[llvm][MetadataLoader] Make sure we correctly load DW_APPLE_ENUM_KIND from bitcode (#132374)

This was pointed out in
#124752 (comment)

There was no test that roundtrips this attribute through LLVM bitcode,
so this was never caught.

Author: Michael137

llvm/lib/Bitcode/Reader/MetadataLoader.cpp

@@ -1704,8 +1704,8 @@ Error MetadataLoader::MetadataLoaderImpl::parseOneMetadata(
       }
     }
 
-    if (Record.size() > 25 && Record[25] != dwarf::DW_APPLE_ENUM_KIND_invalid)
-      EnumKind = Record[25];
+    if (Record.size() > 24 && Record[24] != dwarf::DW_APPLE_ENUM_KIND_invalid)
+      EnumKind = Record[24];
 
     DICompositeType *CT = nullptr;
     if (Identifier)

llvm/test/Bitcode/DW_AT_APPLE_enum_kind.ll

@@ -0,0 +1,42 @@
+; RUN: llvm-as < %s | llvm-dis | llvm-as | llvm-dis | FileCheck %s --check-prefix=CHECK-METADATA
+
+; C++ source to regenerate:
+; enum __attribute__((enum_extensibility(open))) OpenEnum {
+;   oe1
+; } oe;
+; 
+; enum __attribute__((enum_extensibility(closed))) ClosedEnum {
+;   ce1
+; } ce;
+; 
+; $ clang++ -O0 -g debug-info-enum-kind.cpp -c
+
+; CHECK-METADATA: enumKind: DW_APPLE_ENUM_KIND_Open
+; CHECK-METADATA: enumKind: DW_APPLE_ENUM_KIND_Closed
+
+source_filename = "enum.cpp"
+target triple = "arm64-apple-macosx"
+
+@oe = global i32 0, align 4, !dbg !0
+@ce = global i32 0, align 4, !dbg !13
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!15, !16}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "oe", scope: !2, file: !3, line: 3, type: !5, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !3, producer: "clang version 21.0.0git", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !12, splitDebugInlining: false, nameTableKind: Apple, sysroot: "/")
+!3 = !DIFile(filename: "enum.cpp", directory: "/tmp")
+!4 = !{!5, !9}
+!5 = !DICompositeType(tag: DW_TAG_enumeration_type, name: "OpenEnum", file: !3, line: 1, baseType: !6, size: 32, elements: !7, identifier: "_ZTS8OpenEnum", enumKind: DW_APPLE_ENUM_KIND_Open)
+!6 = !DIBasicType(name: "unsigned int", size: 32, encoding: DW_ATE_unsigned)
+!7 = !{!8}
+!8 = !DIEnumerator(name: "oe1", value: 0, isUnsigned: true)
+!9 = !DICompositeType(tag: DW_TAG_enumeration_type, name: "ClosedEnum", file: !3, line: 5, baseType: !6, size: 32, elements: !10, identifier: "_ZTS10ClosedEnum", enumKind: DW_APPLE_ENUM_KIND_Closed)
+!10 = !{!11}
+!11 = !DIEnumerator(name: "ce1", value: 0, isUnsigned: true)
+!12 = !{!0, !13}
+!13 = !DIGlobalVariableExpression(var: !14, expr: !DIExpression())
+!14 = distinct !DIGlobalVariable(name: "ce", scope: !2, file: !3, line: 7, type: !9, isLocal: false, isDefinition: true)
+!15 = !{i32 7, !"Dwarf Version", i32 5}
+!16 = !{i32 2, !"Debug Info Version", i32 3}