diff options
Diffstat (limited to 'Python/compile.c')
| -rw-r--r-- | Python/compile.c | 42 |
1 files changed, 42 insertions, 0 deletions
diff --git a/Python/compile.c b/Python/compile.c index ae92869fc9..4792733fd5 100644 --- a/Python/compile.c +++ b/Python/compile.c @@ -6437,8 +6437,50 @@ optimize_cfg(struct assembler *a, PyObject *consts) for (basicblock *b = a->a_entry; b != NULL; b = b->b_next) { if (b->b_reachable == 0) { b->b_iused = 0; + b->b_nofallthrough = 0; } } + /* Delete jump instructions made redundant by previous step. If a non-empty + block ends with a jump instruction, check if the next non-empty block + reached through normal flow control is the target of that jump. If it + is, then the jump instruction is redundant and can be deleted. + */ + for (basicblock *b = a->a_entry; b != NULL; b = b->b_next) { + if (b->b_iused > 0) { + struct instr *b_last_instr = &b->b_instr[b->b_iused - 1]; + if (b_last_instr->i_opcode == POP_JUMP_IF_FALSE || + b_last_instr->i_opcode == POP_JUMP_IF_TRUE || + b_last_instr->i_opcode == JUMP_ABSOLUTE || + b_last_instr->i_opcode == JUMP_FORWARD) { + basicblock *b_next_act = b->b_next; + while (b_next_act != NULL && b_next_act->b_iused == 0) { + b_next_act = b_next_act->b_next; + } + if (b_last_instr->i_target == b_next_act) { + b->b_nofallthrough = 0; + switch(b_last_instr->i_opcode) { + case POP_JUMP_IF_FALSE: + case POP_JUMP_IF_TRUE: + b_last_instr->i_opcode = POP_TOP; + b_last_instr->i_target = NULL; + b_last_instr->i_oparg = 0; + break; + case JUMP_ABSOLUTE: + case JUMP_FORWARD: + b_last_instr->i_opcode = NOP; + clean_basic_block(b); + break; + } + /* The blocks after this one are now reachable through it */ + b_next_act = b->b_next; + while (b_next_act != NULL && b_next_act->b_iused == 0) { + b_next_act->b_reachable = 1; + b_next_act = b_next_act->b_next; + } + } + } + } + } minimize_lineno_table(a); return 0; } |