[AlterOpLayout][x86] NHWC to NCHWc conv support. (#4080)

topi/python/topi/x86/conv2d_alter_op.py

@@ -158,7 +158,6 @@ def _alter_conv2d_layout(attrs, inputs, tinfo, F):
             return None
         return F.nn.contrib_conv2d_nchwc_int8(*copy_inputs, **new_attrs)
 
-    if data_layout == 'NCHW' and attrs['kernel_layout'] == 'OIHW':
     # (oc, ic, h, w) -> (OC, IC, h, w, ic, oc)
     new_attrs['kernel_layout'] = 'OIHW%di%do' % (ic_bn, oc_bn)
     # Store altered operator's config
@@ -172,7 +171,6 @@ def _alter_conv2d_layout(attrs, inputs, tinfo, F):
     if F.__name__ == 'nnvm.symbol':
         return F.contrib.conv2d_NCHWc(*copy_inputs, **new_attrs)
     return F.nn.contrib_conv2d_nchwc(*copy_inputs, **new_attrs)
-    return None
 
 
 @conv2d_legalize.register("cpu")