[mlir][assemblyFormat] Fix bug when using AttrSizedOperandSegments trait with only non-buildable operand types

Summary:
When creating an operation with
* `AttrSizedOperandSegments` trait
* Variadic operands of only non-buildable types
* assemblyFormat to automatically generate the parser
the `builder` local variable is used, but never declared.
This adds a fix as well as a test for this case as existing ones use buildable types only.

Reviewers: rriddle, Kayjukh, grosser

Reviewed By: Kayjukh

Subscribers: mehdi_amini, jpienaar, shauheen, antiagainst, nicolasvasilache, arpith-jacob, mgester, lucyrfox, liufengdb, Joonsoo, grosul1, frgossen, llvm-commits

Tags: #mlir, #llvm

Differential Revision: https://reviews.llvm.org/D79004

mlir/test/lib/Dialect/Test/TestOps.td

@@ -1258,6 +1258,16 @@ def FormatOptionalOperandResultBOp : FormatOptionalOperandResultOpBase<"b", [{
   (`[` $variadic^ `]`)? attr-dict
 }]>;
 
+def FormatTwoVariadicOperandsNoBuildableTypeOp
+    : TEST_Op<"format_two_variadic_operands_no_buildable_type_op",
+              [AttrSizedOperandSegments]> {
+  let arguments = (ins Variadic<AnyType>:$a,
+                       Variadic<AnyType>:$b);
+  let assemblyFormat = [{
+    `(` $a `:` type($a) `)` `->` `(` $b `:` type($b) `)`  attr-dict
+  }];
+}
+
 //===----------------------------------------------------------------------===//
 // Test SideEffects
 //===----------------------------------------------------------------------===//

mlir/tools/mlir-tblgen/OpFormatGen.cpp

@@ -741,10 +741,8 @@ void OperationFormat::genParserTypeResolution(Operator &op,
 
   // Initialize the set of buildable types.
   if (!buildableTypes.empty()) {
-    body << "  Builder &builder = parser.getBuilder();\n";
-
     FmtContext typeBuilderCtx;
-    typeBuilderCtx.withBuilder("builder");
+    typeBuilderCtx.withBuilder("parser.getBuilder()");
     for (auto &it : buildableTypes)
       body << "  Type odsBuildableType" << it.second << " = "
            << tgfmt(it.first, &typeBuilderCtx) << ";\n";
@@ -867,7 +865,7 @@ void OperationFormat::genParserVariadicSegmentResolution(Operator &op,
                                                          OpMethodBody &body) {
   if (!allOperands && op.getTrait("OpTrait::AttrSizedOperandSegments")) {
     body << "  result.addAttribute(\"operand_segment_sizes\", "
-         << "builder.getI32VectorAttr({";
+         << "parser.getBuilder().getI32VectorAttr({";
     auto interleaveFn = [&](const NamedTypeConstraint &operand) {
       // If the operand is variadic emit the parsed size.
       if (operand.isVariableLength())