def _get_pair_first_container(func_ir, rhs): assert isinstance(rhs, ir.Expr) and rhs.op == 'pair_first' iternext = get_definition(func_ir, rhs.value) require(isinstance(iternext, ir.Expr) and iternext.op == 'iternext') getiter = get_definition(func_ir, iternext.value) require(isinstance(iternext, ir.Expr) and getiter.op == 'getiter') return getiter.value
def check(func, arg_tys, bit_val): func_ir = compile_to_ir(func) # check there is 1 branch before_branches = self.find_branches(func_ir) self.assertEqual(len(before_branches), 1) # check the condition in the branch is a binop pred_var = before_branches[0].cond pred_defn = ir_utils.get_definition(func_ir, pred_var) self.assertEqual(pred_defn.op, 'call') condition_var = pred_defn.args[0] condition_op = ir_utils.get_definition(func_ir, condition_var) self.assertEqual(condition_op.op, 'binop') # do the prune, this should kill the dead branch and rewrite the #'condition to a true/false const bit if self._DEBUG: print("=" * 80) print("before prune") func_ir.dump() dead_branch_prune(func_ir, arg_tys) if self._DEBUG: print("=" * 80) print("after prune") func_ir.dump() # after mutation, the condition should be a const value `bit_val` new_condition_defn = ir_utils.get_definition( func_ir, condition_var) self.assertTrue(isinstance(new_condition_defn, ir.Const)) self.assertEqual(new_condition_defn.value, bit_val)
def is_const_slice(typemap, func_ir, var, accept_stride=False): """ return True if var can be determined to be a constant size slice """ require(typemap[var.name] == types.slice2_type or (accept_stride and typemap[var.name] == types.slice3_type)) call_expr = get_definition(func_ir, var) require(isinstance(call_expr, ir.Expr) and call_expr.op == 'call') assert (len(call_expr.args) == 2 or (accept_stride and len(call_expr.args) == 3)) assert find_callname(func_ir, call_expr) == ('slice', 'builtins') arg0_def = get_definition(func_ir, call_expr.args[0]) require(isinstance(arg0_def, ir.Const) and arg0_def.value is None) size_const = find_const(func_ir, call_expr.args[1]) require(isinstance(size_const, int)) return True
def find_build_tuple(func_ir, var): """Check if a variable is constructed via build_tuple and return the sequence or raise GuardException otherwise. """ # variable or variable name require(isinstance(var, (ir.Var, str))) var_def = get_definition(func_ir, var) require(isinstance(var_def, ir.Expr)) require(var_def.op == 'build_tuple') return var_def.items
def find_str_const(func_ir, var): """Check if a variable can be inferred as a string constant, and return the constant value, or raise GuardException otherwise. """ require(isinstance(var, ir.Var)) var_def = get_definition(func_ir, var) if isinstance(var_def, ir.Const): val = var_def.value require(isinstance(val, str)) return val # only add supported (s1+s2), TODO: extend to other expressions require(isinstance(var_def, ir.Expr) and var_def.op == 'binop' and var_def.fn == operator.add) arg1 = find_str_const(func_ir, var_def.lhs) arg2 = find_str_const(func_ir, var_def.rhs) return arg1 + arg2
def _get_const_index_expr_inner(stencil_ir, func_ir, index_var): """inner constant inference function that calls constant, unary and binary cases. """ require(isinstance(index_var, ir.Var)) # case where the index is a const itself in outer function var_const = guard(_get_const_two_irs, stencil_ir, func_ir, index_var) if var_const is not None: return var_const # get index definition index_def = ir_utils.get_definition(stencil_ir, index_var) # match inner_var = unary(index_var) var_const = guard(_get_const_unary_expr, stencil_ir, func_ir, index_def) if var_const is not None: return var_const # match inner_var = arg1 + arg2 var_const = guard(_get_const_binary_expr, stencil_ir, func_ir, index_def) if var_const is not None: return var_const raise GuardException
def dead_branch_prune(func_ir, called_args): """ Removes dead branches based on constant inference from function args. This directly mutates the IR. func_ir is the IR called_args are the actual arguments with which the function is called """ from numba.core.ir_utils import (get_definition, guard, find_const, GuardException) DEBUG = 0 def find_branches(func_ir): # find *all* branches branches = [] for blk in func_ir.blocks.values(): branch_or_jump = blk.body[-1] if isinstance(branch_or_jump, ir.Branch): branch = branch_or_jump pred = guard(get_definition, func_ir, branch.cond.name) if pred is not None and pred.op == "call": function = guard(get_definition, func_ir, pred.func) if (function is not None and isinstance(function, ir.Global) and function.value is bool): condition = guard(get_definition, func_ir, pred.args[0]) if condition is not None: branches.append((branch, condition, blk)) return branches def do_prune(take_truebr, blk): keep = branch.truebr if take_truebr else branch.falsebr # replace the branch with a direct jump jmp = ir.Jump(keep, loc=branch.loc) blk.body[-1] = jmp return 1 if keep == branch.truebr else 0 def prune_by_type(branch, condition, blk, *conds): # this prunes a given branch and fixes up the IR # at least one needs to be a NoneType lhs_cond, rhs_cond = conds lhs_none = isinstance(lhs_cond, types.NoneType) rhs_none = isinstance(rhs_cond, types.NoneType) if lhs_none or rhs_none: try: take_truebr = condition.fn(lhs_cond, rhs_cond) except Exception: return False, None if DEBUG > 0: kill = branch.falsebr if take_truebr else branch.truebr print("Pruning %s" % kill, branch, lhs_cond, rhs_cond, condition.fn) taken = do_prune(take_truebr, blk) return True, taken return False, None def prune_by_value(branch, condition, blk, *conds): lhs_cond, rhs_cond = conds try: take_truebr = condition.fn(lhs_cond, rhs_cond) except Exception: return False, None if DEBUG > 0: kill = branch.falsebr if take_truebr else branch.truebr print("Pruning %s" % kill, branch, lhs_cond, rhs_cond, condition.fn) taken = do_prune(take_truebr, blk) return True, taken def prune_by_predicate(branch, pred, blk): try: # Just to prevent accidents, whilst already guarded, ensure this # is an ir.Const if not isinstance(pred, (ir.Const, ir.FreeVar, ir.Global)): raise TypeError('Expected constant Numba IR node') take_truebr = bool(pred.value) except TypeError: return False, None if DEBUG > 0: kill = branch.falsebr if take_truebr else branch.truebr print("Pruning %s" % kill, branch, pred) taken = do_prune(take_truebr, blk) return True, taken class Unknown(object): pass def resolve_input_arg_const(input_arg_idx): """ Resolves an input arg to a constant (if possible) """ input_arg_ty = called_args[input_arg_idx] # comparing to None? if isinstance(input_arg_ty, types.NoneType): return input_arg_ty # is it a kwarg default if isinstance(input_arg_ty, types.Omitted): val = input_arg_ty.value if isinstance(val, types.NoneType): return val elif val is None: return types.NoneType('none') # literal type, return the type itself so comparisons like `x == None` # still work as e.g. x = types.int64 will never be None/NoneType so # the branch can still be pruned return getattr(input_arg_ty, 'literal_type', Unknown()) if DEBUG > 1: print("before".center(80, '-')) print(func_ir.dump()) phi2lbl = dict() phi2asgn = dict() for lbl, blk in func_ir.blocks.items(): for stmt in blk.body: if isinstance(stmt, ir.Assign): if isinstance(stmt.value, ir.Expr) and stmt.value.op == 'phi': phi2lbl[stmt.value] = lbl phi2asgn[stmt.value] = stmt # This looks for branches where: # at least one arg of the condition is in input args and const # at least one an arg of the condition is a const # if the condition is met it will replace the branch with a jump branch_info = find_branches(func_ir) # stores conditions that have no impact post prune nullified_conditions = [] for branch, condition, blk in branch_info: const_conds = [] if isinstance(condition, ir.Expr) and condition.op == 'binop': prune = prune_by_value for arg in [condition.lhs, condition.rhs]: resolved_const = Unknown() arg_def = guard(get_definition, func_ir, arg) if isinstance(arg_def, ir.Arg): # it's an e.g. literal argument to the function resolved_const = resolve_input_arg_const(arg_def.index) prune = prune_by_type else: # it's some const argument to the function, cannot use guard # here as the const itself may be None try: resolved_const = find_const(func_ir, arg) if resolved_const is None: resolved_const = types.NoneType('none') except GuardException: pass if not isinstance(resolved_const, Unknown): const_conds.append(resolved_const) # lhs/rhs are consts if len(const_conds) == 2: # prune the branch, switch the branch for an unconditional jump prune_stat, taken = prune(branch, condition, blk, *const_conds) if (prune_stat): # add the condition to the list of nullified conditions nullified_conditions.append( nullified(condition, taken, True)) else: # see if this is a branch on a constant value predicate resolved_const = Unknown() try: pred_call = get_definition(func_ir, branch.cond) resolved_const = find_const(func_ir, pred_call.args[0]) if resolved_const is None: resolved_const = types.NoneType('none') except GuardException: pass if not isinstance(resolved_const, Unknown): prune_stat, taken = prune_by_predicate(branch, condition, blk) if (prune_stat): # add the condition to the list of nullified conditions nullified_conditions.append( nullified(condition, taken, False)) # 'ERE BE DRAGONS... # It is the evaluation of the condition expression that often trips up type # inference, so ideally it would be removed as it is effectively rendered # dead by the unconditional jump if a branch was pruned. However, there may # be references to the condition that exist in multiple places (e.g. dels) # and we cannot run DCE here as typing has not taken place to give enough # information to run DCE safely. Upshot of all this is the condition gets # rewritten below into a benign const that typing will be happy with and DCE # can remove it and its reference post typing when it is safe to do so # (if desired). It is required that the const is assigned a value that # indicates the branch taken as its mutated value would be read in the case # of object mode fall back in place of the condition itself. For # completeness the func_ir._definitions and ._consts are also updated to # make the IR state self consistent. deadcond = [x.condition for x in nullified_conditions] for _, cond, blk in branch_info: if cond in deadcond: for x in blk.body: if isinstance(x, ir.Assign) and x.value is cond: # rewrite the condition as a true/false bit nullified_info = nullified_conditions[deadcond.index(cond)] # only do a rewrite of conditions, predicates need to retain # their value as they may be used later. if nullified_info.rewrite_stmt: branch_bit = nullified_info.taken_br x.value = ir.Const(branch_bit, loc=x.loc) # update the specific definition to the new const defns = func_ir._definitions[x.target.name] repl_idx = defns.index(cond) defns[repl_idx] = x.value # Check post dominators of dead nodes from in the original CFG for use of # vars that are being removed in the dead blocks which might be referred to # by phi nodes. # # Multiple things to fix up: # # 1. Cases like: # # A A # |\ | # | B --> B # |/ | # C C # # i.e. the branch is dead but the block is still alive. In this case CFG # simplification will fuse A-B-C and any phi in C can be updated as an # direct assignment from the last assigned version in the dominators of the # fused block. # # 2. Cases like: # # A A # / \ | # B C --> B # \ / | # D D # # i.e. the block C is dead. In this case the phis in D need updating to # reflect the collapse of the phi condition. This should result in a direct # assignment of the surviving version in B to the LHS of the phi in D. new_cfg = compute_cfg_from_blocks(func_ir.blocks) dead_blocks = new_cfg.dead_nodes() # for all phis that are still in live blocks. for phi, lbl in phi2lbl.items(): if lbl in dead_blocks: continue new_incoming = [x[0] for x in new_cfg.predecessors(lbl)] if set(new_incoming) != set(phi.incoming_blocks): # Something has changed in the CFG... if len(new_incoming) == 1: # There's now just one incoming. Replace the PHI node by a # direct assignment idx = phi.incoming_blocks.index(new_incoming[0]) phi2asgn[phi].value = phi.incoming_values[idx] else: # There's more than one incoming still, then look through the # incoming and remove dead ic_val_tmp = [] ic_blk_tmp = [] for ic_val, ic_blk in zip(phi.incoming_values, phi.incoming_blocks): if ic_blk in dead_blocks: continue else: ic_val_tmp.append(ic_val) ic_blk_tmp.append(ic_blk) phi.incoming_values.clear() phi.incoming_values.extend(ic_val_tmp) phi.incoming_blocks.clear() phi.incoming_blocks.extend(ic_blk_tmp) # Remove dead blocks, this is safe as it relies on the CFG only. for dead in dead_blocks: del func_ir.blocks[dead] # if conditions were nullified then consts were rewritten, update if nullified_conditions: func_ir._consts = consts.ConstantInference(func_ir) if DEBUG > 1: print("after".center(80, '-')) print(func_ir.dump())
def get_slice_step(typemap, func_ir, var): require(typemap[var.name] == types.slice3_type) call_expr = get_definition(func_ir, var) require(isinstance(call_expr, ir.Expr) and call_expr.op == 'call') assert len(call_expr.args) == 3 return call_expr.args[2]