On 3/7/2013 9:36 AM, Johannes Pfau wrote:
I'm sorry I have to pester you with this again, but I still have some
questions regarding POD types and I'd like to fix this in GDC.
So from last discussion:
>> Wouldn't it be legal to still pass non-PODs in registers when calling
functions and only copying them back to
>> the stack if the address is needed? As we pass structs by value anyway, how
could this be problematic?
>
> No, not allowed. Consider why there are copy constructors, and what they do.
I compiled some test programs with dmd and dmd _does_ pass non-POD values in
registers as I suggested above.
See this example:
https://gist.github.com/jpf91/5064703 (D)
https://gist.github.com/jpf91/5064764 (ASM)
That's because objects with constructors are now regarded as POD.
I also don't understand how a copy ctor could break this.
Because a copy ctor executes arbitrary code, and this just does not work in the
general case if a value is in a register.
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