Use symbol-DCE pass instead of inefficient custom code

Author: ftynse

lib/polygeist/Passes/ParallelLower.cpp

@@ -520,14 +520,6 @@ void ParallelLower::runOnOperation() {
     }
   });
 
-  auto ST = symbolTable.getSymbolTable(getOperation());
-  for (auto f : toErase) {
-    bool empty = ST.symbolKnownUseEmpty(f, getOperation());
-    if (empty) {
-      f->erase();
-    }
-  }
-
   // Fold the copy memtype cast
   {
     mlir::RewritePatternSet rpl(getOperation()->getContext());

tools/mlir-clang/mlir-clang.cc

@@ -487,6 +487,7 @@ int main(int argc, char **argv) {
       mlir::OpPassManager &optPM = pm.nest<mlir::FuncOp>();
       optPM.addPass(mlir::createCanonicalizerPass());
       pm.addPass(polygeist::createParallelLowerPass());
+      pm.addPass(mlir::createSymbolDCEPass());
       mlir::OpPassManager &noptPM = pm.nest<mlir::FuncOp>();
       noptPM.addPass(mlir::createCanonicalizerPass());
       noptPM.addPass(polygeist::createMem2RegPass());