From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <ee9e417a0503101405303258f3@mail.gmail.com>
Date: Thu, 10 Mar 2005 17:05:25 -0500
From: Russ Cox <russcox@gmail.com>
To: Fans of the OS Plan 9 from Bell Labs <9fans@cse.psu.edu>
Subject: Re: [9fans] ARM question
In-Reply-To: <Pine.LNX.4.58.0503101453470.13080@enigma.lanl.gov>
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References: <Pine.LNX.4.58.0503101453470.13080@enigma.lanl.gov>
Topicbox-Message-UUID: 22e1701c-ead0-11e9-9d60-3106f5b1d025

perhaps the argument to MOVW.P is the final
(post-increment) value instead of the value used
during the write.


On Thu, 10 Mar 2005 14:55:37 -0700 (MST), Ronald G. Minnich
<rminnich@lanl.gov> wrote:
>
> here's the code in c:
> #include <u.h>
> #include <libc.h>
> y(){
>         unsigned long *x;
>         x = (unsigned long *) 0x4000;
>         *x = (unsigned long) 0x40e;
> }
> main(){
>         unsigned long *x;
>         static unsigned long y[64];
>         int i;
>
>         x = (unsigned long *) 0x4000;
>         *x = (unsigned long) 0x40e;
>         x++;
>         *x = (unsigned long)0x100000 + 0x40e;
>         x++;
>         *x = (unsigned long)0x200000 + 0x40e;
>         x++;
>         *x = (unsigned long)0x300000 + 0x40e;
>         x++;
>         *x = (unsigned long)0x400000 + 0x40e;
>         x++;
>         *x = (unsigned long)0x500000 + 0x40e;
>         x++;
>         *x = (unsigned long)0x600000 + 0x40e;
>         x++;
>         *x = (unsigned long)0x700000 + 0x40e;
>
> }
>
> And the .s
>         TEXT    y+0(SB),0,$4
>         MOVW    $1038,R4
>         MOVW    $16384,R1
>         MOVW    R4,0(R1)
>         RET     ,
>         TEXT    main+0(SB),0,$8
>         MOVW    $1049614,R10
>         MOVW    $2098190,R9
>         MOVW    $3146766,R8
>         MOVW    $4195342,R7
>         MOVW    $5243918,R6
>         MOVW    $6292494,R5
>         MOVW    $7341070,R4
>         MOVW    $16384,R3
>         MOVW    $1038,R2
>         MOVW.P  R2,4(R3)
>         MOVW.P  R10,4(R3)
>         MOVW.P  R9,4(R3)
>         MOVW.P  R8,4(R3)
>         MOVW.P  R7,4(R3)
>         MOVW.P  R6,4(R3)
>         MOVW    R5,0(R3)
>         MOVW    R4,4(R3)
>         RET     ,
>         GLOBL   y$2<>+0(SB),R0,$256
>         END     ,
>
> The code for y() I can understand.
>
> but this:
>
>         MOVW    $16384,R3
>         MOVW    $1038,R2
>         MOVW.P  R2,4(R3)
>
> I don't get. How can R2 get stored to 16384, given the 4(R3)?
>
> Are we pretty much agreed that the MOVW.P is a post-increment mode?
>
> ron
>