cfg_optimization.py 16 KB

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  1. """Optimizes and analyzes CFG-IR."""
  2. from collections import defaultdict
  3. import modelverse_jit.cfg_ir as cfg_ir
  4. import modelverse_jit.cfg_dominators as cfg_dominators
  5. import modelverse_jit.cfg_ssa_construction as cfg_ssa_construction
  6. import modelverse_jit.cfg_data_structures as cfg_data_structures
  7. import modelverse_kernel.primitives as primitive_functions
  8. def is_empty_block(block):
  9. """Tests if the given block contains no parameters or definitions."""
  10. return len(block.parameters) == 0 and len(block.definitions) == 0
  11. def optimize_flow(block):
  12. """Optimizes the given block's flow instruction."""
  13. changed = True
  14. while changed:
  15. changed = False
  16. # Select flow with a literal condition can be optimized to a direct jump.
  17. if (isinstance(block.flow, cfg_ir.SelectFlow)
  18. and cfg_ir.is_literal_def(block.flow.condition)):
  19. literal = cfg_ir.get_literal_def_value(block.flow.condition)
  20. block.flow = cfg_ir.JumpFlow(
  21. block.flow.if_branch if literal else block.flow.else_branch)
  22. changed = True
  23. # Jumps to blocks which contain no parameters or definitions can be replaced
  24. # by the target block's flow.
  25. if (isinstance(block.flow, cfg_ir.JumpFlow)
  26. and is_empty_block(block.flow.branch.block)
  27. and block.flow.branch.block is not block):
  28. block.flow = block.flow.branch.block.flow
  29. changed = True
  30. # Branches to blocks which contain nothing but a jump can be replaced by branches
  31. # to the jump's target.
  32. for branch in block.flow.branches():
  33. if (is_empty_block(branch.block)
  34. and branch.block is not block
  35. and isinstance(branch.block.flow, cfg_ir.JumpFlow)):
  36. new_branch = branch.block.flow.branch
  37. branch.block = new_branch.block
  38. branch.arguments = new_branch.arguments
  39. changed = True
  40. def optimize_graph_flow(entry_point):
  41. """Optimizes all flow instructions in the graph defined by the given entry point."""
  42. for block in cfg_ir.get_all_blocks(entry_point):
  43. optimize_flow(block)
  44. def merge_blocks(entry_point):
  45. """Merges blocks which have exactly one predecessor with said predecessor, if the
  46. predecessor has a jump flow instruction."""
  47. predecessor_map = cfg_ir.get_all_predecessor_blocks(entry_point)
  48. queue = set(predecessor_map.keys())
  49. queue.add(entry_point)
  50. def __do_merge(source, target):
  51. target_params = list(target.parameters)
  52. branch_args = list(source.flow.branch.arguments)
  53. for target_param, branch_arg in zip(target_params, branch_args):
  54. target.remove_parameter(target_param)
  55. target_param.redefine(branch_arg)
  56. source.append_definition(target_param)
  57. target_defs = list(target.definitions)
  58. for target_def in target_defs:
  59. target.remove_definition(target_def)
  60. source.append_definition(target_def)
  61. source.flow = target.flow
  62. for pred_set in predecessor_map.values():
  63. if target in pred_set:
  64. pred_set.remove(target)
  65. pred_set.add(source)
  66. while len(queue) > 0:
  67. block = queue.pop()
  68. if isinstance(block.flow, cfg_ir.JumpFlow):
  69. next_block = block.flow.branch.block
  70. preds = predecessor_map[next_block]
  71. if (len(preds) == 1
  72. and next(iter(preds)) == block
  73. and block != next_block
  74. and next_block != entry_point):
  75. __do_merge(block, next_block)
  76. del predecessor_map[next_block]
  77. queue.add(block)
  78. if next_block in queue:
  79. queue.remove(next_block)
  80. def elide_local_checks(entry_point):
  81. """Tries to elide redundant checks on local variables."""
  82. # The plan here is to replace all check-local-exists defs by literals if
  83. # they are either dominated by an appropriate declare-local or not reachable
  84. # from a declare-local.
  85. local_checks = defaultdict(set)
  86. local_defs = defaultdict(set)
  87. for block in cfg_ir.get_all_blocks(entry_point):
  88. for definition in block.definitions:
  89. if cfg_ir.is_value_def(definition, cfg_ir.CheckLocalExists):
  90. local_checks[cfg_ir.get_def_variable(definition).node_id].add(definition)
  91. elif cfg_ir.is_value_def(definition, cfg_ir.DeclareLocal):
  92. local_defs[cfg_ir.get_def_variable(definition).node_id].add(definition)
  93. dominator_tree = cfg_dominators.get_dominator_tree(entry_point)
  94. reachable_blocks = cfg_ir.get_all_reachable_blocks(entry_point)
  95. for (variable, all_checks) in local_checks.items():
  96. for check in all_checks:
  97. is_reachable = False
  98. for local_def in local_defs[variable]:
  99. if dominator_tree.dominates_instruction(local_def, check):
  100. # Check is dominated by a definition. Replace it by a 'True' literal.
  101. check.redefine(cfg_ir.Literal(True))
  102. is_reachable = True
  103. break
  104. elif check.block in reachable_blocks[local_def.block]:
  105. is_reachable = True
  106. if not is_reachable:
  107. # Check cannot be reached from any definition. Replace it by a 'False' literal.
  108. check.redefine(cfg_ir.Literal(False))
  109. def eliminate_unused_definitions(entry_point):
  110. """Tries to eliminate unused definitions in the control-flow graphb defined by the
  111. given entry point."""
  112. def_dependencies = defaultdict(set)
  113. root_defs = set()
  114. # Gather dependencies.
  115. for block in cfg_ir.get_all_blocks(entry_point):
  116. for definition in block.parameters + block.definitions:
  117. all_dependencies = list(definition.get_all_dependencies())
  118. def_dependencies[definition].update(
  119. [dep for dep in all_dependencies
  120. if isinstance(dep, cfg_ir.Definition)])
  121. if len(all_dependencies) > 0 and definition.has_bidirectional_dependencies():
  122. for dep in all_dependencies:
  123. def_dependencies[dep].add(definition)
  124. if definition.has_side_effects():
  125. root_defs.add(definition)
  126. for dep in block.flow.get_dependencies():
  127. if isinstance(dep, cfg_ir.Definition):
  128. root_defs.add(dep)
  129. else:
  130. assert isinstance(dep, cfg_ir.Branch)
  131. for param, arg in zip(dep.block.parameters, dep.arguments):
  132. def_dependencies[param].add(arg)
  133. # Figure out which definitions are live.
  134. live_defs = set()
  135. def __mark_live(definition):
  136. if definition in live_defs:
  137. return
  138. live_defs.add(definition)
  139. if definition in def_dependencies:
  140. for dep in def_dependencies[definition]:
  141. __mark_live(dep)
  142. for root in root_defs:
  143. __mark_live(root)
  144. # Remove all dead definitions.
  145. dead_defs = set.difference(set(def_dependencies.keys()), live_defs)
  146. dead_phis = set()
  147. for dead_def in dead_defs:
  148. if isinstance(dead_def.value, cfg_ir.BlockParameter):
  149. dead_phis.add(dead_def)
  150. else:
  151. dead_def.block.remove_definition(dead_def)
  152. erase_parameters(entry_point, dead_phis)
  153. def eliminate_trivial_phis(entry_point):
  154. """Eliminates trivial block parameters, i.e., block parameters which are really
  155. aliases."""
  156. phi_values = defaultdict(set)
  157. all_blocks = list(cfg_ir.get_all_blocks(entry_point))
  158. for block in all_blocks:
  159. for branch in block.flow.branches():
  160. for phi, arg in zip(branch.block.parameters, branch.arguments):
  161. phi_values[phi].add(arg)
  162. replacements = []
  163. for block in all_blocks:
  164. block_parameters = list(block.parameters)
  165. for parameter_def in block_parameters:
  166. trivial_phi_val = cfg_ir.get_trivial_phi_value(
  167. parameter_def, phi_values[parameter_def])
  168. if trivial_phi_val is not None:
  169. replacements.append((parameter_def, trivial_phi_val))
  170. erase_parameters(entry_point, set([parameter_def for parameter_def, _ in replacements]))
  171. for parameter_def, trivial_phi_val in replacements:
  172. block = parameter_def.block
  173. parameter_def.redefine(trivial_phi_val)
  174. block.prepend_definition(parameter_def)
  175. def erase_parameters(entry_point, parameters_to_erase):
  176. """Erases all arguments for the given set of parameters, and then takes out the
  177. parameters themselves."""
  178. for block in cfg_ir.get_all_blocks(entry_point):
  179. for branch in block.flow.branches():
  180. new_arg_list = []
  181. for parameter, arg in zip(branch.block.parameters, branch.arguments):
  182. if parameter not in parameters_to_erase:
  183. new_arg_list.append(arg)
  184. branch.arguments = new_arg_list
  185. for parameter_def in parameters_to_erase:
  186. parameter_def.block.remove_parameter(parameter_def)
  187. def apply_cfg_intrinsic(intrinsic_function, original_definition, named_args):
  188. """Applies the given intrinsic to the given sequence of named arguments."""
  189. kwargs = dict(named_args)
  190. kwargs['original_def'] = original_definition
  191. return intrinsic_function(**kwargs)
  192. def try_redefine_as_direct_call(definition, jit, called_globals):
  193. """Tries to redefine the given indirect call definition as a direct call."""
  194. call = cfg_ir.get_def_value(definition)
  195. if not isinstance(call, cfg_ir.IndirectFunctionCall):
  196. return
  197. target = cfg_ir.get_def_value(call.target)
  198. if isinstance(target, cfg_ir.LoadPointer):
  199. loaded_ptr = cfg_ir.get_def_value(target.pointer)
  200. if isinstance(loaded_ptr, cfg_ir.ResolveGlobal):
  201. resolved_var_name = loaded_ptr.variable.name
  202. called_globals.add(loaded_ptr)
  203. # Try to resolve the callee as an intrinsic.
  204. intrinsic = jit.get_cfg_intrinsic(resolved_var_name)
  205. if intrinsic is not None:
  206. apply_cfg_intrinsic(intrinsic, definition, call.argument_list)
  207. else:
  208. # Otherwise, build a thunk.
  209. thunk_name = jit.jit_thunk_global(resolved_var_name)
  210. definition.redefine(
  211. cfg_ir.DirectFunctionCall(
  212. thunk_name, call.argument_list, cfg_ir.JIT_CALLING_CONVENTION))
  213. called_globals.add(loaded_ptr)
  214. elif isinstance(target, cfg_ir.Literal):
  215. node_id = target.literal
  216. thunk_name = jit.jit_thunk_constant(node_id)
  217. definition.redefine(
  218. cfg_ir.DirectFunctionCall(
  219. thunk_name, call.argument_list, cfg_ir.JIT_CALLING_CONVENTION))
  220. def get_checked_global(definition):
  221. """If the definition is a check that tests if a global does not exist, then
  222. the instruction that resolves the global is returned; otherwise None."""
  223. def_value = cfg_ir.get_def_value(definition)
  224. if not isinstance(def_value, cfg_ir.Binary):
  225. return None
  226. if def_value.operator != 'is':
  227. return None
  228. def __get_checked_global_single_dir(lhs, rhs):
  229. if (isinstance(lhs, cfg_ir.ResolveGlobal)
  230. and isinstance(rhs, cfg_ir.Literal)
  231. and rhs.literal is None):
  232. return lhs
  233. else:
  234. return None
  235. bin_lhs = cfg_ir.get_def_value(def_value.lhs)
  236. bin_rhs = cfg_ir.get_def_value(def_value.rhs)
  237. result = __get_checked_global_single_dir(bin_lhs, bin_rhs)
  238. if result is None:
  239. result = __get_checked_global_single_dir(bin_rhs, bin_lhs)
  240. return result
  241. def optimize_calls(entry_point, jit):
  242. """Converts indirect calls to direct calls in the control-flow graph defined by the
  243. given entry point."""
  244. called_globals = set()
  245. global_exists_defs = defaultdict(list)
  246. all_blocks = list(cfg_ir.get_all_blocks(entry_point))
  247. for block in all_blocks:
  248. for definition in block.definitions:
  249. checked_global = get_checked_global(definition)
  250. if checked_global is not None:
  251. global_exists_defs[checked_global].append(definition)
  252. else:
  253. try_redefine_as_direct_call(definition, jit, called_globals)
  254. for resolve_global in called_globals:
  255. for exists_def in global_exists_defs[resolve_global]:
  256. exists_def.redefine(cfg_ir.Literal(False))
  257. def simplify_values(entry_point):
  258. """Simplifies values in the control-flow graph defined by the given entry point."""
  259. for block in cfg_ir.get_all_blocks(entry_point):
  260. for definition in block.definitions:
  261. def_val = cfg_ir.get_def_value(definition)
  262. if isinstance(def_val, cfg_ir.Read):
  263. read_node = cfg_ir.get_def_value(def_val.node)
  264. if isinstance(read_node, cfg_ir.CreateNode):
  265. definition.redefine(read_node.value)
  266. elif isinstance(def_val, cfg_ir.Binary):
  267. lhs = cfg_ir.get_def_value(def_val.lhs)
  268. rhs = cfg_ir.get_def_value(def_val.rhs)
  269. if isinstance(lhs, cfg_ir.Literal) and isinstance(rhs, cfg_ir.Literal):
  270. definition.redefine(
  271. cfg_ir.Literal(
  272. eval('%r %s %r' % (lhs.literal, def_val.operator, rhs.literal))))
  273. def inline_constants(entry_point):
  274. """Replaces reads of constant nodes by the literals they contain."""
  275. for block in cfg_ir.get_all_blocks(entry_point):
  276. for definition in block.definitions:
  277. def_val = cfg_ir.get_def_value(definition)
  278. if isinstance(def_val, cfg_ir.Read):
  279. read_node = cfg_ir.get_def_value(def_val.node)
  280. if isinstance(read_node, cfg_ir.Literal):
  281. val, = yield [("RV", [read_node.literal])]
  282. definition.redefine(cfg_ir.Literal(val))
  283. def expand_indirect_definitions(entry_point):
  284. """Replaces indirect definitions by the values referred to by those definitions."""
  285. def __expand_indirect_defs(value):
  286. dependencies = value.get_dependencies()
  287. if len(dependencies) == 0:
  288. return value
  289. else:
  290. new_dependencies = []
  291. for dep in dependencies:
  292. new_dep = dep
  293. if isinstance(new_dep, cfg_ir.Definition):
  294. while isinstance(new_dep.value, cfg_ir.Definition):
  295. new_dep = new_dep.value
  296. else:
  297. new_dep = __expand_indirect_defs(new_dep)
  298. new_dependencies.append(new_dep)
  299. return value.create(new_dependencies)
  300. for block in cfg_ir.get_all_blocks(entry_point):
  301. block_definitions = list(block.definitions)
  302. for definition in block_definitions:
  303. if isinstance(definition.value, cfg_ir.Definition):
  304. block.remove_definition(definition)
  305. else:
  306. definition.redefine(
  307. __expand_indirect_defs(definition.value))
  308. block.flow = __expand_indirect_defs(block.flow)
  309. def optimize_reads(entry_point):
  310. """Tries to replace repeated reads by a single read."""
  311. cfg_ir.match_and_rewrite(
  312. entry_point,
  313. lambda _: True,
  314. lambda use_def, _: cfg_ir.is_value_def(use_def, cfg_ir.Read),
  315. lambda def_def:
  316. def_def.redefine(
  317. cfg_ir.Read(def_def.insert_before(def_def.value))),
  318. lambda use_def, def_def: use_def.redefine(def_def))
  319. def optimize(entry_point, jit):
  320. """Optimizes the control-flow graph defined by the given entry point.
  321. A potentially altered entry point is returned."""
  322. optimize_graph_flow(entry_point)
  323. elide_local_checks(entry_point)
  324. optimize_graph_flow(entry_point)
  325. eliminate_trivial_phis(entry_point)
  326. entry_point = cfg_ssa_construction.construct_ssa_form(entry_point)
  327. optimize_calls(entry_point, jit)
  328. cfg_data_structures.optimize_data_structures(entry_point)
  329. yield [("CALL_ARGS", [inline_constants, (entry_point,)])]
  330. optimize_reads(entry_point)
  331. simplify_values(entry_point)
  332. eliminate_unused_definitions(entry_point)
  333. optimize_graph_flow(entry_point)
  334. expand_indirect_definitions(entry_point)
  335. eliminate_unused_definitions(entry_point)
  336. merge_blocks(entry_point)
  337. raise primitive_functions.PrimitiveFinished(entry_point)