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python-uncompyle6/uncompyle6/parsers/reducecheck/ifstmts_jump.py
2024-03-14 05:39:30 -04:00

46 lines
1.7 KiB
Python

# Copyright (c) 2020 Rocky Bernstein
from uncompyle6.scanners.tok import Token
def ifstmts_jump(self, lhs, n, rule, ast, tokens, first, last):
if len(rule[1]) <= 1 or not ast:
return False
come_froms = ast[-1]
# This is complicated, but note that the JUMP_IF instruction comes immediately
# *before* _ifstmts_jump so that's what we have to test
# the COME_FROM against. This can be complicated by intervening
# POP_TOP, and pseudo COME_FROM, ELSE instructions
#
pop_jump_index = first - 1
while pop_jump_index > 0 and tokens[pop_jump_index] in (
"ELSE",
"POP_TOP",
"JUMP_FORWARD",
"COME_FROM",
):
pop_jump_index -= 1
# FIXME: something is fishy when and EXTENDED ARG is needed before the
# pop_jump_index instruction to get the argument. In this case, the
# _ifsmtst_jump can jump to a spot beyond the come_froms.
# That is going on in the non-EXTENDED_ARG case is that the POP_JUMP_IF
# jumps to a JUMP_(FORWARD) which is changed into an EXTENDED_ARG POP_JUMP_IF
# to the jumped forwarded address
if tokens[pop_jump_index].attr > 256:
return False
pop_jump_offset = tokens[pop_jump_index].off2int(prefer_last=False)
if isinstance(come_froms, Token):
if tokens[pop_jump_index].attr < pop_jump_offset and ast[0] != "pass":
# This is a jump backwards to a loop. All bets are off here when there the
# unless statement is "pass" which has no instructions associated with it.
return False
return come_froms.attr is not None and pop_jump_offset > come_froms.attr
elif len(come_froms) == 0:
return False
else:
return pop_jump_offset > come_froms[-1].attr