Re: RFA/ARM: Switch mode when setting PC

[Andrew Cagney <cagney at gnu dot org>]

> On Fri, Jan 16, 2004 at 09:10:40AM -0500, Daniel Jacobowitz wrote:
>
> > > The ari contains this yellow card:
> > > 
> > > write pc
> > > Replace write_pc() with get_frame_base_address or get_frame_id; at 
> > > present the inferior function call code still uses this when doing a 
> > > DECR_PC_AFTER_BREAK
> > > 
> > > the concern is with the way write_pc is being called to perform two 
> > > different operations:
> > > 
> > > - decrement the pc just after the target stops
> > > Arrrg!
> > > - jump to a specific address
> > > As with an inferior function call or jump.
> > > 
> > > I think it would be better to have two methods so that it's clear that 
> > > this case only applies when doing a jump.
>
> > Well, it'd be better to rip out the current DECR_PC_AFTER_BREAK and
> > handle it completely within the four (roughly) affected targets,
> > thereby removing the overloading of write_pc.  IMVHO.

It's been on everyones wish list for too long.  Last time I tried I got 
bogged down due to a lack of ia32 doco - that's now been fixed though.

> Hi Andrew,
>
> Is this patch OK (write_pc isn't deprecated yet!)?  Cleaning up the
> existing DECR_PC_AFTER_BREAK handling is going to be a touchy job, and
> I don't really want to try it today :)  I'll try to look into it later,
> though.

I was suggesting "two methods so that it's clear that this case only 
applies when doing a jump".  This won't involve anything like 
deprecating /removing decr_pc_after_break _+ write_pc but will involve 
the addition of a new method like:
	set_resume_address (arch, targ or tpid or regs)
that could somehow default to a legacy call to write_pc.  Significantly, 
this will avoid making the changes conditional on the elimination of 
decr-pc (your concern).

Why is this better?  It clearly separates the [apparently] legetimate 
resume case from the decr-pc case.  This in turn opens the way for the 
deprecate / delete decr-pc "write_pc" code while at the same time 
ensuring that the work can't break the arm.

enjoy,
Andrew