How to jump to labels which are defined in C code

[Altera_Forum]

Hi, 

 In order to speed up system, I write a routine in ASM instructions. Then in asm code, I intend to jump to a label named LOOP which is defined in C code, but I failed. The following error occur:  void Fast_Copy_In_ASM(alt_u32* pSource, alt_u32* pDest, alt_u32 length) { LOOP: asm("ldwio r7,0(r4)"); asm("stwio r7,0(r5)"); asm("addi r5,r5,4");//increase read_data to point to next byte asm("addi r4,r4,4");//increase read_data to point to next byte asm("addi r6,r6,-4");//decrease read_length asm("bne r6,zero,LOOP ");//CWG2  }  error:undefined reference to ‘LOOP’  (1)How to jump to labels which are defined in C code from asm instruction?  (2)Also, pls kindly tell me does there exist any document related to C and ASM mixture coding?  Thanks any help! David http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/tongue.gif

[Altera_Forum]

That is basically inline GCC assembly... that follow the rules of GCC ... you can find many information on the web just searching for "inline gcc assembler" :-) 

 bye,  Paolo

[Altera_Forum]

> error:undefined reference to ‘LOOP’ 

 Put the label inline as well: <div class='quotetop'>QUOTE </div>  --- Quote Start ---  asm volatile (                         "LOOP:  ldwio r7,0(r4)"      "        stwio r7,0(r5)"      "        addi r5,r5,4"           "        addi r4,r4,4"           "        addi r6,r6,-4"       "        bne r6,zero,LOOP " \  );[/b]  --- Quote End ---    Regards, --Scott

[Altera_Forum]

smart idea http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/smile.gif  

 Thanks very much!

[Altera_Forum]

Hi Scott: 

I have tried your code, no compiling error occurred,but something was wrong.  The following code work fine. asm("Fast_Copy_In_ASM_Loop: ldwio r7,0(r4)"); asm("stwio r7,0(r5)"); asm("addi r5,r5,4");//increase read_data to point to next byte asm("addi r4,r4,4");//increase read_data to point to next byte asm("addi r6,r6,-4");//decrease read_length asm("bne r6,zero,Fast_Copy_In_ASM_Loop");//CWG2  But the code you showed me were all skipped when I step into it. asm volatile (   "LOOP: ldwio r7,0(r4)"   " stwio r7,0(r5)"   " addi r5,r5,4"   " addi r4,r4,4"   " addi r6,r6,-4"   " bne r6,zero,LOOP " \  );  WHY?  best regards, David

[Altera_Forum]

> But the code you showed me were all skipped when I step into it. 

... > WHY?  You might be stepping through each statement rather than each instruction. Each "asm" is treated as a statement..  Regards, --Scott

[Altera_Forum]

Hi Scott: 

  But I can&#39;t find the corresponding code in Disassembly window.  So it might be optimized, am I right?  But my optimization level is -O0.  Can you help me to try the code?  SOURCE CODE void Fast_Copy_In_ASM(alt_u32* pSource, alt_u32* pDest, alt_u32 length) { asm volatile (   "Fast_Copy_In_ASM_Loop1: ldwio r7,0(r4)"   " stwio r7,0(r5)"   " addi r5,r5,4"   " addi r4,r4,4"   " addi r6,r6,-4"   " bne r6,zero,Fast_Copy_In_ASM_Loop1 " \  );  //asm("Fast_Copy_In_ASM_Loop: ldwio r7,0(r4)"); //asm("stwio r7,0(r5)"); //asm("addi r5,r5,4");//increase read_data to point to next byte //asm("addi r4,r4,4");//increase read_data to point to next byte //asm("addi r6,r6,-4");//decrease read_length //asm("bne r6,zero,Fast_Copy_In_ASM_Loop");//CWG2  }  Disassembly code <span style="color:red"><span style="color:blue">void Fast_Copy_In_ASM(alt_u32* pSource, alt_u32* pDest, alt_u32 length) {  10053f4: defffc04 addi sp,sp,-16  10053f8: df000315 stw fp,12(sp)  10053fc: d839883a mov fp,sp  1005400: e1000015 stw r4,0(fp)  1005404: e1400115 stw r5,4(fp)  1005408: e1800215 stw r6,8(fp)  0100540c <Fast_Copy_In_ASM_Loop1>: asm volatile (   100540c: 29c00037 ldwio r7,0(r5)  "Fast_Copy_In_ASM_Loop1: ldwio r7,0(r4)"   " stwio r7,0(r5)"   " addi r5,r5,4"   " addi r4,r4,4"   " addi r6,r6,-4"   " bne r6,zero,Fast_Copy_In_ASM_Loop1 " \  );  //asm("Fast_Copy_In_ASM_Loop: ldwio r7,0(r4)"); //asm("stwio r7,0(r5)"); //asm("addi r5,r5,4");//increase read_data to point to next byte //asm("addi r4,r4,4");//increase read_data to point to next byte //asm("addi r6,r6,-4");//decrease read_length //asm("bne r6,zero,Fast_Copy_In_ASM_Loop");//CWG2  }  1005410: df000317 ldw fp,12(sp)  1005414: dec00404 addi sp,sp,16  1005418: f800283a ret</span></span> Thanks a lot! David

[Altera_Forum]

Duh ... sorry : 

 <div class='quotetop'>QUOTE </div>  --- Quote Start ---  asm volatile (       "0:    ldwio r7,0(r4)  \n"      "          stwio r7,0(r5)  \n"      "          addi r5,r5,4  \n"       "          addi r4,r4,4  \n"       "          addi r6,r6,-4    \n"       "          bne r6,zero,0b \n"  );[/b]  --- Quote End ---    Regards, --Scott

[Altera_Forum]

Hi, Scott: 

  No sorry! http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/happy.gif   Thanks very much!  Wish you a best christmas, David

[Altera_Forum]

Hi, Scott: 

  No sorry! http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/happy.gif   Thanks very much!  Wish you a best christmas, David