[Mlir-commits] [mlir] [MLIR] Add verification that symbol operations must not have results (PR #168390)

[Tim Noack]

https://github.com/timnoack created https://github.com/llvm/llvm-project/pull/168390

This patch adds verification to the `SymbolOpInterface` to enforce the design constraint that symbol operations must not produce SSA results, as documented in [Symbols and SymbolTables](https://mlir.llvm.org/docs/SymbolsAndSymbolTables/#defining-or-declaring-a-symbol).

This is a follow-up of #168376

>From b29bf66410292e7fa0b42990fe88e610a97e03f3 Mon Sep 17 00:00:00 2001
From: tn <noack at esa.tu-darmstadt.de>
Date: Mon, 17 Nov 2025 16:40:44 +0100
Subject: [PATCH] [MLIR] Add verification that symbol operations must not have
 results

---
 mlir/include/mlir/IR/SymbolInterfaces.td | 2 ++
 mlir/test/IR/invalid-ops.mlir            | 8 ++++++++
 mlir/test/lib/Dialect/Test/TestOps.td    | 7 +++++++
 3 files changed, 17 insertions(+)

diff --git a/mlir/include/mlir/IR/SymbolInterfaces.td b/mlir/include/mlir/IR/SymbolInterfaces.td
index bbfa30815bd4a..b3aafe063d376 100644
--- a/mlir/include/mlir/IR/SymbolInterfaces.td
+++ b/mlir/include/mlir/IR/SymbolInterfaces.td
@@ -171,6 +171,8 @@ def Symbol : OpInterface<"SymbolOpInterface"> {
     if (concreteOp.isDeclaration() && concreteOp.isPublic())
       return concreteOp.emitOpError("symbol declaration cannot have public "
              "visibility");
+    if ($_op->getNumResults() != 0)
+      return concreteOp.emitOpError("symbols must not have results");
     auto parent = $_op->getParentOp();
     if (parent && !parent->hasTrait<OpTrait::SymbolTable>() && parent->isRegistered()) {
       return concreteOp.emitOpError("symbol's parent must have the SymbolTable "
diff --git a/mlir/test/IR/invalid-ops.mlir b/mlir/test/IR/invalid-ops.mlir
index 0c5fec8c4055a..2f5dd28b51911 100644
--- a/mlir/test/IR/invalid-ops.mlir
+++ b/mlir/test/IR/invalid-ops.mlir
@@ -145,3 +145,11 @@ func.func @verify_fail_3() {
   %r = "arith.constant"() {value = -3 : si32} : () -> si32
   return
 }
+
+// -----
+
+// Verify that symbols with results are rejected
+module {
+  // expected-error at +1 {{'test.symbol_with_result' op symbols must not have results}}
+  %0 = "test.symbol_with_result"() <{sym_name = "test_symbol"}> : () -> i32
+}
diff --git a/mlir/test/lib/Dialect/Test/TestOps.td b/mlir/test/lib/Dialect/Test/TestOps.td
index 275025978a784..670223984fd95 100644
--- a/mlir/test/lib/Dialect/Test/TestOps.td
+++ b/mlir/test/lib/Dialect/Test/TestOps.td
@@ -120,6 +120,13 @@ def SymbolOp : TEST_Op<"symbol", [NoMemoryEffect, Symbol]> {
                        OptionalAttr<StrAttr>:$sym_visibility);
 }
 
+def SymbolWithResultOp : TEST_Op<"symbol_with_result", [Symbol]> {
+  let summary = "invalid symbol operation that produces an SSA result";
+  let arguments = (ins StrAttr:$sym_name,
+                       OptionalAttr<StrAttr>:$sym_visibility);
+  let results = (outs AnyType:$result);
+}
+
 def OverriddenSymbolVisibilityOp : TEST_Op<"overridden_symbol_visibility", [
   DeclareOpInterfaceMethods<Symbol, ["getVisibility", "setVisibility"]>,
 ]> {