On 9/20/2014 3:00 AM, Ola Fosheim Grostad wrote:
On Saturday, 20 September 2014 at 08:39:41 UTC, Walter Bright wrote:
E.g. TSX is coming even if there is
a bug in lower end CPUs. Suggest making performance oriented prototypes on
different architectures before concluding.
I'd love to see it.
A 128 bit CAS instruction is at about 19-25 cycles, but a transaction on the
other hand can by using xbegin/xend cover both refcounting, locking and rollback
of multiple objects so you need cooperation from code gen. Basically all changes
between xbegin/xend are kept in cache and written to memory upon success. On
failure you have a slower fallback.
I don't know what that leads to in amortized cost reduction, but 30-70% might be
possible if it is done right.
Please show me the inc/dec optimized x86 code.
As soon as you pass a reference to a function, that all goes out the window.
There's a reason why Rust has invested so much effort in the notion of a
"borrowed" pointer.
The pure @nogc crowd care less about safety, but you should be able to track
this using dataflow?
Suppose I pass a pointer to:
void foo(T* p);
How do I do dataflow?
3. True, but you can keep the refcount at a negative offset for new-based
allocations. Besides it only affects those who do @nogc and they should know
what they are doing.
If this is so simple, why doesn't everyone do it?
Never said performance and thread safe RC was easy. It is probably difficult to
get below 10 cycles for inc/dec pairs even with excellent code gen...? And
probably closer to 40 cycles for regular code gen. Just guessing.
The question was about mixing RC'd and non-RC'd objects.
