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What's News in the PlayBasic world ? - Find out here.
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PlayBasic V1.64P and PlayBasic To DLL Latest News
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By: Kevin Picone Added: May 1st, 2014
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Category: All,Update,Tools,Machine Code
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The following is a selection of blog posts from the development of PlayBasic to DLL (Machine code translator) and the parallel upgrade PlayBasic V1.64P
PlayBasic V1.64P Beta 38 - Loopy Loops (April 17, 2014)
After much head scratching it was decided that the VM's instruction set needed a few alterations with it's looping instructions. These changes are two fold, the parser now does a better job at producing cleaner input parameter data and the instructions produced are now more stream lined. Producing better code, is better for everything down the line from running the code through the VM and thus any translations. The translation stuff is really why these changes need to be made now, since the original parser would use generic instructions where some data was pre-computed. From the translators perspective, this made it very difficult to accurately detect those loops in a single pass.
Today's changes introduce some new high level instructions to the VM. These changes make it trivial to accurately pin point the set up code in a FOR/NEXT looping blocks. I've already added a decoder to PB2DLL which locates the new opcodes and builds a export string in the dissassembly. The detection and output are working fine, but it's here that I noticed there's a few extra moves creating into the output code than need be. Which mostly happens when a loop is using literals. In previous editions the parser would drop an extra move prior to the loop entry point. The same can happen in the destination value expressions also. These things are easily tweaked out, just hadn't noticed them before.
PlayBasic V1.64P Beta 38 - For / Next Loop updates (April 22, 2014)
If you didn't already know, it's been Easter holidays here which has just come to a close, so only started firing up the compilers today. Last time I was working on the tuning the compiler and VM to use the new looping setup codes for FOR/NEXT loops. These changes have were translated across to PB2DLL when I was happy with the new structures. The changes are much easier for PB2LL parser to accurately detect what's going on in the program in regards to loops. But not only that, the new format allows us to make more optimizations to the assembly.
Tonight I've been back working on the parser in the PlayBasic compiler, as when converting the code to assembly, there's often these extra move operations that would end up in the byte code first and thus translated assembly. Surprisingly it generally happened what a for loop's (start / end) were both literal. For some reason it'd drop them into temps and then pull them into the loop structures internal registers. Which appears to be some left over instruction set behaviors that are no longer necessary. Older versions of the VM worked differently than today, in particular when dealing with literals. Now they can be treated just like variables, so don't they need to be treated special ways.
Something you might not be aware of is that when a for/loop is started, there's a comparison between the Start and End of loop. If Start is bigger than the end, the execution jumps to the beyond the matching next.
For example,
For lp =0 to 100
print lp
next
So there's an indivisible screening wrapped around loop entry, which might look at like this in PB style code.
if 0<=100
For lp =0 to 100
print lp
next
endif
One of the new benefits of the FOR/NEXT replacement opcodes, is the export parser can detect constant behaviors and produce code accordingly. So the comparison behind the Start /End loop counters can actually be made at compile time when they're both literal. Removing those lead in comparisons from the output code. The same goes for the storing them in internal VM registers, saving more set up code.
Being able to trap literals helps with STEP loops also. When a variable is used in for/next/step loop, the looping structure has constantly query what sign the STEP, then clip the loop counter based upon it. If the sign of step is known at compile time, then the loop can be created with this knowledge ahead of time. Removing more redundancy from the final translated assembly (in PB2DLL)
PB is pretty flexible with FOR/NEXTS allowing integer and floating point counters with variable step directions in both. People rarely use floating point loops, but since the VM supports it, the exported assembly through PB2DLL should also. Dropped in the standard by one loop structure earlier today and have just started adding the variable STEP stuff with floats. It's painful purely because of the horrible fpu instruction set in x86 chips...
PlayBasic To Dll - Tweaking Looping Constructs ( April 24, 2014)
The past day or so I've been wrestling with FOR/NEXT/STEP implementation in the translator of all things. Those reading the PB1.64P upgrade blog lately would no doubt be aware that the compiler/VM side has recently changed, the changes were explicitly made to facilitate an easier more accurate translation to machine code from the byte code origin. When porting the changes across to PB2DLL I noticed that it only supported Integer FOR/NEXT looping structures, where as the VM supports integer and floating point look structures
Floating point loops present a bit of a problem due to the FPU's rather awful implementation, but really that's everything floating point in these things. Writing the translator code isn't difficult, it's just that it needs extra steps when dealing with floats which feels rather awkward. Knowing this, invested some time into the PB compiler to make sure the compiler side cleans out any unnecessary steps when setting up the loop and gives enough information to easily work out how to set the loop and what kind of set up is needed. The decoder is able to pick up short cut situations where you used literals in your For Next Statement and cut down amount of screen code needed, in some cases on screening is need. Since the loops duration can be validated at compile time. It's those little things that help fine tune the performance of the final machine code.
The big question is when do we release ? - Well since both sides need to be in alignment for the resulting DLL's work, the original plan was to release them both together, but I think we might release PB2DLL first.. This will help further test the translation in real world situations. Of course that'll most likely mean that there will be a few updates made prior to the release, but there's not that can be done about it. It now just needs people other than me testing it.
PlayBasic To Dll - Exporting LinkDLL binding code ( April 28, 2014)
Had a few short programming (testing mainly) sessions over the weekend. Up until now, I've been testing the translator from the PB IDE. So in order to run it, i've got to compile and run as normal (F5), but as release time nears, we need to be able to build it into a final EXE, but it's here we ran into a new problem, where the exported internal structures could stop the exe from running. I though this might happen, given how much of the PB VM internals have changed over the last 6 months. Tracking down the issue took a while, but was fairly easy to solve which is a good thing. So now I can build & run PB2DLL in exe form and it works as normal.
Once the build problem was sorted, i've been getting back to the GUI and internal exporter functions. For the first version(s) I'm not going to bother with adding switching over the assembly code generation/optimization, it'll just do it silently. There are times when that wouldn't be wanted, but can't foresee anybody running into such problems. Which means for the time being some of the GUI toggles have been ripped. The only option that is useful is the Export LINKDLL code option. This option gets the translator to build a chunk of the PlayBasic source code that handles the function binding to the newly created DLL.
Linking to DLL's is something of a mystery for most people, basically all that happens is the PB compiler/VM create interfaces to external machine code that look and act like normal PB functions in your program. There's some limitations in current versions of PB as to what data type/structures you can pass into and out of them, but those will be tweaked out in time. In order to use our newly converted DLL's in our PlayBasic programs, it stands to reason that we'd need to know how to write the LinkDLL binding code for the functions we wish to use. Which was true yesterday, but now the translator can build a template of the exported functions for you in PlayBasic code. Obviously there's some limits in terms of data types that it currently supports, which stem from the PB compiler side not supporting passing PB internal structures through to external code. Why? - because nothing other than PB understands PB internal structures, making supporting that originally point less.
To test the LinkDLL exporting, added a few bogus functions to the common point rotation demo and here's what we get.
; ---------------------------------------------------------------------
; ---------------------------------------------------------------------
; ---- [cube.dll ]---------------------------------------
; ---- [ Created:28 Apr 2014 ]---------------------------------------
; ---------------------------------------------------------------------
; ---------------------------------------------------------------------
linkDll "cube.dll"
dll_addintegers(a,b) alias "dll_addintegers" as Integer
dll_addfloats(a#,b#) alias "dll_addfloats" as Float
dll_addstrings(a$,b$) alias "dll_addstrings" as String
DrawCube(sections,spacing,scale#) alias "dll_rotate_vertex_cube_9mult_common_point"
DrawCube_opt1(sections,spacing,scale#) alias "dll_rotate_vertex_cube_9mult_common_point_opt1"
DrawCube_opt2(sections,spacing,scale#) alias "dll_rotate_vertex_cube_9mult_common_point_opt2"
EndlinkDll
This code can either get cut'n'pasted in your project or #included. Either way once it's in and assuming PB can find your DLL (it's in the project folder) then your away in the machine code era!
What might be a good is to get PB2DLL to mangle the export names in the DLL. So if you have a function called "AddIntegers", the external name can be mangled into some random hash, such as 'ABHDGSNFSSF' - This would mean that exported linkDLL codes must match the build of dll exactly, as if the alias names don't match, windows can't local the machine code function and it won't run ! It'd only be helpful to prevent snoops from look at your function names and potentially working out the parameters.
PlayBasic V1.64P BETA #39 (Retail Beta) (30th,Apr,2014)
Beta #39 introduces a bunch of subtle but equally important changes, starting with the newly replaced FOR/NEXT/STEP parser and VM instruction set, there's also a few changes to the VM close down behavior. The close down changes are due to a strange issue i've been having with PB2DLL where the PB2DLL EXE would crash on exit when the program wasn't registered (worked fine once you entered your serial).
So I've been chasing the close down issue most of the day, it appears that some typed arrays can somehow contained data that wasn't a typed array container. How that's the possible is a mystery at the moment, but I've included some more screening in the clean up code to make sure it's releasing the array an not some of random bank of that data that something else was/is using. Getting this right is more important now than ever, thus is because of the way type deletion works in the runtime, so we have to make sure it's releasing data that makes sense, as if it doesn't it'll die.
The real question is how is the bad array data was/is getting into the arrays in the first place, which i'm not 100% on at this point. So i've added some debug messages to the debugger console (F7 to run, then click on the console tab) to help the community track where else these quirks put up.. Does it happen at runtime ? or only closing down the VM..
So get testing !!!!!!
Download
Download PlayBasic V1.64P Beta 39
More Information
For the full picture/ screen shots etc see the PlayBasic 2 DLL development blog
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