fix: bb_test_pop_if_false not setting flag (python#24)

Python/bytecodes.c

@@ -1977,6 +1977,7 @@ dummy_func(
                 }
                 else {
                     ERROR_IF(err < 0, error);
+                    bb_test = BB_TEST(1, 0);
                 }
             }
         }
@@ -2018,6 +2019,7 @@ dummy_func(
                 }
                 else {
                     ERROR_IF(err < 0, error);
+                    bb_test = BB_TEST(1, 0);
                 }
             }
         }

Python/tier2.c

@@ -1131,6 +1131,7 @@ emit_type_guard(_Py_CODEUNIT *write_curr, int guard_opcode, int guard_oparg, int
     fprintf(stderr, "emitted type guard %p %s\n", write_curr,
         _PyOpcode_OpName[guard_opcode]);
 #endif
+    assert(guard_oparg <= 0xFF);
     write_curr->op.code = guard_opcode;
     write_curr->op.arg = guard_oparg & 0xFF;
     write_curr++;
@@ -3009,6 +3010,7 @@ _PyTier2_RewriteForwardJump(_Py_CODEUNIT *bb_branch, _Py_CODEUNIT *target)
     }
     else {
         _py_set_opcode(write_curr, NOP);
+        write_curr->op.arg = 0;
         write_curr++;
     }
     _py_set_opcode(write_curr,
@@ -3064,6 +3066,7 @@ _PyTier2_RewriteBackwardJump(_Py_CODEUNIT *jump_backward_lazy, _Py_CODEUNIT *tar
     }
     else {
         _py_set_opcode(write_curr, NOP);
+        write_curr->op.arg = 0;
         write_curr++;
     }
     _py_set_opcode(write_curr, is_backwards_jump

tier2_test.py

@@ -493,4 +493,30 @@ def f(x,l):
 
     # As long as it doesn't crash, everything's good.
 
+######################################################################
+# Tests for: Tier 2 BB_TEST_POP_IF_FALSE flag setting                #
+######################################################################
+with TestInfo("tier 2 BB_TEST_POP_IF_FALSE flag setting"):
+    # See https://github.com/pylbbv/pylbbv/issues/23 for more information.
+    import sys
+
+    class A:
+        def __init__(self): ...
+        def __add__(self, _): return "Hewwo!"
+
+    def f(a):
+        b = 1
+        if a: b = A()
+        print(b)
+        return b+b
+
+
+    for _ in range(63): f(0)
+
+    assert f(1) == "Hewwo!"
+
+    assert f(0) == 2
+
+    # As long as it doesn't crash, everything's good.
+
 print("Tests completed ^-^")