On 3 July 2013 20:06, Victor Stinner <victor.stin...@gmail.com> wrote:
> Hi, > > For my registervm project (fork of CPython using register-based > bytecode, instead of stack-based bytecode), I implemented a > Instruction.use_stack() method which just checks if the stack is > "used": read the stack, exchange values in the stack (like "ROT" > instruction), push or pop a value. > > Instruction.use_stack(): > > http://hg.python.org/sandbox/registervm/file/ff24dfecc27d/Lib/registervm.py#l546 > > The method uses a dummy heuristic, just because it was quick to > implement it, and it's enough for my use case. > > To answer your question: yes, I would like a opcode_stack_effect() > function. > > registervm has its own disassembler which creates objects, rather than > just generating a text representation of the bytecode. I'm using > objects because I rewrite most instructions and I need more > information and functions: > > * disassembler (raw bytes => list of instructions) > * assembler (list of instructions => raw bytes) > * format an instruction (human readable assembler) > * is_terminal(): last instruction of a block > * is_cond_jump(): the instruction is a conditional jump? hesitate to > move this disassembler to CPython directly. I'm not sure that it would > be useful, its API is maybe too specific to my registervm project. > * is_reg_used(), is_reg_replaced(), is_reg_modified(), etc.: checks on > registers > * etc. > > Would it be useful to have such high-level API in Python? > I finally committed a longstanding patch to add something like that a while ago for 3.4: http://docs.python.org/dev/library/dis#bytecode-analysis It's still fairly low level, but already far more programmatically useful than the old disassembler text. I'm still inclined to push higher level stuff out to external libraries - this patch was mostly about making some of our compiler tests a bit more maintainable, as well as giving third party libraries better building blocks without changing the dis module too much. To get back to Larry's question, though, I think exposing the stack effects through dis.Instruction would be a good idea (since that will have access to the oparg to calculate the variable effects). As far as how to expose the data to Python goes, I suggest adding an _opcode C module to back opcode.py and eliminate the manual duplication of the opcode values while you're at it. Cheers, Nick. -- Nick Coghlan | ncogh...@gmail.com | Brisbane, Australia
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