[mlir][llvm] Make DINamespace name optional

[Dinistro]

Summary

This commit makes the name of a DINamespace optional to enable modeling
of anonymous namespaces.

[gysit]

Thanks!

mlir/include/mlir/Dialect/LLVMIR/LLVMAttrDefs.td

 
 //===----------------------------------------------------------------------===//
 // DINamespaceAttr
 //===----------------------------------------------------------------------===//
 
 def LLVM_DINamespaceAttr : LLVM_Attr<"DINamespace", "di_namespace",
                                       /*traits=*/[], "DIScopeAttr"> {
   let parameters = (ins
-    "StringAttr":$name,
+    OptionalParameter<"StringAttr">:$name,
     OptionalParameter<"DIScopeAttr">:$scope,
     "bool":$exportSymbols
   );
 
   let assemblyFormat = "`<` struct(params) `>`";
 }
 
 //===----------------------------------------------------------------------===//

mlir/test/Dialect/LLVMIR/debuginfo.mlir

#toplevel_namespace = #llvm.di_namespace<
   name = "toplevel", exportSymbols = true
 >
 
 // CHECK-DAG: #[[NESTED:.*]] = #llvm.di_namespace<name = "nested", scope = #[[TOPLEVEL]], exportSymbols = false>
 #nested_namespace = #llvm.di_namespace<
   name = "nested", scope = #toplevel_namespace, exportSymbols = false
 >
 
+// CHECK-DAG: #[[ANONYMOUS_NS:.*]] = #llvm.di_namespace<scope = #[[FILE]], exportSymbols = false>
+#anonymous_namespace = #llvm.di_namespace<
+  scope = #file,
+  exportSymbols = false
+>
+
 // CHECK-DAG: #[[COMP2:.*]] = #llvm.di_composite_type<tag = DW_TAG_class_type, name = "class_name", file = #[[FILE]], scope = #[[NESTED]], flags = "TypePassByReference|NonTrivial">
 #comp2 = #llvm.di_composite_type<
   tag = DW_TAG_class_type, name = "class_name", file = #file, scope = #nested_namespace,
   flags = "TypePassByReference|NonTrivial"
 >
 
 // CHECK-DAG: #[[SPTYPE0:.*]] = #llvm.di_subroutine_type<callingConvention = DW_CC_normal, types = #[[NULL]], #[[INT0]], #[[PTR0]], #[[PTR1]], #[[COMP0:.*]], #[[COMP1:.*]], #[[COMP2:.*]]>
 #spType0 = #llvm.di_subroutine_type<
   callingConvention = DW_CC_normal, types = #null, #int0, #ptr0, #ptr1, #comp0, #comp1, #comp2
 >
 
 // CHECK-DAG: #[[SPTYPE1:.*]] = #llvm.di_subroutine_type<types = #[[INT1]], #[[INT1]]>
 #spType1 = #llvm.di_subroutine_type<
   // Omit the optional callingConvention parameter.
   types = #int1, #int1
 >
 
 // CHECK-DAG: #[[SPTYPE2:.*]] = #llvm.di_subroutine_type<callingConvention = DW_CC_normal>
 #spType2 = #llvm.di_subroutine_type<
   // Omit the optional types parameter array.
   callingConvention = DW_CC_normal
 >
 
-// CHECK-DAG: #[[SP0:.*]] = #llvm.di_subprogram<compileUnit = #[[CU]], scope = #[[FILE]], name = "addr", linkageName = "addr", file = #[[FILE]], line = 3, scopeLine = 3, subprogramFlags = "Definition|Optimized", type = #[[SPTYPE0]]>
+// CHECK-DAG: #[[SP0:.*]] = #llvm.di_subprogram<compileUnit = #[[CU]], scope = #[[ANONYMOUS_NS]], name = "addr", linkageName = "addr", file = #[[FILE]], line = 3, scopeLine = 3, subprogramFlags = "Definition|Optimized", type = #[[SPTYPE0]]>
 #sp0 = #llvm.di_subprogram<
-  compileUnit = #cu, scope = #file, name = "addr", linkageName = "addr",
+  compileUnit = #cu, scope = #anonymous_namespace, name = "addr", linkageName = "addr",
   file = #file, line = 3, scopeLine = 3, subprogramFlags = "Definition|Optimized", type = #spType0
 >
 
 // CHECK-DAG: #[[SP1:.*]] = #llvm.di_subprogram<compileUnit = #[[CU]], scope = #[[COMP2]], name = "value", file = #[[FILE]], subprogramFlags = Definition, type = #[[SPTYPE1]]>
 #sp1 = #llvm.di_subprogram<
   // Omit the optional linkageName parameter.
   compileUnit = #cu, scope = #comp2, name = "value",
   file = #file, subprogramFlags = "Definition", type = #spType1