ld-2.12.1, PowerPC

ld-2.12.1, PowerPC

[Etienne Lorrain]

  Hello,

----------------------
$ local/bin/xas --version
GNU assembler 2.12.1
Copyright 2002 Free Software Foundation, Inc.
This program is free software; you may redistribute it under the terms of
the GNU General Public License.  This program has absolutely no warranty.
This assembler was configured for a target of `powerpc-eabi'.

Administrator@NDSUK4908 ~
$ local/bin/xas -m603 -al -o a.o
        li      %r0,0
        a_label:
        subi    %r3,%r3,a_label@l
GAS LISTING                     page 1


   1 0000 38000000      li %r0,0
   2                    a_label:
   3 0004 38630000      subi %r3,%r3,a_label@l

Administrator@NDSUK4908 ~
$ local/bin/xld a.o
local/bin/xld: warning: cannot find entry symbol _start; defaulting to
01800074

Administrator@NDSUK4908 ~
$ local/bin/xobjdump -D a.out

a.out:     file format elf32-powerpc

Disassembly of section .text:

01800074 <a_label-0x4>:
 1800074:       38 00 00 00     li      r0,0

01800078 <a_label>:
 1800078:       38 63 00 78     addi    r3,r3,120
Disassembly of section .sdata2:
Disassembly of section .data:
Disassembly of section .sdata:
----------------------

  Everything is right, but why the subi has been changed by xld to addi ?
 It could have been "addi r3,r3,0xFF88", but it is not (-120 = 0xFF88).
 Please say me I did not wake up this morning...

  Thanks,
  Etienne.


___________________________________________________________
Do You Yahoo!? -- Une adresse @yahoo.fr gratuite et en français !
Yahoo! Mail : http://fr.mail.yahoo.com

Re: ld-2.12.1, PowerPC

[Alan Modra]

On Fri, Oct 11, 2002 at 11:50:30AM +0200, Etienne Lorrain wrote:
> $ local/bin/xas -m603 -al -o a.o
>         li      %r0,0
>         a_label:
>         subi    %r3,%r3,a_label@l
[snip]
> Disassembly of section .text:
> 
> 01800074 <a_label-0x4>:
>  1800074:       38 00 00 00     li      r0,0
> 
> 01800078 <a_label>:
>  1800078:       38 63 00 78     addi    r3,r3,120
> ----------------------
> 
>   Everything is right, but why the subi has been changed by xld to addi ?

Well, there isn't a powerpc subi instruction at the machine level.
subi is really a macro, with "subi Rx,Ry,value" equivalent to
"addi Rx,Ry,-value".

>  It could have been "addi r3,r3,0xFF88", but it is not (-120 = 0xFF88).

gas should have rejected your source, as it's not possible in
general to use the negative of a (non-absolute) label.

-- 
Alan Modra
IBM OzLabs - Linux Technology Centre

Re: ld-2.12.1, PowerPC

[Etienne Lorrain]

 --- Alan Modra <amodra@bigpond.net.au> a écrit : 
> On Fri, Oct 11, 2002 at 11:50:30AM +0200, Etienne Lorrain wrote:
> >  It could have been "addi r3,r3,0xFF88", but it is not (-120 = 0xFF88).
> 
> gas should have rejected your source, as it's not possible in
> general to use the negative of a (non-absolute) label.

  An error message in gas would be a good solution.
  Etienne.

___________________________________________________________
Do You Yahoo!? -- Une adresse @yahoo.fr gratuite et en français !
Yahoo! Mail : http://fr.mail.yahoo.com