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RE: [avr-libc-dev] [bug #28881] nop() macro for NOP instruction


From: Weddington, Eric
Subject: RE: [avr-libc-dev] [bug #28881] nop() macro for NOP instruction
Date: Fri, 12 Feb 2010 23:49:08 -0700

 

> -----Original Message-----
> From: 
> address@hidden 
> [mailto:address@hidden
> org] On Behalf Of Joerg Wunsch
> Sent: Friday, February 12, 2010 5:35 PM
> To: Soren Jorvang; Joerg Wunsch; address@hidden
> Subject: [avr-libc-dev] [bug #28881] nop() macro for NOP instruction
> 
> 
> Follow-up Comment #1, bug #28881 (project avr-libc):
> 
> You guessed it: there's no real place for the nop() macro
> to go into.  That's the main reason it's not yet there.
> 

I agree that there is not a convenient place to put such a macro. But I would 
also argue now that we do not need to have such a macro in avr-libc. The only 
use for the NOP instruction is for some sort of delay, typically by a specific 
number of cycles. This has been available via patches to GCC for a while now. 
These patches add intrinsic functions to the AVR port of GCC and one of those 
intrinsic functions allows the user to delay a specified number of cycles. GCC 
will then generate inline code to do this which takes advantage of NOP and 
other instructions to implement this. These patches are included in the WinAVR 
release, and should be available in other distributions, though I haven't 
checked on other platforms.




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