Re: [avr-gcc-list] gcc prolog incorrect?

[Ben L. Titzer]

It seems as though the code restores the interrupt mask to exactly as 
it was before the call; if the cli were to come first, the I flag would 
be written to 0 and thus would not be restored correctly.

The thing I wonder about is what happens if there is an interrupt 
between 72 and 73....It seems to me that those two instructions should 
be swapped...

On Mar 6, 2005, at 6:12 PM, address@hidden wrote:

> Is it possible that gcc prolog is incorrect?
>
>   69 000a 0FB6              in __tmp_reg__,__SREG__
>   70 000c F894              cli
>   71 000e DEBF              out __SP_H__,r29
>   72 0010 0FBE              out __SREG__,__tmp_reg__
>   73 0012 CDBF              out __SP_L__,r28
>
> This is the code used to adjust the stack pointer for a regular 
> function with interrupts active. Basically it turns of interupts so it 
> can chnage both bytes of SP without a problem.
>
> But saved BEFORE interrupts are disabled. Doesn't that mean that if 
> interrupts were disabled during ISR, a function could re-enabled them 
> when SREG is restored?
>
>
>
> --
> Andy Hutchinson
>
>
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