Move apply_static_swap to the last phase of bb optimization

Author: corona10

Lib/test/test_peepholer.py

@@ -1074,9 +1074,7 @@ def test_no_unsafe_static_swap(self):
         expected_insts = [
             ('LOAD_CONST', 0, 1),
             ('LOAD_CONST', 1, 2),
-            ('LOAD_CONST', 2, 3),
-            ('SWAP', 3, 4),
-            ('POP_TOP', 0, 4),
+            ('NOP', 0, 3),
             ('STORE_FAST', 1, 4),
             ('POP_TOP', 0, 4),
             ('RETURN_VALUE', 5)
@@ -1096,7 +1094,7 @@ def test_dead_store_elimination_in_same_lineno(self):
         expected_insts = [
             ('LOAD_CONST', 0, 1),
             ('LOAD_CONST', 1, 2),
-            ('NOP', None, 3),
+            ('NOP', 0, 3),
             ('POP_TOP', 0, 4),
             ('STORE_FAST', 1, 4),
             ('RETURN_VALUE', 5)

Python/flowgraph.c

@@ -1526,12 +1526,7 @@ optimize_basic_block(PyObject *const_cache, basicblock *bb, PyObject *consts)
             case SWAP:
                 if (oparg == 1) {
                     INSTR_SET_OP0(inst, NOP);
-                    break;
-                }
-                if (swaptimize(bb, &i) < 0) {
-                    goto error;
                 }
-                apply_static_swaps(bb, i);
                 break;
             case KW_NAMES:
                 break;
@@ -1546,6 +1541,15 @@ optimize_basic_block(PyObject *const_cache, basicblock *bb, PyObject *consts)
                 assert (!HAS_CONST(inst->i_opcode));
         }
     }
+    for (int i = 0; i < bb->b_iused; i++) {
+        cfg_instr *inst = &bb->b_instr[i];
+        if (inst->i_opcode == SWAP) {
+            if (swaptimize(bb, &i) < 0) {
+                goto error;
+            }
+            apply_static_swaps(bb, i);
+        }
+    }
     return SUCCESS;
 error:
     return ERROR;