[MLIR] Add verification that symbol operations must not have results

[timnoack]

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.

This is a follow-up of #168376

[llvmbot]

@llvm/pr-subscribers-mlir
@llvm/pr-subscribers-mlir-core

@llvm/pr-subscribers-mlir-ods

Author: Tim Noack (timnoack)

Changes

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.

This is a follow-up of #168376

---

Full diff: https://github.com/llvm/llvm-project/pull/168390.diff

3 Files Affected:

• (modified) mlir/include/mlir/IR/SymbolInterfaces.td (+2)
• (modified) mlir/test/IR/invalid-ops.mlir (+8)
• (modified) mlir/test/lib/Dialect/Test/TestOps.td (+7)

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 = $_op->getParentOp();
     if (parent && !parent->hasTrait<OpTrait::SymbolTable>() && parent->isRegistered()) {
       return concreteOp.emitOpError("symbol's parent must have the SymbolTable "
diff --git a/mlir/test/IR/invalid-ops.mlir b/mlir/test/IR/invalid-ops.mlir
index 0c5fec8c4055a..2f5dd28b51911 100644
--- a/mlir/test/IR/invalid-ops.mlir
+++ b/mlir/test/IR/invalid-ops.mlir
@@ -145,3 +145,11 @@ func.func @verify_fail_3() {
   %r = "arith.constant"() {value = -3 : si32} : () -> si32
   return
 }
+
+// -----
+
+// Verify that symbols with results are rejected
+module {
+  // expected-error@+1 {{'test.symbol_with_result' op symbols must not have results}}
+  %0 = "test.symbol_with_result"() <{sym_name = "test_symbol"}> : () -> i32
+}
diff --git a/mlir/test/lib/Dialect/Test/TestOps.td b/mlir/test/lib/Dialect/Test/TestOps.td
index 275025978a784..670223984fd95 100644
--- a/mlir/test/lib/Dialect/Test/TestOps.td
+++ b/mlir/test/lib/Dialect/Test/TestOps.td
@@ -120,6 +120,13 @@ def SymbolOp : TEST_Op<"symbol", [NoMemoryEffect, Symbol]> {
                        OptionalAttr<StrAttr>:$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"]>,
 ]> {