bpo-44626: Merge basic blocks earlier to enable better handling of exit blocks without line numbers (GH-27138) (GH-27182)
(cherry picked from commit a86f7dae0acf918d54086cb85e5a0b0bedeedce7)
diff --git a/Python/compile.c b/Python/compile.c
index 9b7ce19..46660f2 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -6934,10 +6934,11 @@ makecode(struct compiler *c, struct assembler *a, PyObject *consts)
/* For debugging purposes only */
#if 0
static void
-dump_instr(const struct instr *i)
+dump_instr(struct instr *i)
{
- const char *jrel = (is_relative_jump(instr)) ? "jrel " : "";
- const char *jabs = (is_jump(instr) && !is_relative_jump(instr))? "jabs " : "";
+ const char *jrel = (is_relative_jump(i)) ? "jrel " : "";
+ const char *jabs = (is_jump(i) && !is_relative_jump(i))? "jabs " : "";
+
char arg[128];
*arg = '\0';
@@ -6975,6 +6976,9 @@ static int
ensure_exits_have_lineno(struct compiler *c);
static int
+extend_block(basicblock *bb);
+
+static int
insert_generator_prefix(struct compiler *c, basicblock *entryblock) {
int flags = compute_code_flags(c);
@@ -7063,6 +7067,12 @@ assemble(struct compiler *c, int addNone)
}
}
+ for (basicblock *b = c->u->u_blocks; b != NULL; b = b->b_list) {
+ if (extend_block(b)) {
+ return NULL;
+ }
+ }
+
if (ensure_exits_have_lineno(c)) {
return NULL;
}
@@ -7096,6 +7106,7 @@ assemble(struct compiler *c, int addNone)
if (consts == NULL) {
goto error;
}
+
if (optimize_cfg(c, &a, consts)) {
goto error;
}
@@ -7459,19 +7470,14 @@ optimize_basic_block(struct compiler *c, basicblock *bb, PyObject *consts)
goto error;
}
break;
- default:
- if (inst->i_target->b_exit && inst->i_target->b_iused <= MAX_COPY_SIZE) {
- basicblock *to_copy = inst->i_target;
- inst->i_opcode = NOP;
- for (i = 0; i < to_copy->b_iused; i++) {
- int index = compiler_next_instr(bb);
- if (index < 0) {
- return -1;
- }
- bb->b_instr[index] = to_copy->b_instr[i];
- }
- bb->b_exit = 1;
- }
+ }
+ break;
+ case FOR_ITER:
+ assert (i == bb->b_iused-1);
+ if (target->i_opcode == JUMP_FORWARD) {
+ if (eliminate_jump_to_jump(bb, inst->i_opcode)) {
+ goto error;
+ }
}
break;
case ROT_N:
@@ -7501,6 +7507,32 @@ optimize_basic_block(struct compiler *c, basicblock *bb, PyObject *consts)
return -1;
}
+/* If this block ends with an unconditional jump to an exit block,
+ * then remove the jump and extend this block with the target.
+ */
+static int
+extend_block(basicblock *bb) {
+ if (bb->b_iused == 0) {
+ return 0;
+ }
+ struct instr *last = &bb->b_instr[bb->b_iused-1];
+ if (last->i_opcode != JUMP_ABSOLUTE && last->i_opcode != JUMP_FORWARD) {
+ return 0;
+ }
+ if (last->i_target->b_exit && last->i_target->b_iused <= MAX_COPY_SIZE) {
+ basicblock *to_copy = last->i_target;
+ last->i_opcode = NOP;
+ for (int i = 0; i < to_copy->b_iused; i++) {
+ int index = compiler_next_instr(bb);
+ if (index < 0) {
+ return -1;
+ }
+ bb->b_instr[index] = to_copy->b_instr[i];
+ }
+ bb->b_exit = 1;
+ }
+ return 0;
+}
static void
clean_basic_block(basicblock *bb, int prev_lineno) {