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[avr-libc-dev] revised:problem with inline assembly


From: varsha
Subject: [avr-libc-dev] revised:problem with inline assembly
Date: Tue, 20 Sep 2005 10:27:34 +0530





hello everyone,
As  mentioned in the pdf avr-libc-user-manual -1.2.3, in the section 7.4.7C 
"names used in Assembler code",
that with WINAVR GCC we can specify use of specific register by using 
syntax...
register unsigned char counter asm("r3");

so that assembler will use register r3 when we do operations with counter 
variable...

but i tried it one program but doesn't work....!!

if i specify say 4 variables in my c program crc0,crc1,crc3and crc4...as
register unsigned char crc0 asm("r11");
register unsigned char crc1 asm("r12");
register unsigned char crc2 asm("r13");
register unsigned char crc3 asm("r14");

crc0=crc1=crc2=crc3=0xff;              //assign some vaue to them...

__asm__ __volatile__      
   (           
    "lsl crc0"     "\n\t"                        //this doesn't work
    "rol crc1"     "\n\t"                        //it gives error as constant 
value required
    "rol crc2"     "\n\t" 
    "rol crc3"
   ); 


__asm__ __volatile__      
   (           
    "lsl crc0"     "\n\t" 
    "rol r12"     "\n\t"                            //this works
    "rol r13"     "\n\t" 
    "rol r14"
   ); 

please reply soon,
thanks and regards,
varsha

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