On 8/19/19 7:57 AM, Richard Biener wrote:
>
> +static tree
> +objsize_from_type (tree object)
> +{
> + if (TREE_CODE (object) != ADDR_EXPR)
> + return NULL_TREE;
> +
> + tree type = TREE_TYPE (object);
> + if (POINTER_TYPE_P (type))
>
> that if looks suspicious... I'd say
> if (!POINTER_TYPE_P (type))
> return NULL_TREE;
>
> is better
Sure. But we may not be able to use this anyway as you noted later,
depending on the type is not safe.
>
> + type = TREE_TYPE (type);
>
> + if (TREE_CODE (type) == ARRAY_TYPE && !array_at_struct_end_p (object))
> + {
>
> array_at_struct_end_p will never return true here since you pass it
> an ADDR_EXPR... you wanted to pass TREE_OPERAND (object, 0) here?
I think you're right. Given this was cribbed from the tail of another
function elsewhere, I suspect that other function has the same issue.
I suspect ultimately we want to fix that other copy and drop
objsize_from_type.
>
> Also you seem to use this info to constrain optimization when you
> might remember that types of addresses do not carry such information...
> Thus it should be "trivially" possible to write a testcase that is miscompiled
> after your patch. I also don't see this really exercised in the
> testcases you add?
Arggh. You're absolutely correct. I must be blocking out that entire
discussion from last summer due to the trama :-)
If the destination is the address of a _DECL node, can we use the size
of the _DECL?
> All of them reference a static array a ...
>
> + if (TREE_CODE (size) != INTEGER_CST)
>
> TREE_CODE (size) == SSA_NAME you want
Agreed. Will fix.
jeff
