Re: [lto] PATCH: add more CALL_EXPR interfaces

[Sandra Loosemore <sandra at codesourcery dot com>]

Ian Lance Taylor wrote:
> Sandra Loosemore <sandra@codesourcery.com> writes:
>
> > I haven't yet changed the low-level representation of CALL_EXPRs to
> > actually have a variable number of operands.  My plan is to continue
> > to use struct tree_exp, and instead of stuffing a TREE_LIST of
> > arguments in operand 1, put an INT_CST node there that holds the
> > number of arguments following the fixed operands in the node.  It's a
> > little icky, but the storage overhead should be negligible (since
> > integer constants are shared) and it avoids having to special-case
> > CALL_EXPRs every place where compound expressions are being
> > manipulated.
>
> I assume this is a temporary maneuver, and that with the new
> representation the first operand will be an int, not an INT_CST node.

Well, no.  Giving these new beasts the same representation as other kinds of 
expressions using struct tree_exp means that existing places in the code -- tree 
walkers and the like -- that iterate over the operands of an expression don't 
need to be special-cased.  I think special-casing TREE_OPERAND to account for a 
different offset to the first "real" operand is a much messier and less 
efficient solution than maintaining a uniform representation and just treating 
the argument count itself as an (implicit) operand that needs to be unwrapped.

> >       default:
> > !       if (TREE_CODE_CLASS (code) == tcc_call)
> > ! 	return (sizeof (struct tree_exp)
> > ! 		+ (TREE_OPERAND_LENGTH (node) - 1) * sizeof (char *));
> > !       else
> > ! 	return tree_code_size (code);
> >       }
> >   }
>
> Why sizeof (char *)?  Why not sizeof (tree)?
>
> I see that TREE_VEC uses sizeof (char *), but that looks weird to me
> also.

Well, "why" is because I copied that expression verbatim from tree_code_size and 
just substituted TREE_OPERAND_LENGTH for TREE_CODE_LENGTH.  :-P  I can certainly 
make all these instances use sizeof (tree) instead.

-Sandra