optimise left-shift operations with small integers

CHANGES.rst

@@ -34,6 +34,8 @@ Features added
 
 * Speed up cython.inline().
 
+* Binary lshift operations with small constant Python integers are faster.
+
 Bugs fixed
 ----------
 

Cython/Compiler/Optimize.py

@@ -2933,6 +2933,13 @@ class OptimizeBuiltinCalls(Visitor.NodeRefCleanupMixin,
             return node
         return self._optimise_num_binop('Rshift', node, function, args, is_unbound_method)
 
+    def _handle_simple_method_object___lshift__(self, node, function, args, is_unbound_method):
+        if len(args) != 2 or not isinstance(args[1], ExprNodes.IntNode):
+            return node
+        if not args[1].has_constant_result() or not (1 <= args[1].constant_result <= 63):
+            return node
+        return self._optimise_num_binop('Lshift', node, function, args, is_unbound_method)
+
     def _handle_simple_method_object___mod__(self, node, function, args, is_unbound_method):
         return self._optimise_num_div('Remainder', node, function, args, is_unbound_method)
 

Cython/Utility/Optimize.c

@@ -536,7 +536,7 @@ static PyObject* __Pyx_PyInt_{{op}}{{order}}(PyObject *op1, PyObject *op2, long
 {{py:
 c_op = {
     'Add': '+', 'Subtract': '-', 'Remainder': '%', 'TrueDivide': '/', 'FloorDivide': '/',
-    'Or': '|', 'Xor': '^', 'And': '&', 'Rshift': '>>',
+    'Or': '|', 'Xor': '^', 'And': '&', 'Rshift': '>>', 'Lshift': '<<',
     'Eq': '==', 'Ne': '!=',
     }[op]
 }}
@@ -593,6 +593,10 @@ static PyObject* __Pyx_PyInt_{{op}}{{order}}(PyObject *op1, PyObject *op2, CYTHO
                 x = q;
             }
             return PyInt_FromLong(x);
+        {{elif op == 'Lshift'}}
+            if (likely(a == (a << b) >> b)) {
+                return PyInt_FromLong(a {{c_op}} b);
+            }
         {{else}}
             // other operations are safe, no overflow
             return PyInt_FromLong(a {{c_op}} b);
@@ -673,6 +677,12 @@ static PyObject* __Pyx_PyInt_{{op}}{{order}}(PyObject *op1, PyObject *op2, CYTHO
                 }
             {{else}}
                 x = a {{c_op}} b;
+                {{if op == 'Lshift'}}
+                if (unlikely(a != x >> b)) {
+                    ll{{ival}} = {{ival}};
+                    goto long_long;
+                }
+                {{endif}}
             {{endif}}
             return PyLong_FromLong(x);
 
@@ -693,6 +703,9 @@ static PyObject* __Pyx_PyInt_{{op}}{{order}}(PyObject *op1, PyObject *op2, CYTHO
                 }
             {{else}}
                 llx = lla {{c_op}} llb;
+                {{if op == 'Lshift'}}
+                if (likely(lla == llx >> llb)) /* then execute 'return' below */
+                {{endif}}
             {{endif}}
             return PyLong_FromLongLong(llx);
         {{endif}}

tests/run/pyintop.pyx

@@ -5,6 +5,10 @@ def bigint(x):
     # avoid 'L' postfix in Py2.x
     print(str(x).rstrip('L'))
 
+def bigints(x):
+    # avoid 'L' postfix in Py2.x
+    print(str(x).replace('L', ''))
+
 
 def or_obj(obj2, obj3):
     """
@@ -130,6 +134,61 @@ def rshift_int(obj2):
     return obj1
 
 
+def lshift_int(obj):
+    """
+    >>> lshift_int(0)
+    (0, 0, 0, 0)
+    >>> bigints(lshift_int(1))
+    (8, 2147483648, 9223372036854775808, 10633823966279326983230456482242756608)
+    >>> bigints(lshift_int(-1))
+    (-8, -2147483648, -9223372036854775808, -10633823966279326983230456482242756608)
+    >>> bigints(lshift_int(2))
+    (16, 4294967296, 18446744073709551616, 21267647932558653966460912964485513216)
+
+    >>> bigints(lshift_int(27))
+    (216, 57982058496, 249031044995078946816, 287113247089541828547222325020554428416)
+    >>> (-27) << 3
+    -216
+    >>> bigints(lshift_int(-27))
+    (-216, -57982058496, -249031044995078946816, -287113247089541828547222325020554428416)
+
+    >>> bigints(lshift_int(32))
+    (256, 68719476736, 295147905179352825856, 340282366920938463463374607431768211456)
+    >>> (-32) << 3
+    -256
+    >>> bigints(lshift_int(-32))
+    (-256, -68719476736, -295147905179352825856, -340282366920938463463374607431768211456)
+
+    >>> (2**28) << 3
+    2147483648
+    >>> bigints(lshift_int(2**28))
+    (2147483648, 576460752303423488, 2475880078570760549798248448, 2854495385411919762116571938898990272765493248)
+    >>> (-2**28) << 3
+    -2147483648
+    >>> bigints(lshift_int(-2**28))
+    (-2147483648, -576460752303423488, -2475880078570760549798248448, -2854495385411919762116571938898990272765493248)
+
+    >>> (2**30) << 3
+    8589934592
+    >>> bigints(lshift_int(2**30))
+    (8589934592, 2305843009213693952, 9903520314283042199192993792, 11417981541647679048466287755595961091061972992)
+    >>> bigints(lshift_int(-2**30))
+    (-8589934592, -2305843009213693952, -9903520314283042199192993792, -11417981541647679048466287755595961091061972992)
+
+    >>> bigint((2**60) << 3)
+    9223372036854775808
+    >>> bigints(lshift_int(2**60))
+    (9223372036854775808, 2475880078570760549798248448, 10633823966279326983230456482242756608, 12259964326927110866866776217202473468949912977468817408)
+    >>> bigints(lshift_int(-2**60))
+    (-9223372036854775808, -2475880078570760549798248448, -10633823966279326983230456482242756608, -12259964326927110866866776217202473468949912977468817408)
+    """
+    r1 = obj << 3
+    r2 = obj << 31
+    r3 = obj << 63
+    r4 = obj << 123
+    return r1, r2, r3, r4
+
+
 def mixed_obj(obj2, obj3):
     """
     >>> mixed_obj(2, 3)