Jump-To-Jump elimination could be more aggressive. #93223
Description
Example:
def f(): for i in range(5): if i > 3: print(i) 1 0 RESUME 0 2 2 LOAD_GLOBAL 1 (NULL + range) 14 LOAD_CONST 1 (5) 16 CALL 1 26 GET_ITER >> 28 FOR_ITER 21 (to 72) 30 STORE_FAST 0 (i) 3 32 LOAD_FAST 0 (i) 34 LOAD_CONST 2 (3) 36 COMPARE_OP 4 (>) 42 POP_JUMP_FORWARD_IF_FALSE 13 (to 70) <--------- could be BACKWARD to 28 4 44 LOAD_GLOBAL 3 (NULL + print) 56 LOAD_FAST 0 (i) 58 CALL 1 68 POP_TOP >> 70 JUMP_BACKWARD 22 (to 28) 2 >> 72 LOAD_CONST 0 (None) 74 RETURN_VALUE Something like this should suffice:
static bool jump_thread(struct instr *inst, struct instr *target, int opcode) { assert(!IS_VIRTUAL_OPCODE(opcode) || IS_VIRTUAL_JUMP_OPCODE(opcode)); assert(is_jump(inst)); assert(is_jump(target)); // bpo-45773: If inst->i_target == target->i_target, then nothing actually // changes (and we fall into an infinite loop): - if (inst->i_lineno == target->i_lineno && + if ((inst->i_lineno == target->i_lineno || target->i_lineno == -1) && inst->i_target != target->i_target) { inst->i_target = target->i_target; inst->i_opcode = opcode; return true; } return false; }