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. for block in cfg_ir.get_all_blocks(entry_point):
  115. for definition in block.parameters + block.definitions:
  116. def_dependencies[definition].update(
  117. [dep for dep in definition.get_all_dependencies()
  118. if isinstance(dep, cfg_ir.Definition)])
  119. if definition.has_side_effects():
  120. root_defs.add(definition)
  121. for dep in block.flow.get_dependencies():
  122. if isinstance(dep, cfg_ir.Definition):
  123. root_defs.add(dep)
  124. else:
  125. assert isinstance(dep, cfg_ir.Branch)
  126. for param, arg in zip(dep.block.parameters, dep.arguments):
  127. def_dependencies[param].add(arg)
  128. live_defs = set()
  129. def __mark_live(definition):
  130. if definition in live_defs:
  131. return
  132. live_defs.add(definition)
  133. if definition in def_dependencies:
  134. for dep in def_dependencies[definition]:
  135. __mark_live(dep)
  136. for root in root_defs:
  137. __mark_live(root)
  138. dead_defs = set.difference(set(def_dependencies.keys()), live_defs)
  139. dead_phis = set()
  140. for dead_def in dead_defs:
  141. if isinstance(dead_def.value, cfg_ir.BlockParameter):
  142. dead_phis.add(dead_def)
  143. else:
  144. dead_def.block.remove_definition(dead_def)
  145. erase_parameters(entry_point, dead_phis)
  146. def eliminate_trivial_phis(entry_point):
  147. """Eliminates trivial block parameters, i.e., block parameters which are really
  148. aliases."""
  149. phi_values = defaultdict(set)
  150. all_blocks = list(cfg_ir.get_all_blocks(entry_point))
  151. for block in all_blocks:
  152. for branch in block.flow.branches():
  153. for phi, arg in zip(branch.block.parameters, branch.arguments):
  154. phi_values[phi].add(arg)
  155. replacements = []
  156. for block in all_blocks:
  157. block_parameters = list(block.parameters)
  158. for parameter_def in block_parameters:
  159. trivial_phi_val = cfg_ir.get_trivial_phi_value(
  160. parameter_def, phi_values[parameter_def])
  161. if trivial_phi_val is not None:
  162. replacements.append((parameter_def, trivial_phi_val))
  163. erase_parameters(entry_point, set([parameter_def for parameter_def, _ in replacements]))
  164. for parameter_def, trivial_phi_val in replacements:
  165. block = parameter_def.block
  166. parameter_def.redefine(trivial_phi_val)
  167. block.prepend_definition(parameter_def)
  168. def erase_parameters(entry_point, parameters_to_erase):
  169. """Erases all arguments for the given set of parameters, and then takes out the
  170. parameters themselves."""
  171. for block in cfg_ir.get_all_blocks(entry_point):
  172. for branch in block.flow.branches():
  173. new_arg_list = []
  174. for parameter, arg in zip(branch.block.parameters, branch.arguments):
  175. if parameter not in parameters_to_erase:
  176. new_arg_list.append(arg)
  177. branch.arguments = new_arg_list
  178. for parameter_def in parameters_to_erase:
  179. parameter_def.block.remove_parameter(parameter_def)
  180. def apply_cfg_intrinsic(intrinsic_function, original_definition, named_args):
  181. """Applies the given intrinsic to the given sequence of named arguments."""
  182. kwargs = dict(named_args)
  183. kwargs['original_def'] = original_definition
  184. return intrinsic_function(**kwargs)
  185. def try_redefine_as_direct_call(definition, jit, called_globals):
  186. """Tries to redefine the given indirect call definition as a direct call."""
  187. call = cfg_ir.get_def_value(definition)
  188. if not isinstance(call, cfg_ir.IndirectFunctionCall):
  189. return
  190. target = cfg_ir.get_def_value(call.target)
  191. if isinstance(target, cfg_ir.LoadPointer):
  192. loaded_ptr = cfg_ir.get_def_value(target.pointer)
  193. if isinstance(loaded_ptr, cfg_ir.ResolveGlobal):
  194. resolved_var_name = loaded_ptr.variable.name
  195. called_globals.add(loaded_ptr)
  196. # Try to resolve the callee as an intrinsic.
  197. intrinsic = jit.get_cfg_intrinsic(resolved_var_name)
  198. if intrinsic is not None:
  199. apply_cfg_intrinsic(intrinsic, definition, call.argument_list)
  200. else:
  201. # Otherwise, build a thunk.
  202. thunk_name = jit.jit_thunk_global(resolved_var_name)
  203. definition.redefine(
  204. cfg_ir.DirectFunctionCall(
  205. thunk_name, call.argument_list, cfg_ir.JIT_CALLING_CONVENTION))
  206. called_globals.add(loaded_ptr)
  207. elif isinstance(target, cfg_ir.Literal):
  208. node_id = target.literal
  209. thunk_name = jit.jit_thunk_constant(node_id)
  210. definition.redefine(
  211. cfg_ir.DirectFunctionCall(
  212. thunk_name, call.argument_list, cfg_ir.JIT_CALLING_CONVENTION))
  213. def get_checked_global(definition):
  214. """If the definition is a check that tests if a global does not exist, then
  215. the instruction that resolves the global is returned; otherwise None."""
  216. def_value = cfg_ir.get_def_value(definition)
  217. if not isinstance(def_value, cfg_ir.Binary):
  218. return None
  219. if def_value.operator != 'is':
  220. return None
  221. def __get_checked_global_single_dir(lhs, rhs):
  222. if (isinstance(lhs, cfg_ir.ResolveGlobal)
  223. and isinstance(rhs, cfg_ir.Literal)
  224. and rhs.literal is None):
  225. return lhs
  226. else:
  227. return None
  228. bin_lhs = cfg_ir.get_def_value(def_value.lhs)
  229. bin_rhs = cfg_ir.get_def_value(def_value.rhs)
  230. result = __get_checked_global_single_dir(bin_lhs, bin_rhs)
  231. if result is None:
  232. result = __get_checked_global_single_dir(bin_rhs, bin_lhs)
  233. return result
  234. def optimize_calls(entry_point, jit):
  235. """Converts indirect calls to direct calls in the control-flow graph defined by the
  236. given entry point."""
  237. called_globals = set()
  238. global_exists_defs = defaultdict(list)
  239. all_blocks = list(cfg_ir.get_all_blocks(entry_point))
  240. for block in all_blocks:
  241. for definition in block.definitions:
  242. checked_global = get_checked_global(definition)
  243. if checked_global is not None:
  244. global_exists_defs[checked_global].append(definition)
  245. else:
  246. try_redefine_as_direct_call(definition, jit, called_globals)
  247. for resolve_global in called_globals:
  248. for exists_def in global_exists_defs[resolve_global]:
  249. exists_def.redefine(cfg_ir.Literal(False))
  250. def simplify_values(entry_point):
  251. """Simplifies values in the control-flow graph defined by the given entry point."""
  252. for block in cfg_ir.get_all_blocks(entry_point):
  253. for definition in block.definitions:
  254. def_val = cfg_ir.get_def_value(definition)
  255. if isinstance(def_val, cfg_ir.Read):
  256. read_node = cfg_ir.get_def_value(def_val.node)
  257. if isinstance(read_node, cfg_ir.CreateNode):
  258. definition.redefine(read_node.value)
  259. elif isinstance(def_val, cfg_ir.Binary):
  260. lhs = cfg_ir.get_def_value(def_val.lhs)
  261. rhs = cfg_ir.get_def_value(def_val.rhs)
  262. if isinstance(lhs, cfg_ir.Literal) and isinstance(rhs, cfg_ir.Literal):
  263. definition.redefine(
  264. cfg_ir.Literal(
  265. eval('%r %s %r' % (lhs.literal, def_val.operator, rhs.literal))))
  266. def inline_constants(entry_point):
  267. """Replaces reads of constant nodes by the literals they contain."""
  268. for block in cfg_ir.get_all_blocks(entry_point):
  269. for definition in block.definitions:
  270. def_val = cfg_ir.get_def_value(definition)
  271. if isinstance(def_val, cfg_ir.Read):
  272. read_node = cfg_ir.get_def_value(def_val.node)
  273. if isinstance(read_node, cfg_ir.Literal):
  274. val, = yield [("RV", [read_node.literal])]
  275. definition.redefine(cfg_ir.Literal(val))
  276. def expand_indirect_definitions(entry_point):
  277. """Replaces indirect definitions by the values referred to by those definitions."""
  278. def __expand_indirect_defs(value):
  279. dependencies = value.get_dependencies()
  280. if len(dependencies) == 0:
  281. return value
  282. else:
  283. new_dependencies = []
  284. for dep in dependencies:
  285. new_dep = dep
  286. if isinstance(new_dep, cfg_ir.Definition):
  287. while isinstance(new_dep.value, cfg_ir.Definition):
  288. new_dep = new_dep.value
  289. else:
  290. new_dep = __expand_indirect_defs(new_dep)
  291. new_dependencies.append(new_dep)
  292. return value.create(new_dependencies)
  293. for block in cfg_ir.get_all_blocks(entry_point):
  294. block_definitions = list(block.definitions)
  295. for definition in block_definitions:
  296. if isinstance(definition.value, cfg_ir.Definition):
  297. block.remove_definition(definition)
  298. else:
  299. definition.redefine(
  300. __expand_indirect_defs(definition.value))
  301. block.flow = __expand_indirect_defs(block.flow)
  302. def optimize_reads(entry_point):
  303. """Tries to replace repeated reads by a single read."""
  304. cfg_ir.match_and_rewrite(
  305. entry_point,
  306. lambda _: True,
  307. lambda use_def, _: cfg_ir.is_value_def(use_def, cfg_ir.Read),
  308. lambda def_def:
  309. def_def.redefine(
  310. cfg_ir.Read(def_def.insert_before(def_def.value))),
  311. lambda use_def, def_def: use_def.redefine(def_def))
  312. def optimize(entry_point, jit):
  313. """Optimizes the control-flow graph defined by the given entry point.
  314. A potentially altered entry point is returned."""
  315. optimize_graph_flow(entry_point)
  316. elide_local_checks(entry_point)
  317. optimize_graph_flow(entry_point)
  318. eliminate_trivial_phis(entry_point)
  319. entry_point = cfg_ssa_construction.construct_ssa_form(entry_point)
  320. optimize_calls(entry_point, jit)
  321. cfg_data_structures.optimize_data_structures(entry_point)
  322. yield [("CALL_ARGS", [inline_constants, (entry_point,)])]
  323. optimize_reads(entry_point)
  324. simplify_values(entry_point)
  325. eliminate_unused_definitions(entry_point)
  326. optimize_graph_flow(entry_point)
  327. expand_indirect_definitions(entry_point)
  328. eliminate_unused_definitions(entry_point)
  329. merge_blocks(entry_point)
  330. raise primitive_functions.PrimitiveFinished(entry_point)