On Tue, Aug 30, 2011 at 5:01 PM, Aldy Hernandez <[email protected]> wrote:
> [I'm going to respond to this piece-meal, to make sure I don't drop
> anything. My apologies for the long thread, but I'm pretty sure it's in
> everybody's kill file by now.]
>
>> + /* Be as conservative as possible on variable offsets. */
>> + if (TREE_OPERAND (exp, 2)
>> +&& !host_integerp (TREE_OPERAND (exp, 2), 1))
>> + {
>> + *byte_offset = TREE_OPERAND (exp, 2);
>> + *maxbits = BITS_PER_UNIT;
>> + return;
>> + }
>>
>> shouldn't this be at the very beginning of the function? Because
>> you've set *bit_offset to an offset that was _not_ calculated relative
>
> Sure. I assume in this case, *bit_offset would be 0, right?
It would be DECL_FIELD_BIT_OFFSET of that field. Oh, and
*byte_offset would be
*byte_offset = size_binop (MULT_EXPR, TREE_OPERAND (exp, 2),
size_int (DECL_OFFSET_ALIGN
(field) / BITS_PER_UNIT));
see expr.c:component_ref_field_offset () (which you conveniently
could use here).
Note that both TREE_OPERAND (exp, 2) and compoment_ref_field_offset
return offsets relative to the immediate containing struct type, not
relative to the base object like get_inner_reference does ...
(where it is still unclear to me what we are supposed to return from this
function ...)
Thus, conservative would be using get_inner_reference here, if the
offset is supposed to be relative to the base object.
Richard.
