Properties: a.b.c = 3

[Benji Smith]

Chad J wrote:
> Chad J wrote:
>> Bill Baxter wrote:
>>> On Wed, Jul 29, 2009 at 1:14 PM, grauzone<none at example.net> wrote:
>>>> Chad J wrote:
>>>>> Thinking about it a little more, the extra temporaries could run you out
>>>>> of registers.  That still sounds like a negligable cost in most code.
>>>> Temporaries can be on the stack. That's not a problem.
>>>>
>>> How is that not a performance issue?  The stack is in main memory.
>>>
>>> --bb
>> This is where my knowledge starts to run a bit thin.
>>
>> So correct me if I'm wrong, but isn't something like the stack (or at
>> least the top/bottom/end in use) extremely likely to be in the nearest
>> cache (L1)?
>>
>> If that's the case, then this kind of dereference is going to be of the
>> cheaper variety.
> 
> Also, really deep dot chains are unlikely to happen.  I just feel like
> this won't create many more memory accesses than there were already.
> Especially for people with 64 bit OSes on x86_64 that are not register
> starved like the 32 bit x86.  On x86 you are hitting the stack all the
> time anyways, and the extra access or two will go unnoticed.

Especially especially because, if you prevent the a.b.c = x syntax, the 
only thing that'll happen is you'll cause people to write all that code 
themselves. The same number of assignments will happen anyhow, but the 
user will have to write them all manually. I'll all for having the 
compiler automate the boilerplate stuff.

Also, note that the double-assignment case only happens when assigning 
to value types. Assigning to reference type properties will be unaffected.

--benji