[Mlir-commits] [mlir] [mlir] Walk nested non-symbol table ops in symbol dce (PR #143353)

[Jacques Pienaar]

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@@ -108,15 +112,42 @@ LogicalResult SymbolDCE::computeLiveness(Operation *symbolTableOp,
   // that are referenced within.
   while (!worklist.empty()) {
     Operation *op = worklist.pop_back_val();
+    LLVM_DEBUG(llvm::dbgs() << "processing: " << op->getName() << "\n");
 
     // If this is a symbol table, recursively compute its liveness.
     if (op->hasTrait<OpTrait::SymbolTable>()) {
       // The internal symbol table is hidden if the parent is, if its not a
       // symbol, or if it is a private symbol.
       SymbolOpInterface symbol = dyn_cast<SymbolOpInterface>(op);
       bool symIsHidden = symbolTableIsHidden || !symbol || symbol.isPrivate();
+      LLVM_DEBUG(llvm::dbgs() << "\tsymbol table: " << op->getName()
+                              << " is hidden: " << symIsHidden << "\n");
       if (failed(computeLiveness(op, symbolTable, symIsHidden, liveSymbols)))
         return failure();
+    } else {
+      LLVM_DEBUG(llvm::dbgs()
+                 << "\tnon-symbol table: " << op->getName() << " is hidden\n");
+      // If the op is not a symbol table, then, unless op itself is dead which
+      // would be handled by DCE, we need to check all the regions and blocks
+      // within the op to find the uses (e.g., consider visibility within op as
+      // if top level rather than relying on pure symbol table visibility). This
+      // is more conservative than SymbolTable::walkSymbolTables in the case
+      // where there is again SymbolTable information to take advantage of.
+      for (auto &region : op->getRegions()) {
+        for (auto &block : region.getBlocks()) {
+          for (Operation &op : block) {
+            SymbolOpInterface symbol = dyn_cast<SymbolOpInterface>(&op);
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jpienaar wrote:

That's a good point, I was just treating it like a top, but I can just always add as it shouldn't happen, so can just add unconditionally. Simplified, thanks

https://github.com/llvm/llvm-project/pull/143353