Sure you're right.
But I wonder why he got an error while I don't.
I looked at the generated code and the compiler generated a constant containing
the value (PORT1_VECTOR-512), and the branch brances onto the location pointed
to by this constant.
Of course this isn't what was intended, but it produces no error on my system.
The compiler generates an lvalue. And since it is an input an dnot an output
parameter, the 'lvalue' may be constant too.
here's the example:
#define VECTOR_OFFSET (-512)
interrupt (PORT1_VECTOR) __attribute((naked)) PORT1SR (void) {
asm("br %[add]" :: [add] "m" (PORT1_VECTOR + VECTOR_OFFSET));
}
1659 .stabs "j:r(0,4)",64,0,204,11
1660 .stabn 192,0,0,.LBB25-testThread3
1661 .stabn 224,0,0,.LBE25-testThread3
1662 .Lscope8:
1663 .stabs "",36,0,0,.Lscope8-testThread3
1664 .p2align 1,0
1665 .LC17:
1666 0840 5EFE .short -418
1667 .p2align 1,0
1668 .stabs "PORT1SR:F(0,20)",36,0,218,PORT1SR
1669 .global PORT1SR
1670 .global vector_ffde
1671 .type PORT1SR,@function
1672 /***********************
1673 * Interrupt Service Routine `PORT1SR' at 0xffde
1674 ***********************/
1675 vector_ffde:
1676 PORT1SR:
215:ez3.c ****
216:ez3.c ****
217:ez3.c **** #define VECTOR_OFFSET (-512)
218:ez3.c **** interrupt (PORT1_VECTOR) __attribute((naked)) PORT1SR
(void) {
1677 .stabn 68,0,218,.LM198-PORT1SR
1678 .LM198:
1679 /* prologue: naked */
1680 .L__FrameSize_PORT1SR=0x0
219:ez3.c **** asm("br %[add]" :: [add] "m" (PORT1_VECTOR +
VECTOR_OFFSET));
1681 .stabn 68,0,219,.LM199-PORT1SR
1682 .LM199:
1683 /* #APP */
1684 0842 1042 0000 br &.LC17
220:ez3.c **** }
1685 .stabn 68,0,220,.LM200-PORT1SR
1686 .LM200:
1687 /* #NOAPP */
1688
1689 /* epilogue: naked */
1690 .Lfe10:
1691 .size PORT1SR,.Lfe10-PORT1SR
1692 /********* End of function ******/
Of course that's not what was wanted. Using the 'i' constraint instead of the
'm' constraint had had the same result, just without the additional memory
constant:
1681 0840 1042 5EFE br #llo(-418)
With your modification, the compiler generates
1681 0840 1042 5EFE br &-418
which is the intended result.
I still wonder why he got an error message. Maybe PORT1_VECTOR was unknown, in
addition to the wrong addressing mode/parameter type.
JMGross
----- Ursprüngliche Nachricht -----
Von: Peter Bigot
An: GCC for MSP430 - http://mspgcc.sf.net
Gesendet am: 16.Juni.2010 22:02:52
Betreff: Re: [Mspgcc-users] memory input 0 is not directly addressable
The value of PORT1_VECTOR + VECTOR_OFFSET is an integer, which is not the
same as an addressable memory location. In gcc4, the parameter to a memory
reference has to be an lvalue.
Try something like:
asm("br %[add]" :: [add] "m" (*(uint16_t*)(PORT1_VECTOR +
VECTOR_OFFSET)));
Peter
