Add a custom mapper.

For some reason I need that subst variable...

python/dune/perftool/target.py

@@ -7,6 +7,9 @@ from loopy.target.c.codegen.expression import LoopyCCodeMapper
 _registry = {'float32': 'float',
              'int32' : 'int'}
 
+class MyMapper(LoopyCCodeMapper):
+    var_subst_map = {}
+
 def dune_function_manglers():
     # OpenCL example impls: target/opencl/__init__.py:108
     return []
@@ -38,7 +41,7 @@ class DuneTarget(TargetBase):
 #         raise NotImplementedError()
 
     def get_expression_to_code_mapper(self, codegen_state):
-        return LoopyCCodeMapper(codegen_state)
+        return MyMapper(codegen_state)
 
     def generate_code(self, kernel, codegen_state, impl_arg_info):
         print "Somebody wants me to generate code!"