Avoid slow Pythran dtype checking code in fused function dispatch if pythran is not used.

Cython/Compiler/FusedNode.py

@@ -424,7 +424,7 @@ class FusedCFuncDefNode(StatListNode):
                 if ndarray is not None:
                     if isinstance(arg, ndarray):
                         dtype = arg.dtype
-                        arg_is_pythran_compatible = True
+                        """ + ("arg_is_pythran_compatible = True" if pythran_types else "") + """
                     elif __pyx_memoryview_check(arg):
                         arg_base = arg.base
                         if isinstance(arg_base, ndarray):
@@ -438,24 +438,30 @@ class FusedCFuncDefNode(StatListNode):
                     if dtype is not None:
                         itemsize = dtype.itemsize
                         kind = ord(dtype.kind)
+                        dtype_signed = kind == 'i'
+            """)
+        pyx_code.indent(2)
+        if pythran_types:
+            pyx_code.put_chunk(
+                u"""
                         # We only support the endianness of the current compiler
                         byteorder = dtype.byteorder
                         if byteorder == "<" and not __Pyx_Is_Little_Endian():
                             arg_is_pythran_compatible = False
-                        if byteorder == ">" and __Pyx_Is_Little_Endian():
+                        elif byteorder == ">" and __Pyx_Is_Little_Endian():
                             arg_is_pythran_compatible = False
-                        dtype_signed = kind == 'i'
                         if arg_is_pythran_compatible:
                             cur_stride = itemsize
-                            for dim,stride in zip(reversed(arg.shape),reversed(arg.strides)):
-                                if stride != cur_stride:
+                            shape = arg.shape
+                            strides = arg.strides
+                            for i in range(arg.ndim):
+                                if strides[i] != cur_stride:
                                     arg_is_pythran_compatible = False
                                     break
-                                cur_stride *= dim
+                                cur_stride *= shape[i]
                             else:
                                 arg_is_pythran_compatible = not (arg.flags.f_contiguous and arg.ndim > 1)
                 """)
-        pyx_code.indent(2)
         pyx_code.named_insertion_point("numpy_dtype_checks")
         self._buffer_check_numpy_dtype(pyx_code, buffer_types, pythran_types)
         pyx_code.dedent(2)
@@ -464,7 +470,7 @@ class FusedCFuncDefNode(StatListNode):
             self._buffer_parse_format_string_check(
                     pyx_code, decl_code, specialized_type, env)
 
-    def _buffer_declarations(self, pyx_code, decl_code, all_buffer_types):
+    def _buffer_declarations(self, pyx_code, decl_code, all_buffer_types, pythran_types):
         """
         If we have any buffer specializations, write out some variable
         declarations and imports.
@@ -484,9 +490,13 @@ class FusedCFuncDefNode(StatListNode):
                 cdef Py_ssize_t itemsize
                 cdef bint dtype_signed
                 cdef char kind
-                cdef bint arg_is_pythran_compatible
 
                 itemsize = -1
+            """)
+
+        if pythran_types:
+            pyx_code.local_variable_declarations.put_chunk(u"""
+                cdef bint arg_is_pythran_compatible
                 arg_is_pythran_compatible = False
             """)
 
@@ -670,7 +680,7 @@ class FusedCFuncDefNode(StatListNode):
                 default_idx += 1
 
         if all_buffer_types:
-            self._buffer_declarations(pyx_code, decl_code, all_buffer_types)
+            self._buffer_declarations(pyx_code, decl_code, all_buffer_types, pythran_types)
             env.use_utility_code(Code.UtilityCode.load_cached("Import", "ImportExport.c"))
             env.use_utility_code(Code.UtilityCode.load_cached("ImportNumPyArray", "ImportExport.c"))