Re: [patch/RFA] multiarch INSTRUCTION_NULLIFIED

[Andrew Cagney <cagney at gnu dot org>]

Daniel Jacobowitz wrote:
> On Tue, Nov 30, 2004 at 10:19:24PM -0800, Randolph Chung wrote:
>
> > i experimented with another proposal which is to adjust the pc when we
> > are at a nullified instruction. i modified target_read_pc () to return
> > the previous (or next) pc when we are at a nullified instruction. this 
> > fixes some of the failures but causes new failures with the 
> > "recurse.exp" test. i need to investigate that some more. but teaching 
> > target_read_pc() to lie about the current pc seems to be suboptimal.
> >
> > lastly a comment about sparc -- i think the sparc case is simpler
> > because it doesn't have conditional nullification. so looking at a
> > particular insn you can always determine if the next insn will be
> > nullified or not. this is not always the case for hppa.
>
>
> Randolph,
>
> Here's an off-the-cuff idea for you.  Could you actually skip the
> nullified instruction, if you had a hook in the right place?  That is,
> when a thread stops, if it is stopped at a nullified instruction,
> forcibly move it to the next instruction before returning control to
> GDB.

Read the discussion between Randolf and myself.  This doesn't work for 
core files.

> This is probably not feasible if you have to use single-stepping to end
> up in the right place.  If you can compute the right place and adjust
> registers, though, it shouldn't be hard.

Andrew