Don't use CorrMM when there is no c compiler (no perform, it will fallback to…

theano/tensor/nnet/opt.py

@@ -61,6 +61,8 @@ compile.optdb.register('local_inplace_sparse_block_outer',
 # Conv opts
 @local_optimizer([AbstractConv2d])
 def local_abstractconv_gemm(node):
+    if theano.config.cxx == "":
+        return
     if not isinstance(node.op, AbstractConv2d):
         return None
     img, kern = node.inputs
@@ -79,6 +81,8 @@ def local_abstractconv_gemm(node):
 
 @local_optimizer([AbstractConv2d_gradWeights])
 def local_abstractconv_gradweight_gemm(node):
+    if theano.config.cxx == "":
+        return
     if not isinstance(node.op, AbstractConv2d_gradWeights):
         return None
     img, topgrad, shape = node.inputs
@@ -98,6 +102,8 @@ def local_abstractconv_gradweight_gemm(node):
 
 @local_optimizer([AbstractConv2d_gradInputs])
 def local_abstractconv_gradinputs_gemm(node):
+    if theano.config.cxx == "":
+        return
     if not isinstance(node.op, AbstractConv2d_gradInputs):
         return None
     kern, topgrad, shape = node.inputs