As BillW suggests, what you're missing is the significance of "gcc
doesn't support 20-bit". Using -S as I recommended would show you
that gcc is adding a truncation operator around the immediate in your
asm statement, because it knows no instruction accepts an immediate
larger than 16 bits.
/* #APP */
; 16 "h.c" 1
movx.a #llo(982782),&__DMA0SA
; 0 "" 2
/* #NOAPP */
Presumably, the same thing is happening in the Zolertia variant you
didn't mention that you were using. Take that up with them.
BillW's suggestion is unlikely to work because the assembler does not
(I believe) support shift operations on operands, but give it a try.
The assembler does support 20-bit immediates and appears to properly
process certain extended instructions when fed in through asm
statements, which was the main concern I had. I have no further
suggestions on how you might convince mspgcc to produce acceptable
assembler source when the immediate is not a compile-time constant
that can become part of the output template in the asm statement, as
with:
__asm__ __volatile__ ("movx.a #0xefefe,%0":"=m" (DMA0SA));
Peter
On Thu, Apr 14, 2011 at 10:50 PM, Eric Decker <cire...@gmail.com> wrote:
>
>
> On Thu, Apr 14, 2011 at 4:21 PM, Peter Bigot <big...@acm.org> wrote:
>>
>> And yes, if you did it in assembler, you could use a 20-bit immediate.
>>
>> Peter
>>
>> >> Can the msp430X instruction set even access a 20 bit immediate field?
>
> This is kind of what I was getting at....
>
> From my original post:
>
>
>> Anyone know how to get 20 bit immediate in gcc extended asm?
>>
>> ie.
>>
>> __asm__ __volatile__ ("movx.a %1,%0":"=m" (DMA0SA):"i" (0xefefeUL));
>
> Note the immediate field is 0xefefe (20 bits).
>
>>
>> which unfortunately generates...
>>
>> __asm__ __volatile__ ("movx.a %1,%0":"=m" (DMA0SA):"i" (0xefefeUL));
>> 3b12: 00 18 f2 40 fe fe d2 01 movx.a #65278,&0x001d2;#0x0fefe
>
> looks like the immediate got tweaked from 0xefefe to 0x0fefe.
>
> From what I've figured out from the user's guide, I suspect that this should
> havebits for the immediate. Am I missing anything? Right now it looks to
> me that
> generated 00 18 f2 4e fe fe d2 01. And this is a bug in the gcc asm code
> in mspgcc
> 3.2.3.
>
> Am I missing anything?
>
>
>> Can the msp430X instruction set even access a 20 bit immediate field?
>>
>
>
> --
> Eric B. Decker
> Senior (over 50 :-) Researcher
>
>
>
------------------------------------------------------------------------------
Benefiting from Server Virtualization: Beyond Initial Workload
Consolidation -- Increasing the use of server virtualization is a top
priority.Virtualization can reduce costs, simplify management, and improve
application availability and disaster protection. Learn more about boosting
the value of server virtualization. http://p.sf.net/sfu/vmware-sfdev2dev
_______________________________________________
Mspgcc-users mailing list
Mspgcc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/mspgcc-users
