[DAPHNE-#793] Prevent merging transpose into initial SPGEMM

This commit adds a quick fix to not merge transpose operations into sparse matrix multiplication as our CPP kernels can not handle this. The temporary workaround until we support transposition uses a hard coded sparsity threshold as there is no user config available in the canonicalization. The matrix representation selection functionality would also be a suitable measure but is not implemented in a suitable way for this at the moment.

Author: corepointer

src/compiler/execution/DaphneIrExecutor.cpp

@@ -131,9 +131,11 @@ bool DaphneIrExecutor::runPasses(mlir::ModuleOp module) {
     pm.addNestedPass<mlir::func::FuncOp>(mlir::daphne::createInferencePass());
     pm.addPass(mlir::createCanonicalizerPass());
 
-    if (selectMatrixRepresentations_)
-        pm.addNestedPass<mlir::func::FuncOp>(
-            mlir::daphne::createSelectMatrixRepresentationsPass(userConfig_));
+    if (selectMatrixRepresentations_) {
+        pm.addNestedPass<mlir::func::FuncOp>(mlir::daphne::createSelectMatrixRepresentationsPass(userConfig_));
+        pm.addNestedPass<mlir::func::FuncOp>(mlir::createCanonicalizerPass());
+    }
+
     if (userConfig_.explain_select_matrix_repr)
         pm.addPass(mlir::daphne::createPrintIRPass(
             "IR after selecting matrix representations:"));

src/ir/daphneir/DaphneDialect.cpp

@@ -1119,6 +1119,15 @@ mlir::LogicalResult mlir::daphne::MatMulOp::canonicalize(
         return mlir::failure();
     }
 
+    // ToDo: This check prevents merging transpose into matrix multiplication because that is not yet supported by our
+    //   sparse kernels.
+    // ToDo: bring user config here for sparsity threshold or properly use MatrixRepresentation
+    if(auto t = rhs.getType().dyn_cast<mlir::daphne::MatrixType>()) {
+        auto sparsity = t.getSparsity();
+        if(sparsity < 0.25)
+            return mlir::failure();
+    }
+
 #if 0
     // TODO Adapt PhyOperatorSelectionPass once this code is turned on again.
     if(lhsTransposeOp) {