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Re: [RFA] [tree-optimization/80576] Handle non-constant sizes in DSE
On 8/22/19 4:46 AM, Richard Biener wrote:
>>> 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?
>
> Yes, but this should already happen for both invariant ones like &a.b.c
> and variant ones like &a.b[i].c in ao_ref_init_from_ptr_and_size.
I don't see that in ao_ref_init_from_ptr_and_size. AFAICT if you don't
know the size when you call that routine (size == NULL), then you end up
with the ref->size and ref->max_size set to -1.
Am I missing something here?
Jeff