[patch/RFA] multiarch INSTRUCTION_NULLIFIED

[Andrew Cagney]

Randolph Chung wrote:
>>>well, first i want to understand the problem. because i'm still not 
>>>yet 100% convinced that step_through_delay will work. simply using the
>>>"instruction_nullified" method in hppa-tdep as the "step_through_delay"
>>>method certainly is not working...
>>
>>When doing a stepi?  step_through_delay certainly won't help when it 
>>comes to doing a backtrace from the nullified instruction.
> 
> 
> when doing a step.

I was thinking that STEPI might be easier to debug :-)

Anyway, trying modifying gdbarch_read_pc and unwind_pc (I suspect you 
need to modify both - which is a bug) to read something like:

	if (instruction nullified)
		return next-pc
	else
		return this-pc

it should fool GDB into thinking that it's one instruction ahead of itself.

Andrew