Re: [avr-gcc-list] Peculiar code size problem

[David A. Lyons]

The smaller size might be making the compiler decide to inline the function at 
some call sites where it didn't before.  You could experiment with 
"-fno-inline-small-functions" (compiler option) and/or 
"__attribute__((noinline))" on your function declaration:

        void pulse_en (void) __attribute__((noinline));

        void pulse_en (void)
        {
                ...
        }

Cheers,

--Dave

On Mar 17, 2012, at 9:17 PM, Parthasaradhi Nayani wrote:

> 
> Hi all,
> I am working on an ATMEGA8. Since my code was getting close to 8K, I thought 
> I would tweak the code. I have a function listed below
> 
> void pulse_en (void)
> {
>   set_EN; // Set EN
>   _delay_loop_1 (255);
>   clr_EN; // clear EN 
>  _delay_loop_1 (255);
> }
> Since the delay after the "clr" instruction had no meaning, I commented the 
> line and compiled the code hoping I would save a couple of bytes. But to my 
> surprise the code size increased to 7172 bytes compared to 7148 bytes with 
> the function call in place. I looked at the list file and found that the 
> function gets shifted to a different location with and without the function 
> call. Here are the list file snippets
> 
> With the call in place:
> 
> 351               
> 
>       
> pulse_en:
>  352                  .LFB23:
>  353                  .LM47:
>  354                  /* prologue: function */
>  355                  /* frame size = 0 */
>  356                  .LM48:
>  357 0128 C29A                sbi 56-32,2
>  358                  .LBB80:
>  359                  .LBB81:
>  360                  .LM49:
>  361 012a 8FEF                ldi r24,lo8(-1)
>  362 012c 982F                mov r25,r24
>  363                  .LVL17:
>  364                  /* #APP */
>  365                   ;  83 
> "c:/winavr-20100110/lib/gcc/../../avr/include/util/delay_basic.h" 1
>  366 012e 9A95                1: dec r25
>  367 0130 01F4                brne 1b
>  368                   ;  0 "" 2
>  369                  /* #NOAPP */
>  370                  .LBE81:
>  371                  .LBE80:
>  372                  .LM50:
>  373 0132 C298                cbi 56-32,2
>  374                  .LBB82:
>  375                  .LBB83:
>  376                  .LM51:
>  377                  /* #APP */
>  378                   ;  83 
> "c:/winavr-20100110/lib/gcc/../../avr/include/util/delay_basic.h" 1
>  379 0134 8A95                1: dec r24
>  380 0136 01F4                brne 1b
>  381                   ;  0 "" 2
>  382                  .LVL18:
>  383                  /* epilogue start */
>  384                  /* #NOAPP */
>  385                  .LBE83:
>  386                  .LBE82:
>  387                  .LM52:
>  388 0138 0895                ret
> 
> Without the call:
> 621                   .LFE21:
>  623                  .global pulse_en
>  625                  pulse_en:
>  626                  .LFB23:
>  627                  .LM87:
>  628                  /* prologue: function */
>  629                  /* frame size = 0 */
>  630                  .LM88:
>  631 01c2 C29A                sbi 56-32,2
>  632                  .LBB146:
>  633                  .LBB147:
>  634                  .LM89:
>  635 01c4 8FEF                ldi r24,lo8(-1)
>  636                  .LVL36:
>  637                  /* #APP */
>  638                   ;  83 
> "c:/winavr-20100110/lib/gcc/../../avr/include/util/delay_basic.h" 1
>  639 01c6 8A95                1: dec r24
>  640 01c8 01F4                brne 1b
>  641                   ;  0 "" 2
>  642                  /* #NOAPP */
>  643                  .LBE147:
>  644               
> 
>       
> .LBE146:
>  645                  .LM90:
>  646 01ca C298                cbi 56-32,2
>  647                  /* epilogue start */
>  648                  .LM91:
>  649 01cc 0895                ret
> 
> 
> Will some one please let me know why this is happening? If such is the case, 
> perhaps extra code is being generated for other function too. 
> I am using: avr-gcc (WinAVR 20100110) 4.3.3
>  
> Thank you for your time.
> 
> Regards,
> Nayani
> 
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