1 files changed, 9 insertions, 5 deletions
diff --git a/Python/peephole.c b/Python/peephole.c
index 1ce3535626..6f3e2ed88b 100644
--- a/Python/peephole.c
+++ b/Python/peephole.c
@@ -250,12 +250,16 @@ PyCode_Optimize(PyObject *code, PyObject* consts, PyObject *names,
     lnotab = (unsigned char*)PyBytes_AS_STRING(lnotab_obj);
     tabsiz = PyBytes_GET_SIZE(lnotab_obj);
     assert(tabsiz == 0 || Py_REFCNT(lnotab_obj) == 1);
-    if (memchr(lnotab, 255, tabsiz) != NULL) {
-        /* 255 value are used for multibyte bytecode instructions */
-        goto exitUnchanged;
+
+    /* Don't optimize if lnotab contains instruction pointer delta larger
+       than +255 (encoded as multiple bytes), just to keep the peephole optimizer
+       simple. The optimizer leaves line number deltas unchanged. */
+
+    for (j = 0; j < tabsiz; j += 2) {
+        if (lnotab[j] == 255) {
+            goto exitUnchanged;
+        }
     }
-    /* Note: -128 and 127 special values for line number delta are ok,
-       the peephole optimizer doesn't modify line numbers. */
 
     assert(PyBytes_Check(code));
     Py_ssize_t codesize = PyBytes_GET_SIZE(code);