Mario Palomo wrote:
m...@horizon.com wrote:
2) Mark it as inline. E.g. in a header file, include
static inline uint16_t __attribute__((const))
convert_endian(uint16_t dt)
{
asm("swpb %0" : "+g" (dt));
return dt;
}
Since it's only one instruction anyway, that will let mspgcc just
drop that one instruction in wherever it's needed.
(Unfortunately, while it does a good job with register variables,
I haven't managed to convince it to generate "swpb @r15+" even when
spoon-fed code that should generate it. Oh, well.)
This does not work if I use this code:
------------------------------------------------------------------------------
/*
endian.c
*/
#include <stdint.h>
static inline uint16_t endian16(uint16_t v)
{
asm("swpb %0" : "+g" (v));
return v;
}
volatile uint16_t value;
int main()
{
value = 0x1122;
endian16(value);
//At this point: value = 0x1122 !!!!
return (int)value;
}//main
------------------------------------------------------------------------------
And I compile using:
msp430-gcc -g3 -mmcu=msp430x149 -o endian.msp endian.c -Wall -O2
The function 'endian16' (with or without __attribute__((const))) compile to
nothing!! Maybe a problem of mspgcc with inline assembler in static inline
functions? I work with msp430-gcc 3.2.3 compiled from CVS (2006-04-10).
If I use a macro to inline the assembler, it works fine (and very optimized):
------------------------------------------------------------------------------
/*
endian.c
*/
#include <stdint.h>
#define endian16(v) asm("swpb %0" : "+g" (v))
volatile uint16_t value;
int main()
{
value = 0x1122;
endian16(value);
//At this point: value = 0x2211
return (int)value;
}//main
------------------------------------------------------------------------------
Any comments? Maybe a bug? Greetings,
Mario Palomo
Mario
Try
<snip>
int main()
{
value = 0x1122;
value = endian16(value);
...
-Bill Knight
R O SoftWare
