bpo-44840: Compiler: Move duplication of exit blocks with no line numbers to after CFG optimization. (GH-27656) (#27673)
(cherry picked from commit b854557b49083d8625a433eb36aacb0c87d67c52)
diff --git a/Python/compile.c b/Python/compile.c
index de2a6bf..edc77e5 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -862,7 +862,7 @@ compiler_copy_block(struct compiler *c, basicblock *block)
* a block can only have one fallthrough predecessor.
*/
assert(block->b_nofallthrough);
- basicblock *result = compiler_next_block(c);
+ basicblock *result = compiler_new_block(c);
if (result == NULL) {
return NULL;
}
@@ -6980,8 +6980,9 @@ normalize_basic_block(basicblock *bb);
static int
optimize_cfg(struct compiler *c, struct assembler *a, PyObject *consts);
+/* Duplicates exit BBs, so that line numbers can be propagated to them */
static int
-ensure_exits_have_lineno(struct compiler *c);
+duplicate_exits_without_lineno(struct compiler *c);
static int
extend_block(basicblock *bb);
@@ -7035,10 +7036,10 @@ guarantee_lineno_for_exits(struct assembler *a, int firstlineno) {
}
struct instr *last = &b->b_instr[b->b_iused-1];
if (last->i_lineno < 0) {
- if (last->i_opcode == RETURN_VALUE)
- {
+ if (last->i_opcode == RETURN_VALUE) {
for (int i = 0; i < b->b_iused; i++) {
assert(b->b_instr[i].i_lineno < 0);
+
b->b_instr[i].i_lineno = lineno;
}
}
@@ -7049,6 +7050,9 @@ guarantee_lineno_for_exits(struct assembler *a, int firstlineno) {
}
}
+static void
+propagate_line_numbers(struct assembler *a);
+
static PyCodeObject *
assemble(struct compiler *c, int addNone)
{
@@ -7081,10 +7085,6 @@ assemble(struct compiler *c, int addNone)
}
}
- if (ensure_exits_have_lineno(c)) {
- return NULL;
- }
-
nblocks = 0;
entryblock = NULL;
for (b = c->u->u_blocks; b != NULL; b = b->b_list) {
@@ -7118,8 +7118,11 @@ assemble(struct compiler *c, int addNone)
if (optimize_cfg(c, &a, consts)) {
goto error;
}
+ if (duplicate_exits_without_lineno(c)) {
+ return NULL;
+ }
+ propagate_line_numbers(&a);
guarantee_lineno_for_exits(&a, c->u->u_firstlineno);
-
/* Can't modify the bytecode after computing jump offsets. */
assemble_jump_offsets(&a, c);
@@ -7691,7 +7694,7 @@ eliminate_empty_basic_blocks(basicblock *entry) {
* but has no impact on the generated line number events.
*/
static void
-propogate_line_numbers(struct assembler *a) {
+propagate_line_numbers(struct assembler *a) {
for (basicblock *b = a->a_entry; b != NULL; b = b->b_next) {
if (b->b_iused == 0) {
continue;
@@ -7748,6 +7751,11 @@ optimize_cfg(struct compiler *c, struct assembler *a, PyObject *consts)
clean_basic_block(b, -1);
assert(b->b_predecessors == 0);
}
+ for (basicblock *b = c->u->u_blocks; b != NULL; b = b->b_list) {
+ if (extend_block(b)) {
+ return -1;
+ }
+ }
if (mark_reachable(a)) {
return -1;
}
@@ -7792,7 +7800,6 @@ optimize_cfg(struct compiler *c, struct assembler *a, PyObject *consts)
if (maybe_empty_blocks) {
eliminate_empty_basic_blocks(a->a_entry);
}
- propogate_line_numbers(a);
return 0;
}
@@ -7811,7 +7818,7 @@ is_exit_without_lineno(basicblock *b) {
* copy the line number from the sole predecessor block.
*/
static int
-ensure_exits_have_lineno(struct compiler *c)
+duplicate_exits_without_lineno(struct compiler *c)
{
basicblock *entry = NULL;
/* Copy all exit blocks without line number that are targets of a jump.
@@ -7826,21 +7833,22 @@ ensure_exits_have_lineno(struct compiler *c)
continue;
}
basicblock *target = b->b_instr[b->b_iused-1].i_target;
- if (is_exit_without_lineno(target)) {
+ if (is_exit_without_lineno(target) && target->b_predecessors > 1) {
basicblock *new_target = compiler_copy_block(c, target);
if (new_target == NULL) {
return -1;
}
new_target->b_instr[0].i_lineno = b->b_instr[b->b_iused-1].i_lineno;
b->b_instr[b->b_iused-1].i_target = new_target;
+ target->b_predecessors--;
+ new_target->b_predecessors = 1;
+ new_target->b_next = target->b_next;
+ target->b_next = new_target;
}
}
entry = b;
}
assert(entry != NULL);
- if (is_exit_without_lineno(entry)) {
- entry->b_instr[0].i_lineno = c->u->u_firstlineno;
- }
/* Eliminate empty blocks */
for (basicblock *b = c->u->u_blocks; b != NULL; b = b->b_list) {
while (b->b_next && b->b_next->b_iused == 0) {