Re: [patch/RFA] multiarch INSTRUCTION_NULLIFIED

Andrew Cagney
2004-12-01T21:25:04Z

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