pythongh-109823: Adjust labels in compiler when removing an empty bas…

…ic block which is a jump target
iritkatriel · Sep 25, 2023 · 29070c5 · 29070c5
1 parent f2eaa92
commit 29070c5
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Showing 2 changed files with 13 additions and 1 deletion.
diff --git a/Lib/test/test_compile.py b/Lib/test/test_compile.py
@@ -1272,6 +1272,11 @@ def f():
             else:
                 1 if 1 else 1
 
+    def test_remove_empty_basic_block_with_jump_target_label(self):
+        # See gh-109823
+        def f(x):
+            while x:
+                0 if 1 else 0
 
 @requires_debug_ranges()
 class TestSourcePositions(unittest.TestCase):

diff --git a/Python/flowgraph.c b/Python/flowgraph.c
@@ -960,6 +960,7 @@ eliminate_empty_basic_blocks(cfg_builder *g) {
     while(g->g_entryblock && g->g_entryblock->b_iused == 0) {
         g->g_entryblock = g->g_entryblock->b_next;
     }
+    int next_lbl = get_max_label(g->g_entryblock) + 1;
     for (basicblock *b = g->g_entryblock; b != NULL; b = b->b_next) {
         assert(b->b_iused > 0);
         for (int i = 0; i < b->b_iused; i++) {
@@ -969,7 +970,13 @@ eliminate_empty_basic_blocks(cfg_builder *g) {
                 while (target->b_iused == 0) {
                     target = target->b_next;
                 }
-                instr->i_target = target;
+                if (instr->i_target != target) {
+                    if (!IS_LABEL(target->b_label)) {
+                        target->b_label.id = next_lbl++;
+                    }
+                    instr->i_target = target;
+                    instr->i_oparg = target->b_label.id;
+                }
                 assert(instr->i_target && instr->i_target->b_iused > 0);
             }
         }