bpo-37269: Correctly optimise conditionals with constant booleans (GH-14071)

pablogsal · web-flow · commit 05f831865545 · 2019-06-14T06:54:53.000+01:00
Fix a regression introduced by af8646c that was causing code of the form: if True and False: do_something() to be optimized incorrectly, eliminating the block.
diff --git a/Lib/test/test_peepholer.py b/Lib/test/test_peepholer.py
@@ -414,6 +414,13 @@ def forloop():
                 pass
         self.assertEqual(count_instr_recursively(forloop, 'BUILD_LIST'), 0)
 
+    def test_condition_with_binop_with_bools(self):
+        def f():
+            if True or False:
+                return 1
+            return 0
+        self.assertEqual(f(), 1)
+
 
 class TestBuglets(unittest.TestCase):
 
diff --git a/Misc/NEWS.d/next/Core and Builtins/2019-06-14-06-32-33.bpo-37269.SjVVAe.rst b/Misc/NEWS.d/next/Core and Builtins/2019-06-14-06-32-33.bpo-37269.SjVVAe.rst
@@ -0,0 +1,2 @@
+Fix a bug in the peephole optimizer that was not treating correctly constant
+conditions with binary operators. Patch by Pablo Galindo.
diff --git a/Python/peephole.c b/Python/peephole.c
@@ -315,6 +315,11 @@ PyCode_Optimize(PyObject *code, PyObject* consts, PyObject *names,
                     fill_nops(codestr, op_start, nexti + 1);
                     cumlc = 0;
                 } else if (is_true == 0) {
+                    if (i > 1 &&
+                        (_Py_OPCODE(codestr[i - 1]) == POP_JUMP_IF_TRUE ||
+                         _Py_OPCODE(codestr[i - 1]) == POP_JUMP_IF_FALSE)) {
+                        break;
+                    }
                     h = get_arg(codestr, nexti) / sizeof(_Py_CODEUNIT);
                     tgt = find_op(codestr, codelen, h);
                     fill_nops(codestr, op_start, tgt);

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	`+Fix a bug in the peephole optimizer that was not treating correctly constant`
	`2`	`+conditions with binary operators. Patch by Pablo Galindo.`