Hi all,
I'm stumped by the main interpreter loop: As I can't seem to get my hands on the currently executing bytecodes using the context-step simulator (same issue as desribed in http://bugs.squeak.org/view.php?id=5716), I thought I'd log them along the way directly in the VM.
However, modifying the interpreter loop to:
while (1) { printNumtoFile(currentBytecode, foo->vmLogFile); switch (currentBytecode) { .. } }
didn't work: printNumtoFile() gets executed exactly once. I've debugged this with GDB: currentBytecode gets modified from within the CASE statements and the program never gets past the switch() statement.
I wouldn't want to maintain the same code in all bytecode CASEs but I can't think of another solution at the moment.
Is there any other way to examine the currently executing bytecodes apart from the buggy ContextPart?
Thanks, André
Hi,
On 11/9/07, André Wendt andre.wendt@hpi.uni-potsdam.de wrote:
However, modifying the interpreter loop to:
while (1) { printNumtoFile(currentBytecode, foo->vmLogFile); switch (currentBytecode) { .. } }
didn't work: printNumtoFile() gets executed exactly once. I've debugged this with GDB: currentBytecode gets modified from within the CASE statements and the program never gets past the switch() statement.
that's most certainly because you are using a GNUified version of the interpreter (right?). That one applies threading to the interpreter implementation, so the loop body is not actually executed like a loop body usually is. Instead, interpreter logic jumps directly to and fro in the bytecode routines.
Best,
Michael
On Nov 9, 2007, at 1:13 PM, Michael Haupt wrote:
Hi,
On 11/9/07, André Wendt andre.wendt@hpi.uni-potsdam.de wrote:
However, modifying the interpreter loop to:
while (1) { printNumtoFile(currentBytecode, foo->vmLogFile); switch (currentBytecode) { .. } }
didn't work: printNumtoFile() gets executed exactly once. I've debugged this with GDB: currentBytecode gets modified from within the CASE statements and the program never gets past the switch() statement.
that's most certainly because you are using a GNUified version of the interpreter (right?). That one applies threading to the interpreter implementation, so the loop body is not actually executed like a loop body usually is. Instead, interpreter logic jumps directly to and fro in the bytecode routines.
Intresting could you explain how? Also how to solve the problem?
Best,
Michael
Mth
On Nov 9, 2007, at 14:10 , Mathieu Suen wrote:
On Nov 9, 2007, at 1:13 PM, Michael Haupt wrote:
Hi,
On 11/9/07, André Wendt andre.wendt@hpi.uni-potsdam.de wrote:
However, modifying the interpreter loop to:
while (1) { printNumtoFile(currentBytecode, foo->vmLogFile); switch (currentBytecode) { .. } }
didn't work: printNumtoFile() gets executed exactly once. I've debugged this with GDB: currentBytecode gets modified from within the CASE statements and the program never gets past the switch() statement.
that's most certainly because you are using a GNUified version of the interpreter (right?). That one applies threading to the interpreter implementation, so the loop body is not actually executed like a loop body usually is. Instead, interpreter logic jumps directly to and fro in the bytecode routines.
Intresting could you explain how?
It replace each "case 123:" with a label and each "break" with "goto *jumpTable[currentBytecode]", and initializes the jumpTable with the labels.
Also how to solve the problem?
Modify the BREAK macro in sqGnu.h.
- Bert -
Hi Mathieu,
On 11/9/07, Mathieu Suen mathk.sue@gmail.com wrote:
Intresting could you explain how?
there is a nice paper co-authored by Ian that does a better job in explaining this (and much more) than I possibly could given the little time I have right now... http://www.daimi.au.dk/~ups/OOVM/papers/piumarta-riccardi:threaded.pdf
The paper describes several flavours of threaded interpretation.
Also how to solve the problem?
Bert has answered this question, I think.
Best,
Michael
On Nov 9, 2007, at 2:30 PM, Bert Freudenberg wrote:
On Nov 9, 2007, at 14:10 , Mathieu Suen wrote:
On Nov 9, 2007, at 1:13 PM, Michael Haupt wrote:
Hi,
On 11/9/07, André Wendt andre.wendt@hpi.uni-potsdam.de wrote:
However, modifying the interpreter loop to:
while (1) { printNumtoFile(currentBytecode, foo->vmLogFile); switch (currentBytecode) { .. } }
didn't work: printNumtoFile() gets executed exactly once. I've debugged this with GDB: currentBytecode gets modified from within the CASE statements and the program never gets past the switch() statement.
that's most certainly because you are using a GNUified version of the interpreter (right?). That one applies threading to the interpreter implementation, so the loop body is not actually executed like a loop body usually is. Instead, interpreter logic jumps directly to and fro in the bytecode routines.
Intresting could you explain how?
It replace each "case 123:" with a label and each "break" with "goto *jumpTable[currentBytecode]", and initializes the jumpTable with the labels.
Cool! I had never known what the gnuifier was doing. thanks
Also how to solve the problem?
Modify the BREAK macro in sqGnu.h.
- Bert -
vm-dev@lists.squeakfoundation.org
-
André Wendt -
Bert Freudenberg -
Mathieu Suen -
Michael Haupt