From: Stephen Montgomery-Smith <stephen@math.missouri.edu> To: John Baldwin <jhb@FreeBSD.org> Cc: "Matthew D. Fuller" <fullermd@over-yonder.net>, freebsd-hackers@FreeBSD.org Subject: Re: Tell gcc I have a i686 Message-ID: <3C3A0674.5BD4A62C@math.missouri.edu> References: <XFMail.020107115534.jhb@FreeBSD.org>
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John Baldwin wrote:
>
> On 07-Jan-02 Stephen Montgomery-Smith wrote:
> > John Baldwin wrote:
> >>
> >> > You know, I have no idea. It is someone elses code. These are the
> >> > instructions. Can anyone tell me?
> >> >
> >> > "movl 32(%0),%1\n"
> >> > "adcl %1,32(%0)\n"
> >> >
> >> > Also, from this discussion, what I have decided to do is provide it as
> >> > an option for the user to add by editing the Makefile - not to do it
> >> > automatically.
> >>
> >> These instructions are 386 instructions. What we need to see are the
> >> contraints (the stuff after the actual instructions with colons in them) to
> >> see
> >> if it is somehow using Pentium Pro+ specific registers. And actually, just
> >> for
> >> the record, a PPro is a 686. :)
> >>
> >
> > OK, this is it in context:
> >
> > register Word32 *_x = x;
> > register int _a = 0;
> >
> > asm("xorl %1,%1\n" /* clear C */
> > "movl 124(%0),%1\n"
> > "adcl %1,124(%0)\n"
> > : : "r" (_x), "r" (_a)
> > );
>
> Looks like rather silly code to double the value at x + 124. I say silly casue
> it clears carry and then does a addcl. However, since CF is zero, this is the
> same as doing an addl. Since it is just doubling the value, a shl would make
> more sense (and only be 1 instruction.)
>
More likely I am butchering the code by trying to only give you part of
it. The whole code is designed to take N 32 bit words and do a left
shift on it:
register Word32 *_x = x;
register int _a = 0;
asm("xorl %1,%1\n" /* clear C */
"movl (%0),%1\n"
"adcl %1,(%0)\n"
#if (N >= 2)
"movl 4(%0),%1\n"
"adcl %1,4(%0)\n"
#endif
#if (N >= 3)
"movl 8(%0),%1\n"
"adcl %1,8(%0)\n"
#endif
#if (N >= 4)
"movl 12(%0),%1\n"
"adcl %1,12(%0)\n"
#endif
#if (N >= 5)
"movl 16(%0),%1\n"
"adcl %1,16(%0)\n"
#endif
#if (N >= 6)
"movl 20(%0),%1\n"
"adcl %1,20(%0)\n"
#endif
#if (N >= 7)
"movl 24(%0),%1\n"
"adcl %1,24(%0)\n"
#endif
#if (N >= 8)
"movl 28(%0),%1\n"
"adcl %1,28(%0)\n"
#endif
#if (N >= 9)
"movl 32(%0),%1\n"
"adcl %1,32(%0)\n"
#endif
#if (N >= 10)
"movl 36(%0),%1\n"
"adcl %1,36(%0)\n"
#endif
#if (N >= 11)
"movl 40(%0),%1\n"
"adcl %1,40(%0)\n"
#endif
#if (N >= 12)
"movl 44(%0),%1\n"
"adcl %1,44(%0)\n"
#endif
#if (N >= 13)
"movl 48(%0),%1\n"
"adcl %1,48(%0)\n"
#endif
#if (N >= 14)
"movl 52(%0),%1\n"
"adcl %1,52(%0)\n"
#endif
#if (N >= 15)
"movl 56(%0),%1\n"
"adcl %1,56(%0)\n"
#endif
#if (N >= 16)
"movl 60(%0),%1\n"
"adcl %1,60(%0)\n"
#endif
#if (N >= 17)
"movl 64(%0),%1\n"
"adcl %1,64(%0)\n"
#endif
#if (N >= 18)
"movl 68(%0),%1\n"
"adcl %1,68(%0)\n"
#endif
#if (N >= 19)
"movl 72(%0),%1\n"
"adcl %1,72(%0)\n"
#endif
#if (N >= 20)
"movl 76(%0),%1\n"
"adcl %1,76(%0)\n"
#endif
#if (N >= 21)
"movl 80(%0),%1\n"
"adcl %1,80(%0)\n"
#endif
#if (N >= 22)
"movl 84(%0),%1\n"
"adcl %1,84(%0)\n"
#endif
#if (N >= 23)
"movl 88(%0),%1\n"
"adcl %1,88(%0)\n"
#endif
#if (N >= 24)
"movl 92(%0),%1\n"
"adcl %1,92(%0)\n"
#endif
#if (N >= 25)
"movl 96(%0),%1\n"
"adcl %1,96(%0)\n"
#endif
#if (N >= 26)
"movl 100(%0),%1\n"
"adcl %1,100(%0)\n"
#endif
#if (N >= 27)
"movl 104(%0),%1\n"
"adcl %1,104(%0)\n"
#endif
#if (N >= 28)
"movl 108(%0),%1\n"
"adcl %1,108(%0)\n"
#endif
#if (N >= 29)
"movl 112(%0),%1\n"
"adcl %1,112(%0)\n"
#endif
#if (N >= 30)
"movl 116(%0),%1\n"
"adcl %1,116(%0)\n"
#endif
#if (N >= 31)
"movl 120(%0),%1\n"
"adcl %1,120(%0)\n"
#endif
#if (N >= 32)
"movl 124(%0),%1\n"
"adcl %1,124(%0)\n"
#endif
: : "r" (_x), "r" (_a)
);
--
Stephen Montgomery-Smith
stephen@math.missouri.edu
http://www.math.missouri.edu/~stephen
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