but how do you determinate the end pc ?

Scan the bytecodes.  See Cogit>scanMethod.
 


Hi Eliot. It seems I am still far away from understanding scanMethod. I cannot figure out how you get the endPC. I see you only set it in this part:
(descriptor isReturn
         and: [pc >= latestContinuation]) ifTrue:
            [endPC := pc].

anyway, I trust you :)

The first return beyond the furthest continuation is the end of the method.  The furthest continuation is the furthest forward we've seen a branch.  If we see a return beyond all branches that return must be the end of the method.

e.g.
    expr ifTrue: [^foo] ifFalse: [self bar]. ^self

the first ^foo is not the end of the method because there's a branch around it from the expr test to the start of [self bar].  But the last ^self is the end because there's no branch past it.
 

ahhh got it now :)
Thanks Eliot for the explanation. Now I also understand why you call it "scan" hahaha.


 


 

 
if the method's byte codes are greater than some limit, e.g. 1024 bytes of bytecodes.  It then rejects the method if the actual end pc is greater than some limit that we find empirically causes the JIT to crash because of the size of the alloca.


Cheers



 
 

thanks!
 
the same experiment with StackVM works fine.
Of course in a normal image (without this experiment) I can do PolymorphSystemSettings showDesktopLogo: true. without problems.


From gdb i see:

(gdb) bt
#0  0x0000a190 in compileCogMethod (selector=528828260) at /Users/mariano/Pharo/VM/git/cogVMBlessedSSH/blessed/build/../src/vm/cogit.c:3601
#1  0x00009088 in cogselector (aMethodObj=531503072, aSelectorOop=528828260) at /Users/mariano/Pharo/VM/git/cogVMBlessedSSH/blessed/build/../src/vm/cogit.c:3129
#2  0x0003268b in ceSendsupertonumArgs (selector=528828260, superNormalBar=0, rcvr=536158520, numArgs=0) at /Users/mariano/Pharo/VM/git/cogVMBlessedSSH/blessed/build/../src/vm/gcc3x-cointerpmt.c:11007
#3  0x1f40006c in ?? ()
#4  0x00067350 in threadSchedulingLoop (vmThread=0x1030c00) at /Users/mariano/Pharo/VM/git/cogVMBlessedSSH/blessed/build/../src/vm/gcc3x-cointerpmt.c:44006
#5  0x0003d2cb in initialEnterSmalltalkExecutive () at /Users/mariano/Pharo/VM/git/cogVMBlessedSSH/blessed/build/../src/vm/gcc3x-cointerpmt.c:17788
#6  0x0003df8f in initStackPagesAndInterpret () at /Users/mariano/Pharo/VM/git/cogVMBlessedSSH/blessed/build/../src/vm/gcc3x-cointerpmt.c:18208
#7  0x00022618 in interpret () at /Users/mariano/Pharo/VM/git/cogVMBlessedSSH/blessed/build/../src/vm/gcc3x-cointerpmt.c:2066
#8  0x0006dc60 in -[sqSqueakMainApplication runSqueak] (self=0x1d0ca60, _cmd=0x124ebf) at /Users/mariano/Pharo/VM/git/cogVMBlessedSSH/blessed/build/../platforms/iOS/vm/Common/Classes/sqSqueakMainApplication.m:174
#9  0x93ad586c in __NSFirePerformWithOrder ()
#10 0x908b8dd2 in __CFRunLoopDoObservers ()
#11 0x90874ced in __CFRunLoopRun ()
#12 0x908743c4 in CFRunLoopRunSpecific ()
#13 0x908741f1 in CFRunLoopRunInMode ()
#14 0x97760e04 in RunCurrentEventLoopInMode ()
#15 0x97760af5 in ReceiveNextEventCommon ()
#16 0x97760a3e in BlockUntilNextEventMatchingListInMode ()
#17 0x96d1a595 in _DPSNextEvent ()
#18 0x96d19dd6 in -[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] ()
#19 0x96cdc1f3 in -[NSApplication run] ()
#20 0x96cd4289 in NSApplicationMain ()
#21 0x0006b9f9 in main (argc=1, argv=0xbffff688, envp=0xbffff690) at /Users/mariano/Pharo/VM/git/cogVMBlessedSSH/blessed/build/../platforms/iOS/vm/Common/main.m:52


And the line that fails is:     allocateOpcodesbytecodes((numBytecodes + extra) * 10, numBytecodes);

numBytecodes is 49729 and extra is 10.

Any idea?

thanks!

--
Mariano
http://marianopeck.wordpress.com




--
Mariano
http://marianopeck.wordpress.com




--
Mariano
http://marianopeck.wordpress.com





--
best,
Eliot





--
Mariano
http://marianopeck.wordpress.com





--
best,
Eliot





--
Mariano
http://marianopeck.wordpress.com





--
best,
Eliot





--
Mariano
http://marianopeck.wordpress.com





--
best,
Eliot





--
Mariano
http://marianopeck.wordpress.com