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Re: [PATCH] Fix PR56344


On Fri, Mar 01, 2013 at 09:41:27AM +0100, Richard Biener wrote:
> On Wed, Feb 27, 2013 at 6:38 PM, Joseph S. Myers
> <joseph@codesourcery.com> wrote:
> > On Wed, 27 Feb 2013, Richard Biener wrote:
> >
> >> Wouldn't it be better to simply pass this using the variable size handling
> >> code?  Thus, initialize args_size.var for too large constant size instead?
> >
> > Would that be compatible with the ABI definition of how a large (constant
> > size) argument should be passed?
> 
> I'm not sure.  Another alternative is to expand to __builtin_trap (), but that's
> probably not easy at this very point.
> 
> Or simply fix the size calculation to not overflow (either don't count bits
> or use a double-int).

I don't think double_int will help us here.  We won't detect overflow,
because we overflowed here (when lower_bound is an int):
  lower_bound = INTVAL (XEXP (XEXP (arg->stack_slot, 0), 1));
The value from INTVAL () fits when lower_bound is a double_int, but
then:
  i = lower_bound;
  ...
  stack_usage_map[i]
the size of stack_usage_map is stored in highest_outgoing_arg_in_use,
which is an int, so we're limited by an int size here.
Changing the type of highest_outgoing_arg_in_use from an int to a
double_int isn't worth the trouble, IMHO.

Maybe the original approach, only with sorry () instead of error ()
and e.g. HOST_BITS_PER_INT - 1 instead of 30 would be appropriate
after all.  Dunno.

	Marek


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