Multiple return values...

[Artur Skawina]

On 03/16/12 01:03, H. S. Teoh wrote:
> On Fri, Mar 16, 2012 at 12:11:44AM +0100, Simen Kjærås wrote:
>> On Thu, 15 Mar 2012 23:44:09 +0100, foobar <foo at bar.com> wrote:
>>
>>> Is swap usually inlined by the compiler?
>>
>> This is the body of swap for simple types:
>>
>>   auto tmp = lhs;
>>   lhs = rhs;
>>   rhs = tmp;
>>
>> For more complex types:
>>
>>   ubyte[T.sizeof] t = void;
>>   auto a = (cast(ubyte*) &lhs)[0 .. T.sizeof];
>>   auto b = (cast(ubyte*) &rhs)[0 .. T.sizeof];
>>   t[] = a[];
>>   a[] = b[];
>>   b[] = t[];
>>
>> So yeah. If that's not inlined, something's wrong.
> 
> Ideally, though, a swap of large objects should be a single loop of xchg
> instructions (in x86 anyway, xchg may not exist on other architectures).
> Unless dmd is much more clever than I thought, the above code would
> generate 3 loops, which uses more memory and is (probably) slower.

x86 xchg w/ mem ref implies lock, plus you'd have to load and store one
of the operands anyway.

artur