A quest to unify web games and stand alone development
Flash is the most popular game platform on the web. OpenGL in C++ is the most widespread fully accelerated gaming platform for downloads. Is it possible to target both platforms from the one code base? I think so...
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Decompiling the differences
I have created about the simplest test I can, the “SimpleLoop” programmes. AS3 version HaXe version The difference in performace is dramatic – 10 to 20 fold. But all is not as bad as it seems…
I have been looking at the very interesting tool, abcdump.exe, as described here.
You can really get a feel for the differences between the outputs. And there is a simple explaination for the differences in file size – haXe includes a small library in the SWF. Fair enough.
I will concentrate on the “Run2″ test – both using “while” loops, rather than “for” loops. HaXe’s iterator-style for loops are slower than its while style loops – I’m hoping that this will not always be the case [Edit: actually the timings both vary and seem about the same]. (Although as a side note, I hope haXe will support both styles of for loops, since it makes porting easier amongst other reasons).
A quick look at the decompile of the Run2 function (two nested while… loops) shows the use of the command “iflt”, presumably “if less than”, which seems ideal for these loops. HaXe uses 3 statements here: coerce_a, lessthan, iffalse. I believe that haXe could easily use this optimisation, especially considering the for(i in 1…1000) style syntax. Also the increment operation. AS3 uses “inclocal_i”, where haXe uses 4 statements: getlocal, increment, coerce_a, setlocal. Again some low-hanging fruit for haXe to pick up.
Another trick is “pushshort” rather than “pushint” where size will allow, and it seems haXe integer constants are followed by “coerce_a”, whereas AS3 ones are not. AS3 used “convert_i” whereas haXe uses “coerce_a”. I’m not sure of the performace implications of this.
So, after some initial doubts, now I think haXe could get about a 10 fold increase in speed (in these very tight loops) pretty easily. HaXe (especially for flash 9) is very new, and I’m condifent these optimisation will come soon enough.
AS3 haXe function Run2():int /* disp_id 0*/ { // local_count=4 max_scope=1 // max_stack=2 code_len=60 0 getlocal0 1 pushscope 2 pushbyte 0 4 setlocal1 5 pushbyte 0 7 setlocal2 8 pushbyte 0 10 setlocal3 11 pushbyte 0 13 setlocal1 14 pushbyte 0 16 setlocal2 17 jump L1 L2: 21 label 22 pushbyte 0 24 setlocal1 25 pushbyte 0 27 setlocal3 28 jump L3 L4: 32 label 33 getlocal1 34 getlocal3 35 add 36 convert_i 37 setlocal1 38 inclocal_i 3 L3: 40 getlocal3 41 pushshort 10000 44 iflt L4 48 inclocal_i 2 L1: 50 getlocal2 51 pushshort 1000 54 iflt L2 58 getlocal1 59 returnvalue }function Run2():* /* disp_id 0*/ { // local_count=4 max_scope=1 // max_stack=2 code_len=70 0 getlocal0 1 pushscope 2 pushbyte 0 4 coerce_a 5 setlocal1 6 pushbyte 0 8 coerce_a 9 setlocal2 10 jump L1 L2: 14 label L1: 15 getlocal2 16 pushint 1000 // 0x3e8 18 coerce_a 19 lessthan 20 iffalse L3 24 pushbyte 0 26 coerce_a 27 setlocal1 28 pushbyte 0 30 coerce_a 31 setlocal3 32 jump L4 L5: 36 label L4: 37 getlocal3 38 pushint 10000 // 0x2710 40 coerce_a 41 lessthan 42 iffalse L6 46 getlocal1 47 getlocal3 48 add 49 coerce_a 50 setlocal1 51 getlocal3 52 increment 53 coerce_a 54 setlocal3 55 jump L5 L6: 59 getlocal2 60 increment 61 coerce_a 62 setlocal2 63 jump L2 L3: 67 getlocal1 68 returnvalue 69 returnvoid }