I haven't been able to find any references to this error among recent
posts on this list. My apologies, if this turns out to be an old issue ;-)
When any optimization is active (i.e. -Ox for any x>0) msp430-gcc emits
illegal assembly code for calls to memset with length=2 and a pointer
which points to an odd address (i.e. not a word boundary).
The optimizer stage seems to recognize the call to memset and generates
a single word-move instruction even if the address is unknown--or when
it is known to be an odd address. However, according to the MSP430
user's guide (SLAU049E) §1.4.5: "When using word instructions, only even
addresses may be used."
Steps to reproduce (using msp430-gcc version 3.2.3):
Compile the following c code to assembly using some optimization, e.g.
msp430-gcc -O -S test.c
/* test.c start */
#include<string.h>
int array[2];
int main() {
array[0] = 0x5555;
array[1] = 0x5555;
memset(((char*)&array)+1,0,2);
}
/* test.c end */
Inspecting the output, we get (ignoring boilerplate):
mov #llo(21845), &array
mov #llo(21845), &array+2
mov #llo(0), &array+1
The last line is *ILLEGAL* and the contents of array will be 0x00005555
rather than 0x55000055, which is what we expect--and what we will get if
we do not use optimization.
Best regards
/Jacob Andersen
--
Jacob Andersen, Ph.d. student
Department of Computer Science, Aarhus University
Address: Åbogade 34, 8200 Århus N, Denmark
Office: Ada-229
http://ereception.katrinebjerg.net/ereception/browser.jsp?s=jac...@cs
Email: [email protected]
Phone: +45 8942 5747
Mobile: +45 6170 4305
Web: http://www.cs.au.dk/~jacand
