[mypyc] Ignore super calls to object.__init__() (#11938)

This speeds up the deltablue benchmark by 15%.

Author: JukkaL

mypyc/irbuild/expression.py

@@ -326,11 +326,20 @@ def translate_super_method_call(builder: IRBuilder, expr: CallExpr, callee: Supe
             return translate_call(builder, expr, callee)
 
     ir = builder.mapper.type_to_ir[callee.info]
-    # Search for the method in the mro, skipping ourselves.
+    # Search for the method in the mro, skipping ourselves. We
+    # determine targets of super calls to native methods statically.
     for base in ir.mro[1:]:
         if callee.name in base.method_decls:
             break
     else:
+        if (ir.is_ext_class
+                and ir.builtin_base is None
+                and not ir.inherits_python
+                and callee.name == '__init__'
+                and len(expr.args) == 0):
+            # Call translates to object.__init__(self), which is a
+            # no-op, so omit the call.
+            return builder.none()
         return translate_call(builder, expr, callee)
 
     decl = base.method_decl(callee.name)

mypyc/test-data/irbuild-classes.test

@@ -795,6 +795,53 @@ L0:
     r0 = T.foo(self)
     return 1
 
+[case testSuperCallToObjectInitIsOmitted]
+class C:
+    def __init__(self) -> None:
+        super().__init__()
+class D: pass
+class E(D):
+    def __init__(self) -> None:
+        super().__init__()
+class F(C):
+    def __init__(self) -> None:
+        super().__init__()
+class DictSubclass(dict):
+    def __init__(self) -> None:
+        super().__init__()
+[out]
+def C.__init__(self):
+    self :: __main__.C
+L0:
+    return 1
+def E.__init__(self):
+    self :: __main__.E
+L0:
+    return 1
+def F.__init__(self):
+    self :: __main__.F
+    r0 :: None
+L0:
+    r0 = C.__init__(self)
+    return 1
+def DictSubclass.__init__(self):
+    self :: dict
+    r0 :: object
+    r1 :: str
+    r2, r3, r4 :: object
+    r5 :: str
+    r6, r7 :: object
+L0:
+    r0 = builtins :: module
+    r1 = 'super'
+    r2 = CPyObject_GetAttr(r0, r1)
+    r3 = __main__.DictSubclass :: type
+    r4 = PyObject_CallFunctionObjArgs(r2, r3, self, 0)
+    r5 = '__init__'
+    r6 = CPyObject_GetAttr(r4, r5)
+    r7 = PyObject_CallFunctionObjArgs(r6, 0)
+    return 1
+
 [case testClassVariable]
 from typing import ClassVar
 class A: