optimise Python float modulus

Cython/Compiler/Optimize.py

@@ -2852,11 +2852,7 @@ class OptimizeBuiltinCalls(Visitor.NodeRefCleanupMixin,
         return self._optimise_num_binop('Rshift', node, function, args, is_unbound_method)
 
     def _handle_simple_method_object___mod__(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 (2 <= args[1].constant_result <= 2**30):
-            return node
-        return self._optimise_num_binop('Remainder', node, function, args, is_unbound_method)
+        return self._optimise_num_div('Remainder', node, function, args, is_unbound_method)
 
     def _handle_simple_method_object___floordiv__(self, node, function, args, is_unbound_method):
         return self._optimise_num_div('FloorDivide', node, function, args, is_unbound_method)
@@ -2892,6 +2888,9 @@ class OptimizeBuiltinCalls(Visitor.NodeRefCleanupMixin,
     def _handle_simple_method_float___div__(self, node, function, args, is_unbound_method):
         return self._optimise_num_binop('Divide', node, function, args, is_unbound_method)
 
+    def _handle_simple_method_float___mod__(self, node, function, args, is_unbound_method):
+        return self._optimise_num_binop('Remainder', node, function, args, is_unbound_method)
+
     def _handle_simple_method_float___eq__(self, node, function, args, is_unbound_method):
         return self._optimise_num_binop('Eq', node, function, args, is_unbound_method)
 
@@ -2928,7 +2927,7 @@ class OptimizeBuiltinCalls(Visitor.NodeRefCleanupMixin,
 
         is_float = isinstance(numval, ExprNodes.FloatNode)
         if is_float:
-            if operator not in ('Add', 'Subtract', 'TrueDivide', 'Divide', 'Eq', 'Ne'):
+            if operator not in ('Add', 'Subtract', 'Remainder', 'TrueDivide', 'Divide', 'Eq', 'Ne'):
                 return node
         elif operator == 'Divide':
             # mixed old-/new-style division is not currently optimised for integers

Cython/Utility/Optimize.c

@@ -687,7 +687,7 @@ static PyObject* __Pyx_PyFloat_{{op}}{{order}}(PyObject *op1, PyObject *op2, dou
 {{py: pyval, fval = ('op2', 'b') if order == 'CObj' else ('op1', 'a') }}
 {{py:
 c_op = {
-    'Add': '+', 'Subtract': '-', 'TrueDivide': '/', 'Divide': '/',
+    'Add': '+', 'Subtract': '-', 'TrueDivide': '/', 'Divide': '/', 'Remainder': '%',
     'Eq': '==', 'Ne': '!=',
     }[op]
 }}
@@ -768,7 +768,15 @@ static PyObject* __Pyx_PyFloat_{{op}}{{order}}(PyObject *op1, PyObject *op2, dou
     {{else}}
         // copied from floatobject.c in Py3.5:
         PyFPE_START_PROTECT("{{op.lower() if not op.endswith('Divide') else 'divide'}}", return NULL)
+        {{if c_op == '%'}}
+        result = fmod(a, b);
+        if (result)
+            result += ((result < 0) ^ (b < 0)) * b;
+        else
+            result = copysign(0.0, b);
+        {{else}}
         result = a {{c_op}} b;
+        {{endif}}
         PyFPE_END_PROTECT(result)
         return PyFloat_FromDouble(result);
     {{endif}}

tests/run/modop.pyx

@@ -173,6 +173,25 @@ def mod_obj_m2(int2):
     return int1
 
 
+def mod_obj_m2f(obj2):
+    """
+    >>> 0 % -2.0
+    -0.0
+    >>> mod_obj_m2f(0)
+    -0.0
+    >>> 1 % -2.0
+    -1.0
+    >>> mod_obj_m2f(1)
+    -1.0
+    >>> 9 % -2.0
+    -1.0
+    >>> mod_obj_m2f(9)
+    -1.0
+    """
+    result = obj2 % -2.0
+    return result
+
+
 def modint(int int2, int int3):
     """
     >>> modint(9,2)