[mlir][async] Avoid crash when not using func.func (#72801)

The `createParallelComputeFunction` crashed when calling
`getFunctionTypeAttrName` during the creation of a new `FuncOp` inside
the pass. The problem is that `getFunctionTypeAttrName` looks up the
attribute name for the function type which in this case is `func.func`.
However, `name.getAttributeNames()` was empty when clients used
`llvm.func` instead of `func.func`.

To fix this, the `func` dialect is now registered as a dependent
dialect. Also, I've added an assertion which could save other people
some time.

Fixes #71281, fixes #64326.

Author: rikhuijzer

mlir/include/mlir/Dialect/Async/Passes.td

@@ -36,6 +36,7 @@ def AsyncParallelFor : Pass<"async-parallel-for", "ModuleOp"> {
   let dependentDialects = [
     "arith::ArithDialect",
     "async::AsyncDialect",
+    "func::FuncDialect",
     "scf::SCFDialect"
   ];
 }

mlir/test/Dialect/Async/async-parallel-for-compute-fn.mlir

@@ -69,6 +69,25 @@ func.func @sink_constant_step(%arg0: memref<?xf32>, %lb: index, %ub: index) {
 
 // -----
 
+// Smoke test that parallel for doesn't crash when func dialect is not used.
+
+// CHECK-LABEL: llvm.func @without_func_dialect()
+llvm.func @without_func_dialect() {
+  %cst = arith.constant 0.0 : f32
+
+  %c0 = arith.constant 0 : index
+  %c22 = arith.constant 22 : index
+  %c1 = arith.constant 1 : index
+  %54 = memref.alloc() : memref<22xf32>
+  %alloc_4 = memref.alloc() : memref<22xf32>
+  scf.parallel (%arg0) = (%c0) to (%c22) step (%c1) {
+    memref.store %cst, %alloc_4[%arg0] : memref<22xf32>
+  }
+  llvm.return
+}
+
+// -----
+
 // Check that for statically known inner loop bound block size is aligned and
 // inner loop uses statically known loop trip counts.
 

mlir/tools/mlir-tblgen/OpDefinitionsGen.cpp

@@ -1143,6 +1143,8 @@ void OpEmitter::genAttrNameGetters() {
       const char *const getAttrName = R"(
   assert(index < {0} && "invalid attribute index");
   assert(name.getStringRef() == getOperationName() && "invalid operation name");
+  assert(name.isRegistered() && "Operation isn't registered, missing a "
+        "dependent dialect loading?");
   return name.getAttributeNames()[index];
 )";
       method->body() << formatv(getAttrName, attributes.size());