pythongh-113054: Compiler no longer replaces a redundant jump with no…

… line number by a NOP (python#113139)

Lib/test/test_compile.py

@@ -444,6 +444,10 @@ def f():
  self.assertIn("_A__mangled_mod", A.f.__code__.co_varnames)
  self.assertIn("__package__", A.f.__code__.co_varnames)
 
+ def test_condition_expression_with_dead_blocks_compiles(self):
+ # See gh-113054
+ compile('if (5 if 5 else T): 0', '<eval>', 'exec')
+
  def test_compile_invalid_namedexpr(self):
  # gh-109351
  m = ast.Module(

Misc/NEWS.d/next/Core and Builtins/2023-12-14-20-08-35.gh-issue-113054.e20CtM.rst

@@ -0,0 +1,2 @@
+Fixed bug where a redundant NOP is not removed, causing an assertion to fail
+in the compiler in debug mode.

Python/flowgraph.c

@@ -1110,7 +1110,10 @@ remove_redundant_jumps(cfg_builder *g) {
  * of that jump. If it is, then the jump instruction is redundant and
  * can be deleted.
  */
+
  assert(no_empty_basic_blocks(g));
+
+ bool remove_empty_blocks = false;
  for (basicblock *b = g->g_entryblock; b != NULL; b = b->b_next) {
  cfg_instr *last = basicblock_last_instr(b);
  assert(last != NULL);
@@ -1122,10 +1125,22 @@ remove_redundant_jumps(cfg_builder *g) {
  }
  if (last->i_target == b->b_next) {
  assert(b->b_next->b_iused);
- INSTR_SET_OP0(last, NOP);
+ if (last->i_loc.lineno == NO_LOCATION.lineno) {
+ b->b_iused--;
+ if (b->b_iused == 0) {
+ remove_empty_blocks = true;
+ }
+ }
+ else {
+ INSTR_SET_OP0(last, NOP);
+ }
  }
  }
  }
+ if (remove_empty_blocks) {
+ eliminate_empty_basic_blocks(g);
+ }
+ assert(no_empty_basic_blocks(g));
  return SUCCESS;
 }