Re: Patch to fix gcc.c-torture/compile/20010102-1.c on IA64 HP-UX

[Jeff Law <law@redhat.com>]

Peter Bergner wrote:
> On Tue, 2008-09-16 at 13:14 -0600, Jeff Law wrote:
>   
>> You don't necessarily need to set REG_POINTER on hard registers, and in 
>> general it's unwise.
>>
>> What we do  is we set REG_POINTER on appropriate pseudos within the RTL 
>> for the pseudo.  Then after register allocation/reloading, alter_reg 
>> changes the REGNO field for the pseudo to turn it into a hard register.  
>> Note this preserves the REG_POINTER flag so that you can test it after 
>> reload. 
>>
>> So you'll need to look into where that insn was created and ensure that 
>> the appropriate pseudo has REG_POINTER set (r699)  Then verify that it 
>> was carried forward through allocation/reloading.
>>
>> REG_POINTER, when set, indicates the object is a pointer for its entire 
>> lifetime -- thus setting it on hard registers is generally a bad idea 
>> and it's only safe under certain circumstances on pseudos, particularly 
>> in the presence of cross jumping.
>>     
>
> So something similar to this untested patch to fix Steve's problem?
> (This assumes ORIGINAL_REG (reg) == reg if reg is a psuedo.  Maybe it
> isn't. :)
>
> Peter
>
> --- config/ia64/predicates.md	(revision 140251)
> +++ config/ia64/predicates.md	(working copy)
> @@ -585,6 +585,6 @@ (define_predicate "ar_pfs_reg_operand"
>  (define_predicate "basereg_operand"
>    (match_operand 0 "register_operand")
>  {
> -  return REG_P (op) && REG_POINTER (op);
> +  return REG_P (op) && REG_POINTER (regno_reg_rtx[ORIGINAL_REGNO
> (op)]);
>  })
>
>   
But this shouldn't be necessary.  REG_POINTER is set within the RTX for 
the original pseudo and alter_reg (via changing REGNO) preserves the 
setting for use post-reload, even though we're looking at a hard register.

My recommendation for Steve is the same.  First ensure that REG_POINTER 
is set on the appropriate REG within the insn when the insn is created, 
then go forward and pinpoint where it disappears as the disappearance is 
a bug.
Jeff