GC vs. Manual Memory Management Real World Comparison

[Iain Buclaw]

On 7 September 2012 07:28, Sven Torvinger <Sven at torvinger.se> wrote:
> On Thursday, 6 September 2012 at 20:44:29 UTC, Walter Bright wrote:
>>
>> On 9/6/2012 10:50 AM, Benjamin Thaut wrote:
>>>
>>> I just tried profiling it with Very Sleepy but basically it only tells me
>>> for
>>> both versions that most of the time is spend in gcx.fullcollect.
>>> Just that the GDC version spends less time in gcx.fullcollect then the
>>> DMD version.
>>
>>
>> Even so, that in itself is a good clue.
>
>
> my bet is on, cross-module-inlining of bitop.btr failing...
>
> https://github.com/D-Programming-Language/druntime/blob/master/src/gc/gcbits.d
>
> version (DigitalMars)
> {
>     version = bitops;
> }
> else version (GNU)
> {
>     // use the unoptimized version
> }
> else version (D_InlineAsm_X86)
> {
>     version = Asm86;
> }
>
> wordtype testClear(size_t i)
> {
>   version (bitops)
>   {
>     return core.bitop.btr(data + 1, i);   // this is faster!
>   }
>

You would be wrong.  btr is a compiler intrinsic, so it is *always* inlined!

Leaning towards Walter here that I would very much like to see hard
evidence of your claims.  :-)


On a side note of that though, GDC has bt, btr, bts, etc, as
intrinsics to its compiler front-end.  So it would be no problem
switching to version = bitops for version GNU.


-- 
Iain Buclaw

*(p < e ? p++ : p) = (c & 0x0f) + '0';