gcc 4.6.1 messes up code ?? why

[andy_code <andy_code@xxxxxxxxxx>]

hi,

I have a function I wrote that part of a keypad reading interrupt for an
embbed os we have written for coldfire processors 
in this function the code reads an FPGA that controls the interrupt, it
should only read it once any more and 
it would confuse the FPGA.

here is the original function

void keypad_isr(void)
{
    /*  read a character from the key buffer */
    FPGA_UART_DATA		*ptr;
    FPGA_UART_DATA		kpd;
    int 				g;
    int 				n;
    KEYBUFFER			*kb;
    char				ch;

    kb	= &key_buffer;
    asm(" halt");          /* just for debugging */
    ptr = FPGA_UART;   /* make a pointer to the FPGA register */
    // read upto 8 keys from the keypad
    for( n = 0; n < 8 ; n++ )
    {
        kpd	= *ptr;        /* read from register  (only do this ONCE) */
        g = kpd.fifo_cnt;
        if(g == 0)
            return;
        ch = (char) kpd.rx_data;
        kb->status = ch;
        if( ch != 0 && ch != -1 )
        {
            if ( kb->current_location >= MAX_KEY_BUFFERS_SIZE-1 )
            {
                kb->current_location = MAX_KEY_BUFFERS_SIZE-1;
            }
            kb->key_buff[kb->current_location] = ch;
            kb->current_location++;
        }
    }
}

ok now here is my problem, gcc does not use an address register for the
pointer, and it insists on reading the FPGA directly twice ????
here is generated assembly from gcc.

keypad_isr:
	lea (-12,%sp),%sp
 	movem.l #1036,(%sp)
	move.w -1073741664,%d0         <<<--- should use %a0 surely
	clr.l %d1
	move.w %d0,%d1                    <<< --- theres the read
	moveq #13,%d2
	lsr.l %d2,%d1
	tst.b %d1
	jeq .L3
	moveq #8,%d1
	lea key_buffer+33,%a1
	lea key_buffer,%a0
	lea key_buffer+1,%a2
	jra .L5
.L8:
	move.w -1073741664,%d0       <<< --- look its done it again ?????
	clr.l %d2
	move.w %d0,%d2                  <<< --- ARRRGGGgg its knackered my FPGA
	moveq #13,%d3
	lsr.l %d3,%d2
	tst.b %d2
	jeq .L3
.L5:
	move.b %d0,%d2
	move.b %d0,(%a1)
	move.l %d2,%d0
	addq.l #1,%d0
	and.l #255,%d0
	moveq #1,%d3
	cmp.l %d0,%d3
	jcc .L6
	clr.l %d0
	move.b (%a0),%d0
	move.b #30,%d3
	cmp.l %d0,%d3
	jcc .L7
	move.b #31,(%a0)
.L7:
	move.b (%a0),%d0
	clr.l %d3
	move.b %d0,%d3
	move.b %d2,(%a2,%d3.l)
	addq.l #1,%d0
	move.b %d0,(%a0)
.L6:
	subq.l #1,%d1
 	jne .L8
.L3:
	movem.l (%sp),#1036
	lea (12,%sp),%sp
	rts

ok how do i stop this happening, thats not the code I wrote.
please help, I is tearing my hair out

thank you
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