PC_REGNUM in dwarf2-frame.c

[Andrew Cagney <ac131313 at redhat dot com>]

Hello,

I'm trying to figure out what to do with PC_REGNUM in:

>   /* Save the register info in the cache.  */
>   for (reg = 0; reg < fs->regs.num_regs; reg++)
>     {
>       int regnum;
>
>       /* Skip the return address column.  */
>       if (reg == fs->retaddr_column)
> 	continue;
>
>       /* Use the GDB register number as index.  */
>       regnum = DWARF2_REG_TO_REGNUM (reg);
>
>       if (regnum >= 0 && regnum < num_regs)
> 	cache->reg[regnum] = fs->regs.reg[reg];
>     }
>
>   /* Store the location of the return addess.  If the return address
>      column (adjusted) is not the same as gdb's PC_REGNUM, then this
>      implies a copy from the ra column register.  */
>   if (fs->retaddr_column < fs->regs.num_regs
>       && fs->regs.reg[fs->retaddr_column].how != REG_UNSAVED)
>     cache->reg[PC_REGNUM] = fs->regs.reg[fs->retaddr_column];
>   else
>     {
>       reg = DWARF2_REG_TO_REGNUM (fs->retaddr_column);
>       if (reg != PC_REGNUM)
> 	{
> 	  cache->reg[PC_REGNUM].loc.reg = reg;
> 	  cache->reg[PC_REGNUM].how = REG_SAVED_REG;
> 	}
>     }

Rather than trying to map regaddr_column onto PC_REGNUM I think it 
should handle it directly vis:

- don't try to do a DWARF2_REG_TO_REGNUM() on it
- use frame_pc_unwind(next_frame) when it's unwound value is needed
- make frame_pc_unwind per-frame (again)?

The problem with PC_REGNUM is that it may not be a hard register.

Thoughts? (all my favorite architectures use stabs so I've not much to 
test this on).

Andrew