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asm: XBANZ within .loop

og
Prodigy 60 points

Hi

I am developing a high-performance assembly routine on the F28027 microcontroller and was wondering how to use branch statements within the .loop directive


	.loop 5
	<code>
	 XBANZ skip, *--
	<code>
skip:
	<code> 
	.endloop

Of course, this produces the assembly error "Symbol skip has already been defined". What is the correct way to achieve this behaviour? 

  • 0
    Genius 5885 points

    Hi og,

    You might try using assembly macro labels (append "?" after the label), though I don't know if they work outside of assembly macros. I can confirm that they work within macros.

     

    Regards, Mitja

  • 0 in reply to Mitja Nemec
    Prodigy 60 points

    Hi Mitja

    Thanks for your suggestion. Unfortunately the ? trick doesn't work outside of a macro. I've worked around the problem by moving the affected part of code into a macro. Although it fixes the problem it makes the code even more difficult to follow. Sounds like the ability to use ? inside a .loop construct would be a useful addition to the asm spec.

    Og

  • 0 in reply to og
    TI__Guru**** 249420 points

    The C28x Assembly Language Tools book http://www-s.ti.com/sc/techlit/spru513 , in section 5.3.4, has an example of auto-generating a label within .loop.  It happens to all occur within a macro.  But I think that is incidental to this example, and not required.

    Thanks and regards,

    -George

     

  • 0 in reply to George Mock
    Prodigy 60 points

    Thanks for this George - this did indeed solve the problem, despite the section in question clearly stating that the forced substitution operator only works within macros.

    To summarise: To achieve the objective described by

    	.loop 5
    	<code>
    	BANZ skip, AR1--
    	<code>
    skip:
    	<code>
    	.endloop

    I used the following:
    	.eval 5, N
    	.loop
    	<code>
    	BANZ skip:N:, AR1--
    	<code>
    skip:N:
    	<code>
    	.eval N+1, N
    	.break N = 5
    	.endloop