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

[HutchinsonAndy]

As you describe is exactly what I am concerned about!


"Ben L. Titzer" <address@hidden> wrote:

>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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>======================================================
>Imagination is more important than knowledge.
>-- Albert Einstein
>
>


-- 
Andy Hutchinson


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