LPCXpresso IDE中的主题 Re: Using MULS instruction in Cortex M0

Using MULS instruction in Cortex M0

lpcware — Thu, 16 Jun 2016 00:43:11 GMT

Content originally posted in LPCWare by mahna on Sat Dec 31 08:43:51 MST 2011
When I use MULS instruction in inline assembly, the compiler flags an error.
When I put ".syntax unified" directive, the error is as follows :
Error: Thumb-2 MUL must not set flags
How to use multiply instruction in inline assembly ?

Re: Using MULS instruction in Cortex M0

lpcware — Thu, 16 Jun 2016 00:43:12 GMT

Content originally posted in LPCWare by fastmapper on Sat Dec 31 10:35:36 MST 2011
I have had no problem using the MULS instruction. Here is a code sequence that I have used successfully for a LPC1227:

.syntax unified
muls r5, r3

We could help you more if you could provide a short code sequence that fails along with the associated build settings (including the target device).

Re: Using MULS instruction in Cortex M0

lpcware — Thu, 16 Jun 2016 00:43:13 GMT

Content originally posted in LPCWare by OA santana on Tue Feb 28 05:49:21 MST 2012
My solution. I know it is not an inline command but it might help you.

/************************* some code ************************* /
/**
* @param r0=a
* @param r1=b
* @param r2=c
* @retval r0
*/
__ASM volatile int16_t somemath (int16_t a,int16_t b,int16_t c) {
[INDENT]muls r0,r1,r0
adds r0, r2,r0
BX lr[/INDENT]
}

int main () {
[INDENT] int16_t tmp;
tmp = somemath (10,3,4);
if (tmp != 34) {
/* error */
} else {
/*expected value. */
}[/INDENT]
return(0);
}

/************************* end code ************************* /
Information that might be of your interest :
Procedure Call Standard for the ARM® Architecture
(Document number: ARM IHI 0042D, current through ABI release 2.08)
Hope that helped you.