replace greedy pattern rewrites with partial conversions

better failure messages

src/PIM/Conversion/SpatialToGraphviz/SpatialToGraphviz.cpp

@@ -202,6 +202,7 @@ void SpatialToGraphvizPass::runOnOperation() {
 
   auto entryFunc = getPimEntryFunc(module);
   if (failed(entryFunc)) {
+    module.emitError("failed to locate the PIM entry function for Spatial graph visualization");
     signalPassFailure();
     return;
   }