1 #!/usr/bin/env python 2 3 """ 4 A really simple virtual processor employing a simple set of instructions which 5 ignore low-level operations and merely concentrate on variable access, structure 6 access, structure allocation and function invocations. 7 8 Copyright (C) 2007, 2008, 2009 Paul Boddie <paul@boddie.org.uk> 9 10 This program is free software; you can redistribute it and/or modify it under 11 the terms of the GNU General Public License as published by the Free Software 12 Foundation; either version 3 of the License, or (at your option) any later 13 version. 14 15 This program is distributed in the hope that it will be useful, but WITHOUT 16 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS 17 FOR A PARTICULAR PURPOSE. See the GNU General Public License for more 18 details. 19 20 You should have received a copy of the GNU General Public License along with 21 this program. If not, see <http://www.gnu.org/licenses/>. 22 23 -------- 24 25 The execution model of the virtual processor involves the following things: 26 27 * Memory contains constants, global variable 28 references and program code 29 30 * PC (program counter) stack contains the return address associated 31 with each function invocation 32 33 * Frame stack contains invocation frames in use and in 34 preparation plus temporary storage 35 36 * Local frame pointer stack refers to the frames in the frame stack 37 38 * Invocation frame pointer stack 39 40 * Exception handler stack 41 42 * Exception handler locals stack refers to the state of the local frame 43 pointer stack 44 45 * Exception handler PC stack refers to the state of the PC stack 46 47 * Registers: current value, 48 boolean status value, 49 source value, 50 current result, 51 current exception, 52 current callable 53 """ 54 55 from micropython.program import DataObject # for creating "nice" new objects 56 57 class IllegalInstruction(Exception): 58 pass 59 60 class IllegalAddress(Exception): 61 def __init__(self, address): 62 self.address = address 63 def __repr__(self): 64 return "IllegalAddress(%r)" % self.address 65 def __str__(self): 66 return repr(self) 67 68 class EmptyPCStack(Exception): 69 pass 70 71 class EmptyFrameStack(Exception): 72 pass 73 74 class BreakpointReached(Exception): 75 pass 76 77 class RSVPMachine: 78 79 "A really simple virtual processor." 80 81 def __init__(self, memory, objlist, paramlist, true_constant, false_constant, pc=None, debug=0): 82 83 """ 84 Initialise the processor with a 'memory' (a list of values containing 85 instructions and data), the object and parameter lists 'objlist' and 86 'paramlist', the addresses 'true_constant' and 'false_constant', and the 87 optional program counter 'pc'. 88 """ 89 90 self.memory = memory 91 self._objlist = objlist 92 self._paramlist = paramlist 93 self.objlist = objlist.as_raw() 94 self.paramlist = paramlist.as_raw() 95 self.true_constant = true_constant 96 self.false_constant = false_constant 97 98 self.pc = pc or 0 99 self.debug = debug 100 101 # Stacks. 102 103 self.pc_stack = [] 104 self.frame_stack = [] 105 self.local_sp_stack = [0] 106 self.invocation_sp_stack = [] 107 self.handler_stack = [len(self.memory) - 1] # final handler is the end of the code 108 self.handler_local_sp_stack = [] 109 self.handler_pc_stack = [] 110 111 # Registers. 112 113 self.instruction = None 114 self.operand = None 115 self.value = None 116 self.status = None 117 self.source = None 118 self.callable = None 119 self.result = None 120 self.exception = None 121 122 # Constants. 123 124 cls = self._get_class("__builtins__", "AttributeError") 125 self.attr_error = cls.location 126 self.attr_error_instance = cls.instance_template_location 127 cls = self._get_class("__builtins__", "TypeError") 128 self.type_error = cls.location 129 self.type_error_instance = cls.instance_template_location 130 cls = self._get_class("__builtins__", "IndexError") 131 self.index_error = cls.location 132 self.index_error_instance = cls.instance_template_location 133 134 # Native class constants. 135 136 cls = self._get_class("__builtins__", "int") 137 self.int_class = cls.location 138 self.int_instance = cls.instance_template_location 139 cls = self._get_class("__builtins__", "list") 140 self.list_instance = cls.instance_template_location 141 142 # Debugging attributes. 143 144 self.breakpoints = set() 145 146 def _get_class(self, module, name): 147 return self._objlist.access(module, name).get_value() 148 149 # Debugging methods. 150 151 def dump(self): 152 print "PC", self.pc, "->", self.load(self.pc) 153 print "PC stack", self.pc_stack 154 print "Frame stack", self.frame_stack 155 print "Local stack pointers", self.local_sp_stack 156 print "Invocation stack pointers", self.invocation_sp_stack 157 print "Handler stack", self.handler_stack 158 print "Handler frame stack", self.handler_local_sp_stack 159 print "Handler PC stack", self.handler_pc_stack 160 print 161 print "Instruction", self.instruction 162 print "Operand", self.operand 163 print "Value", self.value 164 print "Status", self.status 165 print "Source", self.source 166 print "Callable", self.callable 167 print "Result", self.result 168 print "Exception", self.exception 169 170 def show(self): 171 self.show_memory(self.memory, 0) 172 173 def show_pc(self, run_in=10): 174 start = max(0, self.pc - run_in) 175 end = self.pc + run_in 176 memory = self.memory[start:end] 177 self.show_memory(memory, start) 178 179 def show_memory(self, memory, start): 180 for i, x in enumerate(memory): 181 location = start + i 182 if location == self.pc: 183 print "->", 184 else: 185 print " ", 186 print "%5d %r" % (location, x) 187 188 def step(self, dump=0): 189 self.execute() 190 self.show_pc() 191 if dump: 192 self.dump() 193 194 def set_break(self, location): 195 self.breakpoints.add(location) 196 197 # Internal operations. 198 199 def load(self, address): 200 201 "Return the value at the given 'address'." 202 203 try: 204 return self.memory[address] 205 except IndexError: 206 raise IllegalAddress(address) 207 except TypeError: 208 raise IllegalAddress(address) 209 210 def save(self, address, value): 211 212 "Save to the given 'address' the specified 'value'." 213 214 try: 215 self.memory[address] = value 216 except IndexError: 217 raise IllegalAddress(address) 218 except TypeError: 219 raise IllegalAddress(address) 220 221 def new(self, size): 222 223 """ 224 Allocate space of the given 'size', returning the address of the space. 225 """ 226 227 addr = len(self.memory) 228 for i in range(0, size): 229 self.memory.append(None) 230 return addr 231 232 def push_pc(self, data): 233 234 "Push 'data' onto the PC stack." 235 236 self.pc_stack.append(data) 237 238 def pull_pc(self): 239 240 "Pull a value from the PC stack and return it." 241 242 try: 243 return self.pc_stack.pop() 244 except IndexError: 245 raise EmptyPCStack 246 247 def run(self): 248 249 "Execute code in the memory, starting from the current PC address." 250 251 try: 252 while 1: 253 self.execute() 254 except EmptyPCStack: 255 pass 256 257 print "Execution terminated", 258 if self.exception is not None: 259 ref = self.exception 260 addr = self.load(ref + 1) 261 print "with exception:", self.load(ref) 262 print "At address %d: %r" % (addr, self.load(addr)) 263 else: 264 print "successfully." 265 266 def execute(self): 267 268 "Execute code in the memory at the current PC address." 269 270 if self.pc in self.breakpoints: 271 self.breakpoints.remove(self.pc) 272 raise BreakpointReached 273 274 self.instruction = self.load(self.pc) 275 276 # Process any inputs of the instruction. 277 278 self.process_inputs() 279 280 # Perform the instruction itself. 281 282 next_pc = self.perform(self.instruction) 283 284 # Update the program counter. 285 286 if next_pc is None: 287 self.pc += 1 288 else: 289 self.pc = next_pc 290 291 def get_method(self, instruction): 292 293 "Return the handler method for the given 'instruction'." 294 295 instruction_name = instruction.__class__.__name__ 296 if self.debug: 297 print "%8d %s" % (self.pc, instruction_name) 298 method = getattr(self, instruction_name, None) 299 if method is None: 300 raise IllegalInstruction, (self.pc, instruction_name) 301 return method 302 303 def perform(self, instruction): 304 305 "Perform the 'instruction', returning the next PC value or None." 306 307 self.operand = instruction.get_operand() 308 method = self.get_method(instruction) 309 return method() 310 311 def process_inputs(self): 312 313 """ 314 Process any inputs of the current instruction. This permits any directly 315 connected sub-instructions to produce the effects that separate 316 instructions would otherwise have. 317 """ 318 319 value = self.value 320 if self.instruction.source is not None: 321 self.perform(self.instruction.source) 322 self.source = self.value 323 self.value = value 324 if self.instruction.input is not None: 325 self.perform(self.instruction.input) 326 327 def jump(self, addr, next): 328 329 """ 330 Jump to the subroutine at (or identified by) 'addr'. If 'addr' 331 identifies a library function then invoke the library function and set 332 PC to 'next' afterwards; otherwise, set PC to 'addr'. 333 """ 334 335 # Trap library functions introduced through the use of strings instead 336 # of proper locations. 337 338 if isinstance(addr, str): 339 handler = self.native_functions[addr](self) 340 if handler is None: 341 return next 342 else: 343 return handler 344 else: 345 self.push_pc(self.pc + 1) 346 return addr 347 348 # Instructions. 349 350 def LoadConst(self): 351 self.value = self.operand, self.operand 352 353 def LoadFunction(self): 354 self.value = None, self.operand # context of constant is not interesting 355 356 def LoadName(self): 357 frame = self.local_sp_stack[-1] 358 self.value = self.frame_stack[frame + self.operand] 359 360 def StoreName(self): 361 frame = self.local_sp_stack[-1] 362 self.frame_stack[frame + self.operand] = self.source 363 364 LoadTemp = LoadName 365 366 def StoreTemp(self): 367 frame = self.local_sp_stack[-1] 368 self.frame_stack[frame + self.operand] = self.value 369 370 def LoadAddress(self): 371 # Preserve context (potentially null). 372 self.value = self.load(self.operand) 373 374 def LoadAddressContext(self): 375 context, ref = self.load(self.operand) 376 inst_context, inst_ref = self.value 377 self.value = inst_ref, ref 378 379 def LoadAddressContextCond(self): 380 context, ref = self.load(self.operand) 381 inst_context, inst_ref = self.value 382 self.value = self._LoadAddressContextCond(context, ref, inst_ref) 383 384 def StoreAddress(self): 385 # Preserve context. 386 self.save(self.operand, self.source) 387 388 def StoreAddressContext(self): 389 # Overwrite context if null. 390 context_context, context_ref = self.value 391 source_context, source_ref = self.source 392 if source_context is None: 393 context = context_ref 394 else: 395 context = source_context 396 self.save(self.operand, (context, source_ref)) 397 398 def MakeObject(self): 399 size = self.operand 400 context, ref = self.value 401 # NOTE: Referencing the instance template. 402 addr = self._MakeObject(size, ref - 1) 403 # Introduce object as context for the new object. 404 self.value = addr, addr 405 406 def LoadAttr(self): 407 context, ref = self.value 408 # Retrieved context should already be appropriate for the instance. 409 # NOTE: Adding 1 to skip any header. 410 self.value = self.load(ref + self.operand + 1) 411 412 def StoreAttr(self): 413 context, ref = self.value 414 # Target should already be an instance. 415 # NOTE: Adding 1 to skip any header. 416 self.save(ref + self.operand + 1, self.source) 417 418 def LoadAttrIndex(self): 419 context, ref = self.value 420 data = self.load(ref) 421 element = self.objlist[data.classcode + self.operand] 422 attr_index, class_attr, offset = element 423 if attr_index == self.operand: 424 if class_attr: 425 self.value = self.load(offset) # offset is address of class attribute 426 else: 427 self.value = self.load(ref + offset) 428 else: 429 self.exception = self._MakeObject(2, self.attr_error_instance) 430 return self.RaiseException() 431 432 # LoadAttrIndexContext not defined. 433 434 def LoadAttrIndexContextCond(self): 435 context, ref = self.value 436 data = self.load(ref) 437 element = self.objlist[data.classcode + self.operand] 438 attr_index, class_attr, offset = element 439 if attr_index == self.operand: 440 if class_attr: 441 loaded_context, loaded_ref = self.load(offset) # offset is address of class attribute 442 if data.attrcode is None: # absent attrcode == class 443 self.value = loaded_context, loaded_ref 444 else: 445 self.value = self._LoadAddressContextCond(loaded_context, loaded_ref, ref) 446 else: 447 self.value = self.load(ref + offset) 448 else: 449 self.exception = self._MakeObject(2, self.attr_error_instance) 450 return self.RaiseException() 451 452 def StoreAttrIndex(self): 453 context, ref = self.value 454 data = self.load(ref) 455 element = self.objlist[data.classcode + self.operand] 456 attr_index, class_attr, offset = element 457 if attr_index == self.operand: 458 if class_attr: 459 self.exception = self._MakeObject(2, self.type_error_instance) 460 return self.RaiseException() 461 else: 462 self.save(ref + offset, self.source) 463 else: 464 self.exception = self._MakeObject(2, self.attr_error_instance) 465 return self.RaiseException() 466 467 # NOTE: LoadAttrIndexContext is a possibility if a particular attribute can always be overridden. 468 469 def MakeFrame(self): 470 self.invocation_sp_stack.append(len(self.frame_stack)) 471 self.frame_stack.extend([None] * self.operand) 472 473 def DropFrame(self): 474 self.local_sp_stack.pop() 475 frame = self.invocation_sp_stack.pop() 476 self.frame_stack = self.frame_stack[:frame] # reset stack before call 477 478 def RecoverFrame(self): 479 self.local_sp_stack.pop() 480 481 def StoreFrame(self): 482 frame = self.invocation_sp_stack[-1] # different from the current frame after MakeFrame 483 self.frame_stack[frame + self.operand] = self.value 484 485 def StoreFrameIndex(self): 486 context, ref = self.value 487 frame = self.invocation_sp_stack[-1] # different from the current frame after MakeFrame 488 data = self.load(ref) 489 element = self.paramlist[data.funccode + self.operand] 490 # NOTE: Need to ensure correct positioning where a context has been generated. 491 param_index, offset = element 492 if param_index == self.operand: 493 self.frame_stack[frame + offset + 1] = self.source # add 1 to skip the context always generated 494 else: 495 self.exception = self._MakeObject(2, self.type_error_instance) 496 return self.RaiseException() 497 498 def LoadCallable(self): 499 context, ref = self.value 500 data = self.load(ref) 501 self.callable = data.codeaddr 502 503 def StoreCallable(self): 504 context, ref = self.value 505 # NOTE: Should improve the representation and permit direct saving. 506 data = self.load(ref) 507 self.save(ref, (data.classcode, data.attrcode) + self.callable) 508 509 def LoadContext(self): 510 context, ref = self.value 511 # NOTE: Omission of the context of the context would make things like 512 # NOTE: self() inside methods impossible. 513 self.value = context, context 514 515 def CheckContext(self): 516 self.status = self.value[1] is not None 517 518 def CheckClassContext(self): 519 context_context, context_ref = self.value 520 context_data = self.load(context_ref) 521 522 # Classes are not themselves usable as the self argument. 523 # NOTE: This may change at some point. 524 # However, where classes appear as the context, instance 525 # compatibility is required in the first argument. 526 527 self.status = context_data.attrcode is None # absent attrcode == class 528 529 def CheckFrame(self): 530 (nargs, ndefaults, has_star) = self.operand 531 532 # The frame is actually installed as the locals. 533 # Retrieve the context from the first local. 534 535 frame = self.local_sp_stack[-1] 536 nlocals = len(self.frame_stack[frame:]) 537 538 if not ((nargs - ndefaults) <= nlocals and (nlocals <= nargs or has_star)): 539 #raise Exception, "CheckFrame %r (%r <= %r <= %r)" % (self.operand, nargs - ndefaults, nlocals, nargs) 540 self.exception = self._MakeObject(2, self.type_error_instance) 541 return self.RaiseException() 542 543 def FillDefaults(self): 544 # NOTE: Make the get_operand method of the instruction provide the 545 # NOTE: function location. 546 (nargs, ndefaults, fn) = self.operand 547 548 # The frame is actually installed as the locals. 549 550 frame = self.local_sp_stack[-1] 551 nlocals = len(self.frame_stack[frame:]) 552 553 # Support population of defaults. 554 # This involves copying the "attributes" of a function into the frame. 555 556 default = nlocals - (nargs - ndefaults) 557 self.frame_stack.extend([None] * (nargs - nlocals)) 558 pos = nlocals 559 ref = fn.location 560 561 while pos < nargs: 562 self.frame_stack[frame + pos] = self.load(ref + default + 1) # skip header 563 default += 1 564 pos += 1 565 566 def CheckSelf(self): 567 context, ref = self.value 568 target_context, target_ref = self.source 569 570 # Check the details of the proposed context and the target's context. 571 572 self.status = self._CheckInstance(ref, target_context) 573 574 def JumpWithFrame(self): 575 codeaddr = self.callable 576 self.local_sp_stack.append(self.invocation_sp_stack[-1]) # adopt the invocation frame 577 return self.jump(codeaddr, self.pc + 1) # return to the instruction after this one 578 579 def JumpWithFrameDirect(self): 580 operand = self.operand 581 self.local_sp_stack.append(self.invocation_sp_stack[-1]) # adopt the invocation frame 582 return self.jump(operand, self.pc + 1) # return to the instruction after this one 583 584 def ExtendFrame(self): 585 self.frame_stack.extend([None] * self.operand) 586 587 def AdjustFrame(self): 588 self.invocation_sp_stack[-1] += self.operand 589 590 def Return(self): 591 return self.pull_pc() 592 593 def LoadResult(self): 594 self.value = self.result 595 596 def StoreResult(self): 597 self.result = self.value 598 599 def Jump(self): 600 return self.operand 601 602 def JumpIfTrue(self): 603 if self.status: 604 return self.operand 605 606 def JumpIfFalse(self): 607 if not self.status: 608 return self.operand 609 610 def LoadException(self): 611 self.value = self.exception, self.exception 612 613 def StoreException(self): 614 self.exception = self.value[1] 615 616 def RaiseException(self): 617 # NOTE: Adding the program counter as the first attribute. 618 self.save(self.exception + 1, self.pc) 619 # Jumping to the current handler. 620 return self.handler_stack[-1] 621 622 def PushHandler(self): 623 self.handler_stack.append(self.operand) 624 self.handler_local_sp_stack.append(len(self.local_sp_stack)) 625 self.handler_pc_stack.append(len(self.pc_stack)) 626 627 def PopHandler(self): 628 # Reduce the local frame pointer stack to refer to the handler's frame. 629 self.local_sp_stack = self.local_sp_stack[:self.handler_local_sp_stack.pop()] 630 # Reduce the PC stack to discard all superfluous return addresses. 631 self.pc_stack = self.pc_stack[:self.handler_pc_stack.pop()] 632 self.handler_stack.pop() 633 634 def CheckException(self): 635 self.status = self.exception is not None and self._CheckInstance(self.exception, self.value[1]) 636 637 def TestIdentity(self): 638 self.status = self.value[1] == self.source[1] 639 640 def TestIdentityAddress(self): 641 self.status = self.value[1] == self.operand 642 643 # LoadBoolean is implemented in the generated code. 644 # StoreBoolean is implemented by testing against the True value. 645 646 def InvertBoolean(self): 647 self.status = not self.status 648 649 # Common implementation details. 650 651 def _CheckInstance(self, ref, cls): 652 data = self.load(ref) 653 target_data = self.load(cls) 654 655 # Insist on instance vs. class. 656 657 if data.attrcode is None: # absent attrcode == class 658 return 0 659 660 if target_data.attrcode is not None: # present attrcode == instance 661 return 0 662 663 # Find the table entry for the descendant. 664 665 element = self.objlist[target_data.classcode + data.attrcode] 666 if element is not None: 667 attr_index, class_attr, offset = element 668 return attr_index == data.attrcode 669 else: 670 return 0 671 672 def _MakeObject(self, size, ref): 673 # Load the template. 674 data = self.load(ref) 675 addr = self.new(size) 676 # Save the header, overriding the size. 677 self.save(addr, data.with_size(size)) 678 return addr 679 680 def _LoadAddressContextCond(self, context, ref, inst_ref): 681 682 # Check the instance context against the target's context. 683 684 if self._CheckInstance(inst_ref, context): 685 # Replace the context with the instance. 686 return inst_ref, ref 687 else: 688 return context, ref 689 690 # Native function implementations. 691 692 def builtins_int_add(self): 693 frame = self.local_sp_stack[-1] 694 695 # Get operands addresses. 696 697 left_context, left = self.frame_stack[frame] 698 right_context, right = self.frame_stack[frame + 1] 699 700 # Test operand suitability. 701 702 if not self._CheckInstance(left, self.int_class) and self._CheckInstance(right, self.int_class): 703 self.exception = self._MakeObject(2, self.type_error_instance) 704 return self.RaiseException() 705 706 # NOTE: Assume single location for data. 707 708 left_data = left + 1 709 right_data = right + 1 710 711 # Make a new object. 712 713 addr = self._MakeObject(2, self.int_instance) 714 715 # Store the result. 716 # NOTE: The data is considered ready to use. 717 718 self.save(addr + 1, self.load(left_data) + self.load(right_data)) 719 720 # Return the new object. 721 # Introduce object as context for the new object. 722 723 self.result = addr, addr 724 725 def builtins_int_bool(self): 726 frame = self.local_sp_stack[-1] 727 728 # Get operands addresses. 729 730 left_context, left = self.frame_stack[frame] 731 732 # Test operand suitability. 733 734 if not self._CheckInstance(left, self.int_class): 735 self.exception = self._MakeObject(2, self.type_error_instance) 736 return self.RaiseException() 737 738 # NOTE: Assume single location for data. 739 740 left_data = left + 1 741 742 # Test the data. 743 # NOTE: The data is considered ready to use. 744 745 if self.load(left_data) != 0: 746 self.result = self.true_constant, self.true_constant 747 else: 748 self.result = self.false_constant, self.false_constant 749 750 def builtins_int_neg(self): 751 frame = self.local_sp_stack[-1] 752 753 # Get operands addresses. 754 755 left_context, left = self.frame_stack[frame] 756 757 # Test operand suitability. 758 759 if not self._CheckInstance(left, self.int_class): 760 self.exception = self._MakeObject(2, self.type_error_instance) 761 return self.RaiseException() 762 763 # NOTE: Assume single location for data. 764 765 left_data = left + 1 766 767 # Make a new object. 768 769 addr = self._MakeObject(2, self.int_instance) 770 771 # Store the result. 772 # NOTE: The data is considered ready to use. 773 774 self.save(addr + 1, -self.load(left_data)) 775 776 # Return the new object. 777 # Introduce object as context for the new object. 778 779 self.result = addr, addr 780 781 def builtins_bool_bool(self): 782 frame = self.local_sp_stack[-1] 783 784 # Get operands addresses. 785 786 left_context, left = self.frame_stack[frame] 787 self.result = left, left 788 789 def builtins_list_new(self): 790 frame = self.local_sp_stack[-1] 791 792 # NOTE: Specific copying of tuples/lists. 793 794 args_context, args = self.frame_stack[frame] 795 header = self.load(args) 796 797 list = self._MakeObject(header.size, self.list_instance) 798 for i in range(1, header.size): 799 self.save(list + i, self.load(args + i)) 800 801 self.result = list, list 802 803 def builtins_list_getitem(self): 804 frame = self.local_sp_stack[-1] 805 806 # Get operands addresses. 807 808 obj_context, obj = self.frame_stack[frame] 809 item_context, item = self.frame_stack[frame + 1] 810 811 header = self.load(obj) 812 nelements = header.size - 1 813 814 # NOTE: Assume single location for data. 815 816 item_pos = self.load(item + 1) 817 if item_pos >= 0 and item_pos < nelements: 818 pass 819 elif item_pos < 0 and item_pos >= -nelements: 820 item_pos = nelements + item_pos 821 else: 822 self.exception = self._MakeObject(2, self.index_error_instance) 823 return self.RaiseException() 824 825 self.result = self.load(obj + 1 + item_pos) 826 827 def builtins_object_init(self): 828 pass 829 830 native_functions = { 831 "__builtins__.int.__add__" : builtins_int_add, 832 "__builtins__.int.__bool__" : builtins_int_bool, 833 "__builtins__.int.__neg__" : builtins_int_neg, 834 "__builtins__.bool.__bool__" : builtins_bool_bool, 835 "__builtins__.list" : builtins_list_new, 836 "__builtins__.list.__getitem__" : builtins_list_getitem, 837 "__builtins__.object.__init__" : builtins_object_init, 838 } 839 840 # 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